View source for Earth:Air pollution

{{Short description|Presence of dangerous substances in the atmosphere}}

[[File:AlfedPalmersmokestacks.jpg|thumb|upright=1.2|Air pollution from a [[Chemistry:Coke (fuel)|coking oven]]]]
[[File:2016 EPI Environmental Health Objective - Air Quality (26170609658).jpg|thumb|upright=2|2016 Environmental Performance Index – darker colors indicate lower concentrations of fine particulate matter and nitrogen dioxide, as well as better indoor air quality.]]
[[File:Air pollution death rates.png|thumb|Deaths from air pollution per 100,000 inhabitants (IHME, 2019)]]
{{Weather}}

'''Air pollution''' is the contamination of air due to the presence of substances called pollutants in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials.<ref name="Air pollution" /> It is also the contamination of the indoor or outdoor environment either by chemical, physical, or biological agents that alters the natural features of the atmosphere.<ref name="Air pollution">{{Cite web |title=Air pollution |url=https://www.who.int/health-topics/air-pollution |access-date=2023-01-14 |website= www.who.int |language=en}}</ref> There are many different types of air pollutants, such as gases (including [[Chemistry:Ammonia|ammonia]], [[Chemistry:Carbon monoxide|carbon monoxide]], [[Chemistry:Sulfur dioxide|sulfur dioxide]], [[Earth:NOx|nitrous oxides]], [[Chemistry:Methane|methane]] and chlorofluorocarbons), [[Earth:Particulates|particulates]] (both organic and inorganic), and [[Physics:Biomolecule|biological molecules]]. Air pollution can cause diseases, allergies, and even death to humans; it can also cause harm to other living organisms such as animals and crops, and may damage the natural environment (for example, [[Earth:Climate change|climate change]], [[Earth:Ozone depletion|ozone depletion]] or habitat degradation) or built environment (for example, [[Earth:Acid rain|acid rain]]).<ref name="auto1">{{Cite journal |last1=Manisalidis |first1=Ioannis |last2=Stavropoulou |first2=Elisavet |last3=Stavropoulos |first3=Agathangelos |last4= Bezirtzoglou |first4=Eugenia |date=2020 |title=Environmental and Health Impacts of Air Pollution: A Review |journal=Frontiers in Public Health |volume=8 |page=14 |doi= 10.3389/fpubh.2020.00014 |issn=2296-2565 |pmc=7044178 |pmid=32154200 |doi-access=free}}</ref> Air pollution can be caused by both human activities<ref>{{cite book|first1=Rachel |last1=Howell |first2= Jenny |last2=Pickerill |chapter=The Environment and Environmentalism |editor1-first=Peter |editor1-last=Daniels |editor2-first=Michael |editor2-last=Bradshaw |editor2-link= Michael J. Bradshaw |editor3-first=Denis |editor3-last=Shaw |editor4-first=James |editor4-last=Sidaway |editor5-first=Tim |editor5-last=Hall |title=An Introduction To Human Geography |publisher= Pearson |edition=5th |date=2016 |page=134 |isbn=978-1-292-12939-6}}</ref> and natural phenomena.<ref>{{Citation |last1=Dimitriou |first1=Anastasia |title=Causes and Consequences of Air Pollution and Environmental Injustice as Critical Issues for Science and Environmental Education |date=2011-09-26 |url=http://www.intechopen.com/books/the-impact-of-air-pollution-on-health-economy-environment-and-agricultural-sources/causes-and-consequences-of-air-pollution-and-environmental-injustice-as-critical-issues-for-science- |work=The Impact of Air Pollution on Health, Economy, Environment and Agricultural Sources |editor-last=Khallaf |editor-first=Mohamed |publisher=InTech |language=en |doi=10.5772/17654 |isbn=978-953-307-528-0 |access-date=2022-05-31 |last2=Christidou |first2=Vasilia}}</ref>

Air quality is closely related to the earth's climate and [[Earth:Ecosystem|ecosystem]]s globally. Many of the contributors of air pollution are also sources of [[Earth:Greenhouse gas emissions|greenhouse emission]] i.e., burning of fossil fuel.<ref name="Air pollution"/>

Air pollution is a significant risk factor for a number of pollution-related diseases, including respiratory infections, heart disease, [[Medicine:Chronic obstructive pulmonary disease|chronic obstructive pulmonary disease]] (COPD), [[Medicine:Stroke|stroke]], and lung cancer.<ref name="WHO2014"/> Growing evidence suggests that air pollution exposure may be associated with reduced IQ scores, impaired cognition,<ref>{{cite journal |last1=Allen |first1=J. L. |last2=Klocke |first2=C. |last3=Morris-Schaffer |first3=K. |last4=Conrad |first4=K. |last5=Sobolewski |first5=M. |last6=Cory-Slechta |first6=D. A. |title=Cognitive Effects of Air Pollution Exposures and Potential Mechanistic Underpinnings |journal=Current Environmental Health Reports |date=June 2017 |volume=4 |issue=2 |pages=180–191 |doi=10.1007/s40572-017-0134-3 |pmid=28435996 |pmc=5499513 |language=en}}</ref> increased risk for psychiatric disorders such as [[Medicine:Depression (mood)|depression]]<ref>{{Cite journal |last1=Newbury |first1=Joanne B. |last2=Stewart |first2=Robert |last3=Fisher |first3=Helen L. |last4=Beevers |first4=Sean |last5=Dajnak |first5=David |last6=Broadbent |first6=Matthew |last7=Pritchard |first7=Megan |last8=Shiode |first8=Narushige |last9=Heslin |first9=Margaret |last10=Hammoud |first10=Ryan |last11=Hotopf |first11=Matthew |title=Association between air pollution exposure and mental health service use among individuals with first presentations of psychotic and mood disorders: retrospective cohort study |journal=The British Journal of Psychiatry |year=2021 |volume=219 |issue=6 |language=en |publication-date=2021-08-19 |pages=678–685 |doi=10.1192/bjp.2021.119 |pmid=35048872 |pmc=8636613 |issn=0007-1250 |doi-access=free}}</ref> and detrimental perinatal health.<ref name="10.1371/journal.pmed.1003718">{{cite journal |last1=Ghosh |first1=Rakesh |last2=Causey |first2=Kate |last3=Burkart |first3=Katrin |last4=Wozniak |first4=Sara |last5=Cohen |first5=Aaron |last6=Brauer |first6=Michael |title=Ambient and household PM2.5 pollution and adverse perinatal outcomes: A meta-regression and analysis of attributable global burden for 204 countries and territories |journal=PLOS Medicine |date=28 September 2021 |volume=18 |issue=9 |pages=e1003718 |doi=10.1371/journal.pmed.1003718 |doi-access=free |pmid=34582444 |pmc=8478226 |language=en |issn=1549-1676}}</ref> The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the [[Biology:Circulatory system|cardiovascular system]]. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to,<ref>{{Cite journal |title=Air Pollution Toxicology—A Brief Review of the Role of the Science in Shaping the Current Understanding of Air Pollution Health Risks |url=https://academic.oup.com/toxsci/article-lookup/doi/10.1093/toxsci/kfq367 |access-date=2022-11-07 |journal=Toxicological Sciences |year=2011 |doi=10.1093/toxsci/kfq367|last1=Stanek |first1=L. W. |last2=Brown |first2=J. S. |last3=Stanek |first3=J. |last4=Gift |first4=J. |last5=Costa |first5=D. L. |volume=120 |pages=S8–S27 |pmid=21147959 }}</ref><ref>{{Cite journal |title=Aerosol physicochemical determinants of carbon black and ozone inhalation co-exposure induced pulmonary toxicity |journal=Toxicological Sciences |year=2022 |doi=10.1093/toxsci/kfac113|last1=Majumder |first1=Nairrita |last2=Kodali |first2=Vamsi |last3=Velayutham |first3=Murugesan |last4=Goldsmith |first4=Travis |last5=Amedro |first5=Jessica |last6=Khramtsov |first6=Valery V. |last7=Erdely |first7=Aaron |last8=Nurkiewicz |first8=Timothy R. |last9=Harkema |first9=Jack R. |last10=Kelley |first10=Eric E. |last11=Hussain |first11=Salik |volume=191 |issue=1 |pages=61–78 |pmid=36303316 |pmc=9887725 }}</ref> the degree of exposure, and the individual's health status and [[Biology:Genetics|genetics]].<ref name="Daniel A. Vallero"/>

Outdoor air pollution attributable to fossil fuel use alone causes ~3.61 million deaths annually, making it one [[Social:List of causes of death by rate|of the top <!--underlying causes-->contributors to human death]],<ref name="WHO2014" /><ref name="PNAS2019">{{Cite journal|title=Effects of fossil fuel and total anthropogenic emission removal on public health and climate |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=116 |issue=15 |pages=7192–7197 |doi=10.1073/pnas.1819989116 |last1=Lelieveld |first1=J. |last2=Klingmüller |first2=K. |last3=Pozzer |first3=A. |last4=Burnett |first4=R. T. |last5=Haines |first5=A. |last6=Ramanathan |first6=V. |s2cid=85515425 |pmc=6462052 |pmid= 30910976 |date=25 March 2019 |bibcode=2019PNAS..116.7192L |doi-access=free}}</ref> with anthropogenic ozone and PM<sub>2.5</sub> causing ~2.1 million.<ref name="spaceref.com">{{Cite web |date=19 September 2013 |title=Fine Particulate Matter Map Shows Premature Mortality Due to Air Pollution - SpaceRef |url=http://spaceref.com/earth/fine-particulate-matter-map-shows-premature-mortality-due-to-air-polution.html |url-status=dead |website=spaceref.com |access-date=12 August 2019 |archive-date=7 December 2022 |archive-url=https://web.archive.org/web/20221207040925/https://spaceref.com/earth/fine-particulate-matter-map-shows-premature-mortality-due-to-air-polution/ }}</ref><ref name="iopscience.iop.org">{{Cite journal|title=Global premature mortality due to anthropogenic outdoor air pollution and the contribution of past climate change |journal=Environmental Research Letters |volume=8 |issue=3 |pages=034005 |doi=10.1088/1748-9326/8/3/034005 |year=2013 |last1=Silva |first1=Raquel A |last2=West |first2=J Jason |last3=Zhang |first3=Yuqiang |last4=Anenberg |first4=Susan C |last5=Lamarque |first5=Jean-François |last6=Shindell |first6=Drew T |last7=Collins |first7=William J |last8=Dalsoren |first8=Stig |last9=Faluvegi |first9=Greg |last10=Folberth |first10=Gerd |last11=Horowitz |first11=Larry W |last12=Nagashima |first12=Tatsuya |last13=Naik |first13=Vaishali |last14=Rumbold |first14=Steven |last15=Skeie |first15=Ragnhild |last16=Sudo |first16=Kengo |last17=Takemura |first17=Toshihiko |last18=Bergmann |first18=Daniel |last19=Cameron-Smith |first19=Philip |last20=Cionni |first20=Irene |last21=Doherty |first21=Ruth M |last22=Eyring |first22=Veronika |last23=Josse |first23=Beatrice |last24=MacKenzie |first24=I A |last25=Plummer |first25=David |last26=Righi |first26=Mattia |last27=Stevenson |first27=David S |last28=Strode |first28=Sarah |last29=Szopa |first29=Sophie |last30=Zeng |first30=Guang |bibcode=2013ERL.....8c4005S |doi-access=free}}</ref> Overall, air pollution causes the deaths of around 7 million people worldwide each year, or a global mean loss of life expectancy (LLE) of 2.9 years,<ref name="10.1093/cvr/cvaa025"/> and is the world's largest single environmental health risk, which has not shown significant progress since at least 2015.<ref name="WHO2014">{{cite web | url =https://www.who.int/news/item/25-03-2014-7-million-premature-deaths-annually-linked-to-air-pollution| title =7 million premature deaths annually linked to air pollution |publisher =WHO|date=25 March 2014| access-date =25 March 2014}}</ref><ref>{{cite web |url=http://www.iea.org/publications/freepublications/publication/WorldEnergyOutlookSpecialReport2016EnergyandAirPollution.pdf |title=Energy and Air Pollution |website=Iea.org |access-date=12 March 2019 |archive-url=https://web.archive.org/web/20191011100229/http://www.iea.org/publications/freepublications/publication/WorldEnergyOutlookSpecialReport2016EnergyandAirPollution.pdf |archive-date=11 October 2019}}</ref><ref>{{cite news |title=Study Links 6.5 Million Deaths Each Year to Air Pollution |url=https://www.nytimes.com/2016/06/27/business/energy-environment/study-links-6-5-million-deaths-each-year-to-air-pollution.html |date=26 June 2016 |work={{wipe|The New York Times}} |access-date=27 June 2016}}</ref><ref name="10.1016/S2542-5196(22)00090-0"/> Indoor air pollution and poor urban air quality are listed as two of the world's worst toxic pollution problems in the 2008 Blacksmith Institute World's Worst Polluted Places report.<ref>{{cite web|url=http://www.worstpolluted.org/ |title=Reports |publisher=WorstPolluted.org |access-date=29 August 2010 |archive-url=https://web.archive.org/web/20100811155338/http://www.worstpolluted.org/ |archive-date= 11 August 2010 |url-status=live}}</ref> The scope of the air pollution crisis is large: In 2018, WHO estimated that "9 out of 10 people breathe air containing high levels of pollutants."<ref name="WHO2018">{{Cite web|title=9 out of 10 people worldwide breathe polluted air, but more countries are taking action |url=https://www.who.int/news/item/02-05-2018-9-out-of-10-people-worldwide-breathe-polluted-air-but-more-countries-are-taking-action |access-date=2021-05-18 |publisher=[[Organization:World Health Organization|World Health Organization]] |language=en |date=2 May 2018 }}</ref> Although the health consequences are extensive, the way the problem is handled is considered largely haphazard<ref>{{Cite web|title=Cheap air pollution monitors help plot your walk |url=https://www.eib.org/en/stories/air-pollution-monitor |access-date=2021-05-18 |website=European Investment Bank |language=en}}</ref><ref name="WHO2018" /><ref>{{Cite web|title=Assessing the risks to health from air pollution |publisher=[[Organization:European Environment Agency|European Environment Agency]] |url=https://www.eea.europa.eu/publications/assessing-the-risks-to-health |access-date=2021-05-18 |website=www.eea.europa.eu |language=en}}</ref> or neglected.<ref name="10.1016/S2542-5196(22)00090-0"/>

[[Finance:Productivity|Productivity]] losses and degraded quality of life caused by air pollution are estimated to cost the [[Finance:World economy|world economy]] $5 trillion per year<ref name="documents.worldbank.org"/><ref name="commondreams.org"/><ref name="Fortune2018"/> but, along with health and mortality impacts, are an [[Finance:Externality|externality]] to the contemporary [[Finance:Economic system|economic system]] and most human activity, albeit sometimes being moderately regulated and monitored.<ref>{{cite journal |last1=Batool |first1=Rubeena |last2=Zaman |first2=Khalid |last3=Khurshid |first3=Muhammad Adnan |last4=Sheikh |first4=Salman Masood |last5=Aamir |first5=Alamzeb |last6=Shoukry |first6=Alaa Mohamd |last7=Sharkawy |first7=Mohamed A. |last8=Aldeek |first8=Fares |last9=Khader |first9=Jameel |last10=Gani |first10=Showkat |title=Economics of death and dying: a critical evaluation of environmental damages and healthcare reforms across the globe |journal=Environmental Science and Pollution Research International |date=October 2019 |volume=26 |issue=29 |pages=29799–29809 |doi=10.1007/s11356-019-06159-x |pmid=31407261 |bibcode=2019ESPR...2629799B |s2cid=199528114 |issn=1614-7499}}</ref><ref>{{cite journal |last1=Bherwani |first1=Hemant |last2=Nair |first2=Moorthy |last3=Musugu |first3=Kavya |last4=Gautam |first4=Sneha |last5=Gupta |first5=Ankit |last6=Kapley |first6=Atya |last7=Kumar |first7=Rakesh |title=Valuation of air pollution externalities: comparative assessment of economic damage and emission reduction under COVID-19 lockdown |journal=Air Quality, Atmosphere & Health |date=10 June 2020 |volume=13 |issue=6 |pages=683–694 |doi=10.1007/s11869-020-00845-3 |pmid=32837611 |pmc=7286556 |bibcode=2020AQAH...13..683B |issn=1873-9318}}</ref> Various pollution control technologies and strategies are available to reduce air pollution.<ref name="Fensterstock1971"/><ref name="Fensterstock1972"/> Several international and national legislation and regulation have been developed to limit the negative effects of air pollution.<ref>{{Cite web |last=US EPA |first=OCSPP |date=2014-09-22 |title=Pollution Prevention Law and Policies |url=https://www.epa.gov/p2/pollution-prevention-law-and-policies |access-date=2022-06-07 |website=www.epa.gov |language=en}}</ref> Local rules, when properly executed, have resulted in significant advances in public health.<ref>{{Cite journal |last=Frieden |first=Thomas R. |date=January 2014 |title=Six Components Necessary for Effective Public Health Program Implementation |journal=American Journal of Public Health |language=en |volume=104 |issue=1 |pages=17–22 |doi=10.2105/AJPH.2013.301608 |issn=0090-0036 |pmc=3910052 |pmid=24228653}}</ref> Some of these efforts have been successful at the international level, such as the Montreal Protocol,<ref>{{Cite web |last=Environment |first=U. N. |date=2018-10-29 |title=About Montreal Protocol |url=http://www.unep.org/ozonaction/who-we-are/about-montreal-protocol |access-date=2022-06-07 |website=Ozonaction |language=en}}</ref> which reduced the release of harmful [[Physics:Ozone layer|ozone]] depleting chemicals, and the 1985 Helsinki Protocol,<ref>{{Cite web |title=The Montreal Protocol on Substances That Deplete the Ozone Layer |url=https://www.state.gov/key-topics-office-of-environmental-quality-and-transboundary-issues/the-montreal-protocol-on-substances-that-deplete-the-ozone-layer/ |access-date=2022-06-07 |website=United States Department of State |language=en-US}}</ref> which reduced sulfur emissions,<ref>{{Cite web |title=Protocol On Further Reduction Of Sulphur Emissions To The Convention On Long-Range Transboundary Air Pollution {{!}} International Environmental Agreements (IEA) Database Project |url=https://iea.uoregon.edu/treaty-text/3186 |access-date=2022-06-07 |website=iea.uoregon.edu |language=en}}</ref> while others, such as [[Earth:Climate change mitigation|international action on climate change]],<ref>{{Cite news |last=Nations |first=United |title=ClimateChange |url=https://www.un.org/en/climatechange |access-date=2022-06-07 |website=United Nations |language=en}}</ref><ref>{{Cite web |title=Climate change |url=https://www.who.int/health-topics/climate-change |access-date=2022-06-07 |website=www.who.int |publisher=[[Organization:World Health Organization|World Health Organization]] |language=en}}</ref><ref>{{Cite web |title=Global Climate Agreements: Successes and Failures |url=https://www.cfr.org/backgrounder/paris-global-climate-change-agreements |access-date=2022-06-07 |website=[[Organization:Council on Foreign Relations|Council on Foreign Relations]] |language=en}}</ref> have been less successful.

== Sources of air pollution ==
===Anthropogenic (human-made) sources===
[[File:Athlone cooling towers demolition 2010-08-22.gif|thumb|Demolition of the cooling towers of a power station, Athlone, Cape Town, South Africa, 2010]]
[[File:BurningOffFieldsInTheEveningInSouthGeorgia.jpg|thumb|Controlled burning of a field outside of Statesboro, Georgia, US, in preparation for spring planting]]
[[File:Fish smoking in Ghana.jpg|thumb|Smoking of fish over an open fire in Ghana, 2018]]
* Stationary sources include:
** fossil-fuel power plants and [[Earth:Biomass (ecology)|biomass]] power plants both have smoke stacks (see for example environmental impact of the coal industry)<ref>{{Cite journal |last=Perera |first=Frederica |date=2017-12-23 |title=Pollution from Fossil-Fuel Combustion is the Leading Environmental Threat to Global Pediatric Health and Equity: Solutions Exist |journal=International Journal of Environmental Research and Public Health |language=en |volume=15 |issue=1 |pages=16 |doi=10.3390/ijerph15010016 |issn=1660-4601 |pmc=5800116 |pmid=29295510 |doi-access=free}}</ref>
*** Oil and gas sites that have methane leaks<ref>{{cite web |title=Mapping methane emissions on a global scale |url=https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-5P/Mapping_methane_emissions_on_a_global_scale |publisher=ESA |archive-url=https://web.archive.org/web/20220203174735/https://www.esa.int/Applications/Observing_the_Earth/Copernicus/Sentinel-5P/Mapping_methane_emissions_on_a_global_scale |archive-date=3 February 2022 |language=en}}</ref><ref>{{cite news |title=Climate change: Satellites map huge methane plumes from oil and gas |url=https://www.bbc.com/news/science-environment-60203683 |access-date=16 March 2022 |work=BBC News |date=4 February 2022}}</ref><ref>{{cite news |title=Cracking down on methane 'ultra emitters' is a quick way to combat climate change, researchers find |url=https://www.washingtonpost.com/climate-environment/2022/02/03/cracking-down-methane-ultra-emitters-is-quick-way-combat-climate-change-researchers-find/ |access-date=16 March 2022 |newspaper={{wipe|The Washington Post}}}}</ref><ref>{{cite journal |last1=Lauvaux |first1=T. |last2=Giron |first2=C. |last3=Mazzolini |first3=M. |last4=d’Aspremont |first4=A. |last5=Duren |first5=R. |last6=Cusworth |first6=D. |last7=Shindell |first7=D. |last8=Ciais |first8=P. |title=Global assessment of oil and gas methane ultra-emitters |journal=Science |date=4 February 2022 |volume=375 |issue=6580 |pages=557–561 |doi=10.1126/science.abj4351 |pmid=35113691 |arxiv=2105.06387 |bibcode=2022Sci...375..557L |s2cid=246530897 |issn=0036-8075 |url=https://www.science.org/doi/10.1126/science.abj4351 |url-access=subscription}}</ref>
** burning of traditional biomass such as wood, crop waste and dung. (In developing and poor countries,<ref>{{cite journal |last1=Rentschler |first1=Jun |last2=Leonova |first2=Nadezda |title=Global air pollution exposure and poverty |journal=Nature Communications |date=2023 |volume=14 |issue=1 |pages=4432 |doi=10.1038/s41467-023-39797-4 |pmid=37481598 |pmc=10363163 |bibcode=2023NatCo..14.4432R |doi-access=free}}</ref> traditional biomass burning is the major source of air pollutants.<ref>{{cite web|title=Biomass Pollution Basics |first1=David |last1=Pennise |first2=Kirk |last2=Smith |publisher=[[Organization:World Health Organization|World Health Organization]] |url=https://www.who.int/indoorair/interventions/antiguamod21.pdf |archive-url=https://web.archive.org/web/20120709001603/http://www.who.int/indoorair/interventions/antiguamod21.pdf |url-status=dead |archive-date=9 July 2012}}</ref><ref>{{cite web|title=Indoor air pollution and household energy |publisher=[[Organization:World Health Organization|WHO]] and UNEP |year=2011 |url=https://www.who.int/heli/risks/indoorair/indoorair/en/index.html}}</ref> It is also the main source of particulate pollution in many developed areas including the UK & New South Wales.<ref>{{cite journal |last1=Hawkes |first1=N. |title=Air pollution in UK: the public health problem that won't go away |journal=BMJ |date=22 May 2015 |volume=350 |issue=may22 1 |pages=h2757 |doi=10.1136/bmj.h2757 |pmid=26001592 |s2cid=40717317}}</ref><ref name="auto">{{Cite web|url=https://www.health.nsw.gov.au/environment/factsheets/Pages/wood-smoke.aspx|title=Wood burning heaters and your health - Fact sheets|website=www.health.nsw.gov.au}}</ref> Its pollutants include [[Astronomy:Polycyclic aromatic hydrocarbon|PAH]]s.<ref>{{cite journal |last1=Tsiodra |first1=Irini |last2=Grivas |first2=Georgios |last3=Tavernaraki |first3=Kalliopi |last4=Bougiatioti |first4=Aikaterini |last5=Apostolaki |first5=Maria |last6=Paraskevopoulou |first6=Despina |last7=Gogou |first7=Alexandra |last8=Parinos |first8=Constantine |last9=Oikonomou |first9=Konstantina |last10=Tsagkaraki |first10=Maria |last11=Zarmpas |first11=Pavlos |last12=Nenes |first12=Athanasios |last13=Mihalopoulos |first13=Nikolaos |title=Annual exposure to polycyclic aromatic hydrocarbons in urban environments linked to wintertime wood-burning episodes |journal=[[Earth:Atmospheric Chemistry and Physics|Atmospheric Chemistry and Physics]] |date=7 December 2021 |volume=21 |issue=23 |pages=17865–17883 |doi=10.5194/acp-21-17865-2021 |doi-access=free |bibcode=2021ACP....2117865T |s2cid=245103794 |language=English |issn=1680-7316}}</ref>)
** manufacturing facilities (factories)<ref>{{cite news |last1=Nace |first1=Trevor |title=China Shuts Down Tens Of Thousands Of Factories In Widespread Pollution Crackdown |url=https://www.forbes.com/sites/trevornace/2017/10/24/china-shuts-down-tens-of-thousands-of-factories-in-widespread-pollution-crackdown/ |access-date=16 June 2022 |work=Forbes |quote="... it is estimated that 40 percent of all China's factories have been shut down at some point in order to be inspected... [and] over 80,000 factories have been hit with fines and criminal offenses as a result of their emissions."}}</ref>
*** a 2014 study found that in China equipment-, machinery-, and devices-manufacturing and construction sectors contributed more than 50% of air pollutant emissions.<ref>{{cite journal |last1=Huo |first1=Hong |last2=Zhang |first2=Qiang |last3=Guan |first3=Dabo |last4=Su |first4=Xin |last5=Zhao |first5=Hongyan |last6=He |first6=Kebin |title=Examining Air Pollution in China Using Production- And Consumption-Based Emissions Accounting Approaches |journal=Environmental Science & Technology |date=16 December 2014 |volume=48 |issue=24 |pages=14139–14147 |doi=10.1021/es503959t |pmid=25401750 |bibcode=2014EnST...4814139H |issn=0013-936X}}</ref>{{better source needed|date=August 2022}} This high emission is due to high [[Earth:Emission intensity|emission intensity]] and high emission factors in its industrial structure.<ref>{{Cite journal |last1=Huo |first1=Hong |last2=Zhang |first2=Qiang |last3=Guan |first3=Dabo |last4=Su |first4=Xin |last5=Zhao |first5=Hongyan |last6=He |first6=Kebin |date=2014-12-16 |title=Examining Air Pollution in China Using Production- And Consumption-Based Emissions Accounting Approaches |url=https://pubs.acs.org/doi/10.1021/es503959t |journal=Environmental Science & Technology |language=en |volume=48 |issue=24 |pages=14139–14147 |doi=10.1021/es503959t |pmid=25401750 |bibcode=2014EnST...4814139H |issn=0013-936X}}</ref>
** construction<ref>{{Cite web|url=https://www.eea.europa.eu/publications/emep-eea-guidebook-2019/part-b-sectoral-guidance-chapters/2-industrial-processes/2-a-mineral-products/2-a-5-b-construction|title=EMEP/EEA air pollutant emission inventory guidebook 2019}}</ref><ref>{{cite web |url=https://www.epa.gov/pm-pollution/particulate-matter-pm-basics |title=Particulate Matter (PM), US EPA|date=19 April 2016 }}</ref>
** waste incineration ([[Engineering:Incineration|incinerators]] as well as open and uncontrolled fires of mismanaged waste, making up about a fourth of municipal solid terrestrial waste)<ref name="waste-crisis">{{cite news |title=Health crisis: Up to a billion tons of waste potentially burned in the open every year |url=https://phys.org/news/2021-01-health-crisis-billion-tons-potentially.html |access-date=13 February 2021 |work=phys.org |language=en}}</ref><ref>{{cite journal |last1=Cook |first1=E. |last2=Velis |first2=C. A. |title=Global Review on Safer End of Engineered Life |journal=Global Review on Safer End of Engineered Life |date=6 January 2021 |url=http://eprints.whiterose.ac.uk/169766/ |access-date=13 February 2021 |language=en}}</ref>
** furnaces and other types of fuel-burning heating devices<ref>{{cite web |title=Combustion Pollutants in Your Home - Guidelines |url=https://ww2.arb.ca.gov/resources/documents/combustion-pollutants-your-home-guidelines |publisher=[[Engineering:California Air Resources Board|California Air Resources Board]] |access-date=16 June 2022 |quote="... most furnaces, wood stoves, fireplaces, gas water heaters, and gas clothes dryers, usually vent (exhaust) the combustion pollutants directly to the outdoors. However, if the vent system is not properly designed, installed, and maintained, indoor pollutants can build up quickly inside the home.}}</ref>
* [[Earth:Mobile source air pollution|Mobile sources]] include [[Earth:Roadway air dispersion modeling|motor vehicles]], Trains (particularly diesel locomotives and DMUs), marine vessels and aircraft<ref>{{cite web |title=Overview of Air Pollution from Transportation |url=https://www.epa.gov/transportation-air-pollution-and-climate-change/overview-air-pollution-transportation |publisher=US Environmental Protection Agency |access-date=16 June 2022 |date=15 December 2021}}</ref> as well as [[Engineering:Rocket|rocket]]s and re-entry of components and [[Astronomy:Space debris|debris]].<ref>{{cite journal |last1=Ryan |first1=Robert G. |last2=Marais |first2=Eloise A. |last3=Balhatchet |first3=Chloe J. |last4=Eastham |first4=Sebastian D. |title=Impact of Rocket Launch and Space Debris Air Pollutant Emissions on Stratospheric Ozone and Global Climate |journal=Earth's Future |date=June 2022 |volume=10 |issue=6 |pages=e2021EF002612 |doi=10.1029/2021EF002612 |pmid=35865359 |pmc=9287058 |bibcode=2022EaFut..1002612R |language=en |issn=2328-4277}}</ref> The [[Earth:Effects of the car on societies#Public or external costs|air pollution externality of cars]] enters the air from the [[Physics:Exhaust gas|exhaust gas]] and car tires (including [[Earth:Microplastics|microplastics]]<ref>{{cite news |last1=Yeung |first1=Jessie |title=Microplastics in our air 'spiral the globe' in a cycle of pollution, study finds |url=https://edition.cnn.com/2021/04/13/world/atmospheric-plastics-study-intl-hnk-scli-scn/index.html |website=CNN |access-date=4 August 2022}}</ref>). Vehicles were reported to be "producing about one-third of all U.S. air pollution"<ref>{{cite news |title=The environmental impacts of cars explained |url=https://www.nationalgeographic.com/environment/article/environmental-impact |archive-url=https://web.archive.org/web/20210305200551/https://www.nationalgeographic.com/environment/article/environmental-impact |url-status=dead |archive-date=5 March 2021 |access-date=4 August 2022 |work=Environment |publisher=National Geographic |date=4 September 2019 |language=en}}</ref>{{better source needed|date=August 2022}} and are a major driver of [[Earth:Climate change|climate change]].<ref>{{cite web |title=NASA GISS: NASA News & Feature Releases:Road Transportation Emerges as Key Driver of Warming |url=https://www.giss.nasa.gov/research/news/20100218a/ |website=www.giss.nasa.gov |access-date=4 August 2022 |language=en}}</ref><ref>{{cite web |title=Car Emissions & Global Warming {{!}} Union of Concerned Scientists |url=https://www.ucsusa.org/resources/car-emissions-global-warming |website=www.ucsusa.org |access-date=4 August 2022 |language=en}}</ref>
* Agriculture and [[Biology:Forest management|forest management]] strategies using controlled burns. Practices like slash-and-burn in forests like the Amazon cause large air pollution with the deforestation.<ref>{{cite web |title=NASA's AIRS Maps Carbon Monoxide from Brazil Fires |url=https://www.jpl.nasa.gov/images/pia23356-nasas-airs-maps-carbon-monoxide-from-brazil-fires |website=NASA Jet Propulsion Laboratory (JPL) |access-date=4 August 2022}}</ref> Controlled or prescribed burning is a practice used in [[Biology:Forest management|forest management]], agriculture, [[Earth:Prairie restoration|prairie restoration]], and [[Chemistry:Greenhouse gas|greenhouse gas]] reduction.<ref>{{Cite journal |last1=Harper |first1=Ashleigh R. |last2=Doerr |first2=Stefan H. |last3=Santin |first3=Cristina |last4=Froyd |first4=Cynthia A. |last5=Sinnadurai |first5=Paul |date=2018-05-15 |title=Prescribed fire and its impacts on ecosystem services in the UK |url=https://www.sciencedirect.com/science/article/pii/S0048969717335878 |journal=Science of the Total Environment |language=en |volume=624 |pages=691–703 |doi=10.1016/j.scitotenv.2017.12.161 |pmid=29272838 |bibcode=2018ScTEn.624..691H |issn=0048-9697}}</ref> Foresters can use controlled fire as a tool because fire is a natural feature of both forest and grassland ecology.<ref>{{Citation |last1=George Neary |first1=Daniel |title=Effects of Fire on Grassland Soils and Water: A Review |date=2020-04-08 |url=https://www.intechopen.com/books/grasses-and-grassland-aspects/effects-of-fire-on-grassland-soils-and-water-a-review |work=Grasses and Grassland Aspects |editor-last=Missiakô Kindomihou |editor-first=Valentin |publisher=IntechOpen |language=en |doi=10.5772/intechopen.90747 |isbn=978-1-78984-949-3 |access-date=2022-06-07 |last2=McMichael Leonard |first2=Jackson |s2cid=213578405}}</ref><ref>{{Cite journal |last1=Husseini |first1=Rikiatu |last2=Aboah |first2=Daniel T. |last3=Issifu |first3=Hamza |date=2020-03-01 |title=Fire control systems in forest reserves: An assessment of three forest districts in the Northern region, Ghana |url=https://www.sciencedirect.com/science/article/pii/S2468227619308063 |journal=Scientific African |language=en |volume=7 |pages=e00245 |doi=10.1016/j.sciaf.2019.e00245 |bibcode=2020SciAf...700245H |s2cid=213400214 |issn=2468-2276}}</ref> Controlled burning encourages the sprouting of some desirable forest trees, resulting in a forest renewal.<ref>{{Cite journal |last1=Reyes |first1=O. |last2=Casal |first2=M. |date=November 2004 |title=Effects of forest fire ash on germination and early growth of four pinus species |url=http://link.springer.com/10.1023/B:VEGE.0000048089.25497.0c |journal=Plant Ecology |language=en |volume=175 |issue=1 |pages=81–89 |doi=10.1023/B:VEGE.0000048089.25497.0c |bibcode=2004PlEco.175...81R |s2cid=20388177 |issn=1385-0237}}</ref>

There are also sources from processes other than combustion:
* Fumes from paint, [[Engineering:Hair spray|hair spray]], varnish, aerosol sprays and other solvents. These can be substantial; emissions from these sources was estimated to account for almost half of pollution from volatile organic compounds in the Los Angeles basin in the 2010s.<ref>{{cite news |url=https://www.npr.org/sections/thetwo-way/2018/02/15/585886321/your-wall-paint-perfumes-and-cleaning-agents-are-polluting-our-air |title=Wall Paint, Perfumes and Cleaning Agents Are Polluting Our Air |newspaper=NPR |date=15 February 2018 |access-date=12 March 2019 |last1=Chatterjee |first1=Rhitu}}</ref>
* Waste deposition in landfills produces [[Chemistry:Methane|methane]]<ref>{{cite web |title=Basic Information about Landfill Gas |url=https://www.epa.gov/lmop/basic-information-about-landfill-gas |website=US Environmental Protection Agency |date=15 April 2016 |access-date=9 August 2022 |quote=Landfill gas (LFG) is a natural byproduct of the decomposition of organic material in landfills. LFG is composed of roughly 50 percent methane...}}</ref> and open burning of waste releases harmful substances.<ref>{{Cite web |date=2023-09-07 |title=Open waste burning prevention {{!}} Climate & Clean Air Coalition |url=https://www.ccacoalition.org/projects/open-waste-burning-prevention |access-date=2023-12-22 |website=www.ccacoalition.org |language=en}}</ref>
* [[Engineering:Nuclear weapon|Nuclear weapon]]s, toxic gases, [[Biology:Biological warfare|germ warfare]], and rocketry are examples of military resources.<ref>{{Citation |last=Hafemeister |first=David |title=Nuclear Proliferation and Terrorism in the Post-9/11 World |chapter=Biological and Chemical Weapons |date=2016 |pages=337–351 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-25367-1_15 |isbn=978-3-319-25365-7 |pmc=7123302}}</ref>
* Agricultural emissions and emissions from meat production or livestock contribute substantially to air pollution<ref>{{cite journal |last1=Sun |first1=Feifei |last2=Dai |first2=Yun |last3=Yu |first3=Xiaohua |title=Air pollution, food production and food security: A review from the perspective of food system |journal=Journal of Integrative Agriculture |date=December 2017 |volume=16 |issue=12 |pages=2945–2962 |doi=10.1016/S2095-3119(17)61814-8}}</ref><ref name="10.1038/nature15371">{{cite journal |last1=Lelieveld |first1=J. |last2=Evans |first2=J. S. |last3=Fnais |first3=M. |last4=Giannadaki |first4=D. |last5=Pozzer |first5=A. |title=The contribution of outdoor air pollution sources to premature mortality on a global scale |journal=Nature |date=September 2015 |volume=525 |issue=7569 |pages=367–371 |doi=10.1038/nature15371 |pmid=26381985 |bibcode=2015Natur.525..367L |s2cid=4460927 |language=en |issn=1476-4687 |quote=Whereas in much of the USA and in a few other countries emissions from traffic and power generation are important, in eastern USA, Europe, Russia and East Asia agricultural emissions make the largest relative contribution to PM2.5, with the estimate of overall health impact depending on assumptions regarding particle toxicity.}}</ref>
** Fertilized farmland may be a major source of [[Chemistry:Nitrogen oxide|nitrogen oxide]]s.<ref>{{cite news|last1=Diep |first1=Francie |title=California's Farms Are an Even Larger Source of Air Pollution Than We Thought |url=https://psmag.com/environment/californias-farms-are-an-even-larger-source-of-air-pollution-than-we-thought |access-date=2 February 2018 |work=Pacific Standard |date=31 January 2018}}</ref>
{{clear}}
{{Bar chart|title=Mean [[Earth:Acid rain|acidifying emissions]] (air pollution) of different foods per 100g of protein<ref name="Nemecek 987–992">{{Cite journal|last1=Nemecek |first1=T. |last2=Poore |first2=J. |s2cid=206664954 |date=1 June 2018 |title=Reducing food's environmental impacts through producers and consumers |journal=Science |volume=360 |issue=6392 |pages=987–992 |doi=10.1126/science.aaq0216 |issn=0036-8075 |pmid=29853680 |bibcode=2018Sci...360..987P |doi-access=free}}</ref>|float=right|label_type=Food Types|data_type=Acidifying Emissions (g SO<sub>2</sub>eq per 100g protein)|bar_width=20|width_units=em|data_max=300.6|label1=Beef|data1=343.6|label2=Cheese|data2=165.5|label3=Pork|data3=142.7|label4=Lamb and mutton|data4=139.0|label5=Farmed crustaceans|data5=133.1|label6=Poultry|data6=102.4|label7=Farmed fish|data7=65.9|label8=Eggs|data8=53.7|label9=[[Biology:Faboideae|Groundnuts]]|data9=22.6|label10=Peas|data10=8.5|label11=Tofu|data11=6.7|label12=|data12=|label13=|data13=}}
{{clear}}

=== Natural sources ===
[[File:Dust Storm Texas 1935.jpg|thumb|Dust storm approaching Stratford, Texas, in 1935]]
* Dust from natural sources, usually large areas of land with little vegetation or no vegetation
* [[Chemistry:Methane|Methane]], emitted by the [[Biology:Digestion|digestion]] of food by animals, for example [[Biology:Cattle|cattle]]
* [[Chemistry:Radon|Radon]] gas from [[Physics:Radioactive decay|radioactive decay]] within the [[Earth:Earth's crust|Earth's crust]]. Radon is a colorless, odorless, naturally occurring, radioactive [[Chemistry:Noble gas|noble gas]] that is formed from the decay of [[Chemistry:Radium|radium]]. It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after [[Engineering:Cigarette|cigarette]] smoking.
* Smoke and [[Chemistry:Carbon monoxide|carbon monoxide]] from wildfires. During periods of active wildfires, smoke from uncontrolled biomass combustion can make up almost 75% of all air pollution by concentration.<ref>{{Cite web |url=https://www.cleanairresources.com/data |title=Education Data, Visualizations & Graphics on particulate pollution. |website=www.cleanairresources.com |access-date=20 March 2019 |archive-date=20 March 2019 |archive-url=https://web.archive.org/web/20190320212032/https://www.cleanairresources.com/data |url-status=dead }}</ref>
* [[Biology:Vegetation|Vegetation]], in some regions, emits environmentally significant amounts of volatile organic compounds (VOCs) on warmer days. These VOCs react with primary anthropogenic pollutants&nbsp;– specifically, NO<sub>x</sub>, SO<sub>2</sub>, and anthropogenic organic carbon compounds&nbsp;– to produce a seasonal haze of secondary pollutants.<ref>{{cite journal|title=Biogenic carbon and anthropogenic pollutants combine to form a cooling haze over the southeastern United States |journal=Proceedings of the National Academy of Sciences |last1=Goldstein |first1=Allen H. |first2=Charles D. |last2=Koven |first3=Colette L. |last3=Heald |first4=Inez Y. |last4=Fung |date=5 May 2009 |doi=10.1073/pnas.0904128106 |pmid=19451635 |volume=106 |issue=22 |pages=8835–40 |pmc=2690056 |bibcode=2009PNAS..106.8835G |doi-access=free}}</ref> Black gum, poplar, oak and [[Biology:Willow|willow]] are some examples of vegetation that can produce abundant VOCs. The VOC production from these species result in ozone levels up to eight times higher than the low-impact tree species.<ref>{{cite journal|title=Trees That Pollute |first=Mark |last=Fischetti |journal=Scientific American |volume=310 |issue=6 |page=14 |doi=10.1038/scientificamerican0614-14 |pmid=25004561 |year=2014 |bibcode=2014SciAm.310f..14F}}</ref>
* [[Earth:Volcano|Volcanic]] activity, which produces [[Chemistry:Sulfur|sulfur]], [[Chemistry:Chlorine|chlorine]], and ash particulates<ref>{{Cite web |title=Volcanic Pollution {{!}} |url=https://intlpollution.commons.gc.cuny.edu/volcanic-pollution/ |access-date=2022-02-27 |language=en-CAC}}</ref>

=== Emission factors ===
[[File:Beijing smog comparison August 2005.png|thumb|upright=2.05|[[Place:Beijing|Beijing]] air in 2005 after rain (left) and a smoggy day (right)]]

Air pollutant emission factors are reported representative values that aim to link the quantity of a pollutant released into the ambient air to an activity connected with that pollutant's release.<ref name="auto1"/><ref>{{Cite web |title=Air Pollution Emissions |url=https://www3.epa.gov/airquality/emission.html |date=2016 |access-date=2022-06-07 |website=US EPA |language=en}}</ref><ref>{{Cite web |last=Environment and Climate Change Canada |title=Air pollutant emissions |url=https://www.canada.ca/en/environment-climate-change/services/environmental-indicators/air-pollutant-emissions.html |access-date=2022-06-07 |website=Canada.ca|date=14 June 2010 }}</ref><ref>{{Cite journal |last1=Manisalidis |first1=Ioannis |last2=Stavropoulou |first2=Elisavet |last3=Stavropoulos |first3=Agathangelos |last4=Bezirtzoglou |first4=Eugenia |date=2020-02-20 |title=Environmental and Health Impacts of Air Pollution: A Review |journal=Frontiers in Public Health |volume=8 |pages=14 |doi=10.3389/fpubh.2020.00014 |issn=2296-2565 |pmc=7044178 |pmid=32154200 |doi-access=free}}</ref> The weight of the pollutant divided by a unit weight, volume, distance, or time of the activity generating the pollutant is how these factors are commonly stated (e.g., kilograms of particulate emitted per tonne of coal burned). These criteria make estimating emissions from diverse sources of pollution easier. Most of the time, these components are just averages of all available data of acceptable quality, and they are thought to be typical of long-term averages.

There are 12 compounds in the list of persistent organic pollutants. Dioxins and [[Chemistry:Furan|furan]]s are two of them and intentionally created by combustion of organics, like open burning of plastics. These compounds are also endocrine disruptors and can mutate the human genes.
[[File:Agbogbloshie,_Ghana_2019.jpg|left|thumb|E-waste processing in [[Agbogbloshie|Agbogbloshie]], Ghana, using open-burning of electronics to access valuable metals like copper. Open burning of plastics is common in many parts of the world without the capacity for processing. Especially without proper protections, heavy metals and other contaminates can seep into the soil, and create water pollution and air pollution.]]
The United States Environmental Protection Agency has published a compilation of air pollutant emission factors for a wide range of industrial sources.<ref>{{cite web|url=http://www.epa.gov/ttn/chief/ap42/index.html |title=AP 42, Volume I |website=US Environmental Protection Agency |access-date=29 August 2010 |archive-url=https://web.archive.org/web/20100924132127/http://www.epa.gov/ttn/chief/ap42/index.html |archive-date=24 September 2010 |url-status=live}}</ref> The United Kingdom, Australia, Canada, and many other countries have published similar compilations, as well as the [[Organization:European Environment Agency|European Environment Agency]].<ref>{{cite web |url=http://www.naei.org.uk/emissions/index.php |title=United Kingdom's emission factor database |website=Naei.org.uk |access-date=29 August 2010 |url-status=dead |archive-url=https://web.archive.org/web/20100707144526/http://www.naei.org.uk/emissions/index.php |archive-date=7 July 2010}}</ref><ref>{{cite web|url=http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009 |title=EMEP/EEA air pollutant emission inventory guidebook—2009 |website=Eea.europa.eu |publisher=European Environmental Agency |date=19 June 2009 |access-date=11 December 2012}}</ref><ref>{{cite web|url=http://www.theenvironmentalblog.org/environmental-issues/environmental-pollution/ |title=Environmental Pollution |website=Theenvironmentalblog.org |date=16 December 2011 |access-date=11 December 2012}}</ref><ref>{{cite web |url=http://www.ipcc-nggip.iges.or.jp/public/gl/invs6.htm |title=Revised 1996 IPCC Guidelines for National Greenhouse Gas Inventories (reference manual) |website=Ipcc-nggip.iges.or.jp |access-date=29 August 2010 |archive-url=https://web.archive.org/web/20080321094829/http://www.ipcc-nggip.iges.or.jp/public/gl/invs6.htm |archive-date=21 March 2008 |url-status=dead}}</ref>

== Pollutants ==
{{Main|Chemistry:Pollutant|Earth:Greenhouse gas emissions}}
[[File:Air Pollution-Causes&Effects.svg|thumb|upright=1.3|Schematic drawing, causes and effects of air pollution: (1) [[Earth:Greenhouse effect|greenhouse effect]], (2) particulate contamination, (3) increased UV radiation, (4) acid rain, (5) increased ground-level ozone concentration, (6) increased levels of nitrogen oxides]]

An air pollutant is a material in the air that can have many effects on humans and the ecosystem.<ref>{{Cite web |last=US EPA |first=OAR |date=2015-12-10 |title=Managing Air Quality - Air Pollutant Types |url=https://www.epa.gov/air-quality-management-process/managing-air-quality-air-pollutant-types |access-date=2022-02-27 |website=www.epa.gov |publisher=US Environmental Protection Agency |language=en}}</ref> The substance can be solid particles, liquid droplets, or gases, and often takes the form of an [[Chemistry:Aerosol|aerosol]] (solid particles or liquid droplets dispersed and carried by a gas).<ref name="Hidy2012">{{cite book | author-first = George|author-last= Hidy | date = 2012 | title = Aerosols: An Industrial and Environmental Science | publisher = Elsevier | page = 1 | isbn = 978-0-323-14251-9 | url = https://books.google.com/books?id=OJxPHYnC9b8C}}</ref> A pollutant can be of natural origin or man-made. Pollutants are classified as primary or secondary. Primary pollutants are usually produced by processes such as ash from a volcanic eruption.

Other examples include carbon monoxide gas from motor vehicle exhausts or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. [[Earth:Ground level ozone|Ground level ozone]] is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants.

===Primary pollutants===
{{Prose|section|date=April 2023}}
Pollutants emitted into the atmosphere by human activity include:
* Ammonia: Emitted mainly by agricultural waste. Ammonia is a compound with the formula NH<sub>3</sub>. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many [[Chemistry:Medication|pharmaceuticals]]. Although in wide use, ammonia is both caustic and hazardous.<ref>{{Cite news|last=Carrington |first=Damian |date=2021-11-04 |title=Ammonia from farms behind 60% of UK particulate air pollution – study |url=https://www.theguardian.com/environment/2021/nov/04/ammonia-from-farms-behind-60-of-uk-particulate-air-pollution-study |access-date=2021-11-07 |work={{wipe|The Guardian}} |language=en}}</ref> In the atmosphere, ammonia reacts with oxides of nitrogen and sulfur to form secondary particles.<ref>{{cite web|title=The Effect of Changing Background Emissions on External Cost Estimates for Secondary Particulates |publisher=Open environmental sciences |year=2008 |url=https://www.researchgate.net/publication/250144316}}</ref>
* [[Chemistry:Carbon dioxide|Carbon dioxide]] ({{CO2}}): Carbon dioxide is a natural component of the atmosphere, essential for plant life and given off by the human respiratory system.<ref>{{cite web|last1=Johnson|first1=Keith|title=How Carbon Dioxide Became a 'Pollutant'|url=https://www.wsj.com/articles/SB124001537515830975|website=Wall Street Journal|date=18 April 2009}}</ref> It is potentially lethal at very high concentrations (typically 100 times "normal" atmospheric levels).<ref name="niosh-co2">{{cite web |title=Carbon dioxide |url=https://www.cdc.gov/niosh/npg/npgd0103.html |website=The National Institute for Occupational Safety and Health (NIOSH) |publisher=U.S. Department of Health & Human Services |access-date=19 April 2023 |date=30 October 2019}}</ref><ref name="hse-co2">{{cite web |title=General hazards of Carbon Dioxide |url=https://www.hse.gov.uk/carboncapture/carbondioxide.htm |website=Health and Safety Executive |publisher=UK Government |access-date=19 April 2023 |quote=For over a century {{CO2}} has been recognised as a workplace hazard at high concentrations. {{CO2}} is naturally present in the air we breathe at a concentration of about 0.037% and is not harmful to health at low concentrations.}}</ref> Although the [[Organization:World Health Organization|World Health Organization]] recognizes {{CO2}} as a climate pollutant, it does not include the gas in its ''Air Quality Guidelines'' or set recommended targets for it.<ref>{{cite book |title=Air Quality Guidelines Global Update 2005: Particulate matter, ozone, nitrogen dioxide and sulfur dioxide |year=2006 |publisher=World Health Organization |location=Copenhagen, Denmark |isbn=92-890-2192-6 |page=12|quote="Some pollutants, and especially those associated with greenhouse warming effects (carbon dioxide, nitrous oxide and methane)..."}}</ref> Because of its role as a [[Chemistry:Greenhouse gas|greenhouse gas]], {{CO2}} has been described as "the worst climate pollutant".<ref>{{cite web|last1=Vaidyanathan |first1=Gayathri |title=The Worst Climate Pollution Is Carbon Dioxide |url=https://www.scientificamerican.com/article/the-worst-climate-pollution-is-carbon-dioxide/ |publisher=Scientific American}}</ref> Statements such as this refer to its long-term atmospheric effects rather than shorter-term effects on such things as human health, food crops, and buildings. This question of terminology has practical consequences, for example, in determining whether the U.S. Clean Air Act (which is designed to improve air quality) is deemed to regulate {{CO2}} emissions.<ref>{{cite web|last1=Barbalace|first1=Roberta C.|title={{CO2}} Pollution and Global Warming: When does carbon dioxide become a pollutant?|url=https://environmentalchemistry.com/yogi/environmental/200611CO2globalwarming.html|date=7 November 2006|website=Environmentalchemistry.com}}</ref> That issue was resolved in the United States by the Inflation Reduction Act of 2022, which specifically amended the Clean Air Act "to define the carbon dioxide produced by the burning of fossil fuels as an 'air pollutant.'"<ref>{{cite news |last1=Friedman |first1=Lisa |title=Democrats Designed the Climate Law to Be a Game Changer. Here's How. |url=https://www.nytimes.com/2022/08/22/climate/epa-supreme-court-pollution.html |access-date=19 April 2023 |work=The New York Times |date=22 August 2022}}</ref> {{CO2}} currently forms about 410 parts per million (ppm) of Earth's atmosphere, compared to about 280&nbsp;ppm in pre-industrial times,<ref>{{cite web|title=Graphic: The relentless rise of carbon dioxide|url=https://climate.nasa.gov/climate_resources/24/|website=Climate Change: Vital Signs of the Planet|publisher=NASA}}</ref> and billions of metric tons of {{CO2}} are emitted annually by burning of fossil fuels.<ref>{{Cite web|title = How much of U.S. carbon dioxide emissions are associated with electricity generation?|url = http://www.eia.gov/tools/faqs/faq.cfm?id=77&t=11|access-date = 16 December 2016}}</ref> {{CO2}} increase in Earth's atmosphere has been accelerating.<ref name="MaunaMonthly">{{cite web|title=Full Mauna Loa {{CO2}} record|url=https://www.esrl.noaa.gov/gmd/ccgg/trends/full.html|website=Earth System Research Laboratory|access-date=10 January 2017}}</ref> {{CO2}} is an [[Chemistry:Asphyxiant gas|asphyxiant gas]] and not classified as toxic or harmful in general.<ref>{{cite web | url=https://www.oecd.org/chemicalsafety/testing/oecdguidelinesforthetestingofchemicals.htm | title=OECD Test Guidelines for Chemicals}}</ref> Workplace exposure limits exist in places like UK (5,000 ppm for long-term exposure and 15,000 ppm for short-term exposure).<ref name="hse-co2" /> Natural disasters like the [[Earth:Limnic eruption|limnic eruption]] at [[Earth:Lake Nyos|Lake Nyos]] can result in a sudden release of huge amount of {{CO2}} as well.<ref>{{cite web | url=https://www.massey.ac.nz/~trauma/issues/2011-1/fomine.htm | title=The Strange Lake Nyos {{CO2}} Gas Disaster: Impacts and The Displacement and Return of Affected Communities}}</ref>
* [[Chemistry:Carbon monoxide|Carbon monoxide]] (CO): CO is a colorless, odorless, toxic gas.<ref>{{Cite web|url=https://www.nhs.uk/conditions/carbon-monoxide-poisoning/|title=Carbon Monoxide Poisoning – NHS|date=17 October 2017}}</ref> It is a product of [[Physics:Combustion|combustion]] of fuel such as natural gas, coal or wood. Vehicular exhaust contributes to the majority of carbon monoxide let into the atmosphere. It creates a smog type formation in the air that has been linked to many lung diseases and disruptions to the natural environment and animals.
* Chlorofluorocarbons (CFCs): Emitted from goods that are now prohibited from use; harmful to the ozone layer. These are gases emitted by air conditioners, freezers, aerosol sprays, and other similar devices. CFCs reach the stratosphere after being released into the atmosphere.<ref>{{Cite web |last=US EPA |first=OAR |date=2017-06-05 |title=Basic Ozone Layer Science |url=https://www.epa.gov/ozone-layer-protection/basic-ozone-layer-science |access-date=2022-06-07 |website=www.epa.gov |publisher=US Environmental Protection Agency |language=en}}</ref> They interact with other gases here, causing harm to the ozone layer. UV rays are able to reach the Earth's surface as a result of this. This can result in skin cancer, eye problems, and even plant damage.<ref>{{Cite web |title=Chlorofluorocarbons (CFCs) are heavier than air, so how do scientists suppose that these chemicals reach the altitude of the ozone layer to adversely affect it? |url=https://www.scientificamerican.com/article/chlorofluorocarbons-cfcs/ |access-date=2022-06-07 |website=Scientific American |language=en}}</ref>
* [[Chemistry:Nitrogen oxide|Nitrogen oxide]]s (NO<sub>x</sub>): Nitrogen oxides, particularly [[Chemistry:Nitrogen dioxide|nitrogen dioxide]], are expelled from high temperature combustion, and are also produced during thunderstorms by [[Physics:Electric discharge|electric discharge]]. They can be seen as a brown [[Earth:Haze|haze]] dome above or a plume downwind of cities. Nitrogen dioxide is a chemical compound with the formula NO<sub>2</sub>. It is one of several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown toxic gas has a characteristic sharp, biting odor.
* Odors: Such as from garbage, sewage, and industrial processes.
* Particulate matter/particles (PM), also known as particulates, atmospheric particulate matter (APM), or fine particles, are microscopic solid or liquid particles suspended in a gas.<ref>{{Cite web |title=What is Particulate Matter? {{!}} Urban Environmental Program in New England |url=https://www3.epa.gov/region1/eco/uep/particulatematter.html |access-date=2022-06-07 |website=US EPA |date=March 29, 2022 |language=en |url-status=deviated |archive-url=https://web.archive.org/web/20220607141238/https://www3.epa.gov/region1/eco/uep/particulatematter.html |archive-date= 2022-06-07 }}</ref> Aerosol is a mixture of particles and gas. Volcanoes, [[Earth:Dust storm|dust storm]]s, forest and grassland fires, living plants, and sea spray are all sources of particles. Aerosols are produced by human activities such as the combustion of fossil fuels in automobiles, power plants, and numerous industrial processes.<ref>{{Citation |last1=Munsif |first1=Rabia |title=Industrial Air Emission Pollution: Potential Sources and Sustainable Mitigation |date=2021-01-07 |url=https://www.intechopen.com/books/environmental-emissions/industrial-air-emission-pollution-potential-sources-and-sustainable-mitigation |work=Environmental Emissions |editor-last=Viskup |editor-first=Richard |publisher=IntechOpen |language=en |doi=10.5772/intechopen.93104 |isbn=978-1-83968-510-1 |access-date=2022-06-07 |last2=Zubair |first2=Muhammad |last3=Aziz |first3=Ayesha |last4=Nadeem Zafar |first4=Muhammad |s2cid=234150821}}</ref> Averaged worldwide, anthropogenic aerosols&nbsp;– those made by human activities&nbsp;– currently account for approximately 10% of the atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease,<ref>{{cite web|url=https://www.newsroom.heart.org/index.php?s=43&item=1029 |title=Evidence growing of air pollution's link to heart disease, death |access-date=18 May 2010 |url-status= |archive-url=https://web.archive.org/web/20100603014952if_/http://www.newsroom.heart.org/index.php?s=43&item=1029 |archive-date=3 June 2010}} // American Heart Association. 10 May 2010</ref> altered lung function and lung cancer. Particulates are related to respiratory infections and can be particularly harmful to those with conditions like [[Medicine:Asthma|asthma]].<ref>{{cite journal |last1=Balmes |first1=J.R. |last2=Fine |first2=J.M. |last3=Sheppard |first3=D. |year=1987 |title=Symptomatic bronchoconstriction after short-term inhalation of sulfur dioxide |journal=American Review of Respiratory Disease |volume=136 |issue=5 |pages=1117–21 |doi=10.1164/ajrccm/136.5.1117 |pmid=3674573}}</ref>
* Persistent organic pollutants, which can attach to particulates. Persistent organic pollutants are organic compounds that are resistant to environmental degradation due to chemical, biological, or photolytic processes (POPs). As a result, they've been discovered to survive in the environment, be capable of long-range transmission, bioaccumulate in human and animal tissue, biomagnify in food chains, and pose a major threat to human health and the [[Earth:Ecosystem|ecosystem]].<ref>{{cite book |first1=Ritu |last1=Singh |first2=Sanjeev |last2=Kumar |first3=Susmita |last3=Karmakar |first4=Arif J. |last4=Siddiqui |first5=Ankita |last5=Mathur |first6=Mohd. |last6=Adnan |first7=Vishnu D. |last7=Rajput |first8=Anita |last8=Rani |first9=Narendra |last9=Kumar |editor1-last=Kumar |editor1-first=Narendra |editor2-last=Shukla |editor2-first=Vertika |title=Persistent Organic Pollutants in the Environment: Origin and Role |date=2021 |publisher=CRC Press |isbn=9781003053170 |pages=31–54 |url=https://books.google.com/books?id=NiRAEAAAQBAJ |access-date=11 June 2022 |chapter=2: Causes, Consequences, and Control of Persistent Organic Pollutants}}</ref>
* [[Biology:Radical#Persistent radicals|Persistent free radicals]] connected to airborne fine particles are linked to cardiopulmonary disease.<ref>{{cite web|url=http://www.physorg.com/pdf138201201.pdf |title=Newly detected air pollutant mimics damaging effects of cigarette smoke |website=Physorg.com |access-date=29 August 2010}}</ref><ref>{{cite web|url=https://www.sciencedaily.com/releases/2009/07/090722123751.htm |title=Infant Inhalation Of Ultra-fine Air Pollution Linked To Adult Lung Disease |website=Sciencedaily.com |date=23 July 2009 |access-date=29 August 2010}}</ref>
* [[Astronomy:Polycyclic aromatic hydrocarbon|Polycyclic Aromatic Hydrocarbons]] (PAHs): a group of aromatic compounds formed from the incomplete combustion of organic compounds including coal and oil and tobacco.<ref>{{Cite journal |last1=Kim |first1=Ki-Hyun |last2=Jahan |first2=Shamin Ara |last3=Kabir |first3=Ehsanul |last4=Brown |first4=Richard J. C. |date=2013-10-01 |title=A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects |url=https://www.sciencedirect.com/science/article/pii/S0160412013001633 |journal=Environment International |language=en |volume=60 |pages=71–80 |doi=10.1016/j.envint.2013.07.019 |pmid=24013021 |issn=0160-4120}}</ref>
* Radioactive pollutants: Produced by nuclear explosions, nuclear events, war explosives, and natural processes such as the radioactive decay of radon.
* [[Chemistry:Sulfur oxide|Sulfur oxide]]s (SO<sub>x</sub>): particularly sulfur dioxide, a chemical compound with the formula SO<sub>2</sub>. SO<sub>2</sub> is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide. Further oxidation of SO<sub>2</sub>, usually in the presence of a catalyst such as NO<sub>2</sub>, forms H<sub>2</sub>SO<sub>4</sub>, and thus [[Earth:Acid rain|acid rain]] is formed. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
* Toxic metals, such as [[Chemistry:Lead|lead]] and [[Chemistry:Mercury (element)|mercury]], especially their compounds.
* Volatile organic compounds (VOC): VOCs are both indoor and outdoor air pollutants.<ref name="epa-voc">{{cite web |title=Technical Overview of Volatile Organic Compounds |url=https://www.epa.gov/indoor-air-quality-iaq/technical-overview-volatile-organic-compounds |website=US Environmental Protection Agency |access-date=20 April 2023 |date=14 March 2023}}</ref> They are categorized as either methane (CH<sub>4</sub>) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced [[Earth:Global warming|global warming]]. Other hydrocarbon VOCs are also significant greenhouse gases because of their role in creating ozone and prolonging the life of [[Earth:Atmospheric methane|methane in the atmosphere]]. This effect varies depending on local air quality. The aromatic NMVOCs benzene, toluene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound often associated with industrial use.

===Secondary pollutants===

Secondary pollutants include:
* [[Earth:Ground level ozone|Ground level ozone]] (O<sub>3</sub>): Ozone is created when NOx and VOCs mix. It is a significant part of the troposphere.<ref>{{Cite book |url=https://www.nap.edu/read/1889/chapter/8 |title=Read "Rethinking the Ozone Problem in Urban and Regional Air Pollution" at NAP.edu |year=1991 |doi=10.17226/1889 |isbn=978-0-309-04631-2 |language=en}}</ref> It's also an important part of the ozone layer, which can be found in different sections of the stratosphere. Photochemical and chemical reactions involving it fuel many of the chemical activities that occur in the atmosphere during the day and night. It is a pollutant and a component of [[Earth:Smog|smog]] that is produced in large quantities as a result of human activities (mostly the combustion of fossil fuels).<ref>{{Cite web |title=ESS Topic 6.3: Photochemical Smog |url=https://www.mrgscience.com/ess-topic-63-photochemical-smog.html |access-date=2022-06-07 |website=Amazing World of Science With Mr. Green |language=en}}</ref>
* [[Chemistry:Peroxyacetyl nitrate|Peroxyacetyl nitrate]] (C<sub>2</sub>H<sub>3</sub>NO<sub>5</sub>): similarly formed from NO<sub>x</sub> and VOCs.
* Photochemical smog: particles are formed from gaseous primary contaminants and chemicals.<ref>{{Citation |last=Acharya |first=Bishnu |title=Chapter 10 - Cleaning of Product Gas of Gasification |date=2018-01-01 |url=https://www.sciencedirect.com/science/article/pii/B9780128129920000108 |work=Biomass Gasification, Pyrolysis and Torrefaction (Third Edition) |pages=373–391 |editor-last=Basu |editor-first=Prabir |publisher=Academic Press |language=en |isbn=978-0-12-812992-0 |access-date=2022-06-07}}</ref> Smog is a type of pollution that occurs in the atmosphere. Smog is caused by a huge volume of coal being burned in a certain region, resulting in a mixture of smoke and sulfur dioxide.<ref>{{Cite web |title=smog {{!}} National Geographic Society |url=https://education.nationalgeographic.org/resource/smog/ |access-date=2022-06-07 |website=education.nationalgeographic.org |publisher=National Geographic}}</ref> Modern smog is usually caused by automotive and industrial emissions, which are acted on in the atmosphere by UV light from the sun to produce secondary pollutants, which then combine with the primary emissions to generate photochemical smog.

===Other pollutants===

There are many other chemicals classed as hazardous air pollutants. Some of these are regulated in the USA under the Clean Air Act and in Europe under numerous directives (including the Air "Framework" Directive, 96/62/EC, on ambient air quality assessment and management, Directive 98/24/EC, on risks related to chemical agents at work, and Directive 2004/107/EC covering heavy metals and polycyclic aromatic hydrocarbons in ambient air).<ref>{{cite web |title=Hazardous Air Pollutants |url=https://www.epa.gov/haps |website=US Environmental Protection Agency |access-date=29 April 2023 |date=9 February 2023}}</ref><ref>{{cite web |title=Air quality standards |url=https://www.eea.europa.eu/themes/air/air-quality-concentrations/air-quality-standards |website=European Environment Agency |access-date=29 April 2023}}</ref>

{{category tree all|Hazardous air pollutants|mode=all|depth=0}}
<gallery widths="200px" heights="160px">
File:Air pollution by industrial chimneys.jpg|Before [[Physics:Flue-gas desulfurization|flue-gas desulfurization]] was installed, the emissions from this power plant in New Mexico contained excessive amounts of [[Chemistry:Sulfur dioxide|sulfur dioxide]].
File:Thermal-oxidizer-rto.jpg|Thermal oxidisers are air pollution abatement options for hazardous air pollutants (HAPs), volatile organic compounds (VOCs), and odorous emissions.
File:NASA - Human Fingerprint on Global Air Quality.webm|This video provides an overview of a NASA study on the human fingerprint on global air quality.
</gallery>

== Exposure ==
[[File:Air pollution exposure in cities - EU limits vs WHO guidelines.svg|thumb|In 2012, up to 30% of Europeans living in cities are exposed to air pollutant levels exceeding EU air quality standards. Around 98% of Europeans living in cities are exposed to levels of air pollutants deemed damaging to health by the World Health Organization's more stringent guidelines.<ref>{{Cite web|url=https://www.eea.europa.eu/media/infographics/air-pollution-exposure-in-cities/view |title=Air pollution exposure in cities |website=European Environment Agency |access-date=9 March 2019}}</ref>]]

The risk of air pollution is determined by the pollutant's hazard and the amount of exposure to that pollutant. Air pollution exposure can be measured for a person, a group, such as a neighborhood or a country's children, or an entire population. For example, one would want to determine a geographic area's exposure to a dangerous air pollution, taking into account the various microenvironments and age groups. This can be calculated<ref name="Daniel A. Vallero">{{cite web|title=Fundamentals of Air Pollution|author=Daniel A. Vallero|publisher=Elsevier Academic Press|url=http://store.elsevier.com/Fundamentals-of-Air-Pollution/Daniel-Vallero/isbn-9780123736154/}}</ref> as an inhalation exposure. This would account for daily exposure in various settings, e.g. different indoor micro-environments and outdoor locations. The exposure needs to include different ages and other demographic groups, especially infants, children, pregnant women, and other sensitive subpopulations.<ref name="Daniel A. Vallero"/>

For each specific time that the subgroup is in the setting and engaged in particular activities, the exposure to an air pollutant must integrate the concentrations of the air pollutant with regard to the time spent in each setting and the respective inhalation rates for each subgroup, playing, cooking, reading, working, spending time in traffic, etc. A little child's inhaling rate, for example, will be lower than that of an adult. A young person engaging in strenuous exercise will have a faster rate of breathing than a child engaged in sedentary activity. The daily exposure must therefore include the amount of time spent in each micro-environmental setting as well as the kind of activities performed there. The air pollutant concentration in each microactivity/microenvironmental setting is summed to indicate the exposure.<ref name="Daniel A. Vallero"/>

For some pollutants such as [[Earth:Black carbon|black carbon]], traffic related exposures may dominate total exposure despite short exposure times since high concentrations coincide with proximity to major roads or participation in (motorized) traffic.<ref name="Dons et al.">{{cite journal|last=Dons |first=E. |title=Impact of time-activity patterns on personal exposure to black carbon |journal=[[Earth:Atmospheric Environment|Atmospheric Environment]] |volume=45 |issue=21 |pages=3594–3602 |year=2011 |doi=10.1016/j.atmosenv.2011.03.064 |bibcode=2011AtmEn..45.3594D}}</ref> A large portion of total daily exposure occurs as short peaks of high concentrations, but it remains unclear how to define peaks and determine their frequency and health impact.<ref name="Dons et al. 2019">{{cite journal |last=Dons |first=E. |title=Transport most likely to cause air pollution peak exposures in everyday life: Evidence from over 2000 days of personal monitoring |journal=[[Earth:Atmospheric Environment|Atmospheric Environment]] |volume=213 |pages=424–432 |year=2019 |doi=10.1016/j.atmosenv.2019.06.035 |bibcode=2019AtmEn.213..424D |hdl=10044/1/80194 |s2cid=197131423 |hdl-access=free}}</ref>

In 2021, the WHO halved its recommended guideline limit for tiny particles from burning fossil fuels. The new limit for [[Chemistry:Nitrogen dioxide|nitrogen dioxide]] (NO<sub>2</sub>) is 75% lower.<ref>{{Cite web|last=Carrington |first=Damian |date=2021-09-22 |title=WHO slashes guideline limits on air pollution from fossil fuels |url=https://www.theguardian.com/environment/2021/sep/22/who-cuts-guideline-limits-on-air-pollution-from-fossil-fuels |access-date=2021-09-22 |website={{wipe|The Guardian}} |language=en}}</ref> Growing evidence that air pollution—even when experienced at very low levels—hurts human health, led the WHO to revise its guideline (from 10&nbsp;µg/m³ to 5&nbsp;µg/m³) for what it considers a safe level of exposure of particulate pollution, bringing most of the world—97.3 percent of the global population—into the unsafe zone.<ref>{{Cite web |date=2022-06-14 |title=Most of the World Breathes Unsafe Air, Taking More Than 2 Years Off Global Life Expectancy |url=https://aqli.epic.uchicago.edu/news/most-of-the-world-breathes-unsafe-air-taking-more-than-2-years-off-global-life-expectancy/ |access-date=2022-07-12 |website=AQLI |language=en}}</ref>

== Indoor air quality ==
[[File:Share of deaths from indoor air pollution, OWID.svg|thumb|upright=1.5|The share of total deaths from indoor air pollution, 2017]]
[[File:New Delhi Met Office, India 02.jpg|thumb|Air quality monitoring, New Delhi, India]]

A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time. [[Chemistry:Radon|Radon]] (Rn) gas, a [[Biology:Carcinogen|carcinogen]], is exuded from the Earth in certain locations and trapped inside houses. Building materials including carpeting and [[Chemistry:Plywood|plywood]] emit [[Physics:Formaldehyde|formaldehyde]] (H-CHO) gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry. [[Chemistry:Lead|Lead]] paint can degenerate into dust and be inhaled.<ref name="sapiens.revues.org">{{cite journal|url=http://sapiens.revues.org/index130.html |title=Indoor air pollution, health and economic well-being |journal=S.A.P.I.EN.S |volume=1 |issue=1 |date=26 November 2008|access-date=29 August 2010 |last1=Duflo |first1=Esther |last2=Greenstone |first2=Michael |last3=Hanna |first3=Rema}}</ref><ref name="Improved Clean Cookstoves">{{Cite web|date=7 February 2020 |title=Improved Clean Cookstoves |url=https://www.drawdown.org/solutions/improved-clean-cookstoves |access-date=5 December 2020 |website=Project Drawdown |language=en}}</ref>

Intentional air pollution is introduced with the use of air fresheners, incense, and other scented items. Controlled wood fires in cook stoves and fireplaces can add significant amounts of harmful smoke particulates into the air, inside and out.<ref name="sapiens.revues.org"/><ref name="Improved Clean Cookstoves"/> Indoor pollution fatalities may be caused by using [[Biology:Pesticide|pesticide]]s and other chemical sprays indoors without proper ventilation. Also the kitchen in a modern produce harmful particles and gases, with equipment like toasters being one of the worst sources.<ref>{{Cite magazine|url=https://www.newyorker.com/magazine/2019/04/08/the-hidden-air-pollution-in-our-homes|title=The Hidden Air Pollution in Our Homes|first=Nicola|last=Twilley|magazine=The New Yorker |date=1 April 2019|via=www.newyorker.com}}</ref>

Carbon monoxide poisoning and fatalities are often caused by faulty vents and chimneys, or by the burning of charcoal indoors or in a confined space, such as a tent.<ref>{{cite news|title=Bucknell tent death: Hannah Thomas-Jones died from carbon monoxide poisoning |url=https://www.bbc.co.uk/news/uk-england-21059594 |access-date=22 September 2015 |work=BBC News |date=17 January 2013}}</ref> Chronic [[Medicine:Carbon monoxide poisoning|carbon monoxide poisoning]] can result even from poorly-adjusted [[Engineering:Pilot light|pilot light]]s. Traps are built into all domestic [[Engineering:Plumbing|plumbing]] to keep sewer gas and [[Chemistry:Hydrogen sulfide|hydrogen sulfide]], out of interiors. Clothing emits [[Chemistry:Tetrachloroethylene|tetrachloroethylene]], or other dry cleaning fluids, for days after dry cleaning.

Though its use has now been banned in many countries, the extensive use of [[Chemistry:Asbestos|asbestos]] in industrial and domestic environments in the past has left a potentially very dangerous material in many localities. [[Medicine:Asbestosis|Asbestosis]] is a chronic [[Medicine:Inflammation|inflammatory]] medical condition affecting the tissue of the lungs. It occurs after long-term, heavy exposure to asbestos from asbestos-containing materials in structures. Those with asbestosis have severe dyspnea (shortness of breath) and are at an increased risk regarding several different types of lung cancer. As clear explanations are not always stressed in non-technical literature, care should be taken to distinguish between several forms of relevant diseases. According to the World Health Organization,<ref>{{Cite web |title=Chapter 6.2. Asbestos. Air quality guidelines, Second edition. |url=http://www.euro.who.int/__data/assets/pdf_file/0015/123072/AQG2ndEd_6_2_asbestos.PDF |url-status=dead |archive-url=https://web.archive.org/web/20110524203454/http://www.euro.who.int/__data/assets/pdf_file/0015/123072/AQG2ndEd_6_2_asbestos.PDF |archive-date=2011-05-24 |website=[[Organization:World Health Organization|World Health Organization]] Europe}}</ref> these may be defined as asbestosis, lung cancer, and peritoneal mesothelioma (generally a very rare form of cancer, when more widespread it is almost always associated with prolonged exposure to asbestos).

Biological sources of air pollution are also found indoors, as gases and airborne particulates. Pets produce dander, people produce dust from minute skin flakes and decomposed hair, [[Biology:House dust mite|dust mites]] in bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane, mold forms on walls and generates mycotoxins and spores, [[Physics:Air conditioning|air conditioning]] systems can incubate Legionnaires' disease and mold, and houseplants, soil and surrounding gardens can produce [[Biology:Pollen|pollen]], dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature.

== Health effects ==
Even at levels lower than those considered safe by United States regulators, exposure to three components of air pollution, fine particulate matter, nitrogen dioxide and ozone, correlates with cardiac and respiratory illness.<ref>{{cite web|website=Science Daily |date=22 February 2021 |url=https://www.sciencedaily.com/releases/2021/02/210222082622.htm |title=Long-Term Exposure to Low Levels of Air Pollution Increases Risk of Heart and Lung Disease}}</ref> In 2020, pollution (including air pollution) was a contributing factor to one in eight deaths in Europe, and was a significant risk factor for pollution-related diseases including heart disease, [[Medicine:Stroke|stroke]] and lung cancer.<ref>{{cite news |title=EU says one in eight deaths is linked to pollution |url=https://www.bbc.com/news/world-europe-54071380 |access-date=16 September 2021 |work=BBC News |date=8 September 202}}</ref> The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing, [[Medicine:Asthma|asthma]]<ref name=":1">{{Cite news|last=Carrington |first=Damian |date=2021-05-18 |title=Air pollution linked to 'huge' rise in child asthma GP visits |url=http://www.theguardian.com/environment/2021/may/18/air-pollution-linked-to-huge-rise-in-child-asthma-gp-visits |access-date=2021-05-22 |work={{wipe|The Guardian}} |language=en}}</ref> and worsening of existing respiratory and cardiac conditions. These effects can result in increased medication use, increased doctor or [[Medicine:Emergency department|emergency department]] visits, more hospital admissions and premature death.<ref name="Daniel A. Vallero"/>

The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, and the individual's health status and genetics.<ref name="Daniel A. Vallero"/> The most common sources of air pollution include particulates, ozone, nitrogen dioxide, and sulfur dioxide. Children aged less than five years who live in developing countries are the most vulnerable population in terms of total deaths attributable to indoor and outdoor air pollution.<ref>{{cite web |url=https://www.who.int/mediacentre/factsheets/fs313/en/index.html |title=Air quality and health |website=Who.int |publisher=[[Organization:World Health Organization|World Health Organization]] |access-date=26 November 2011}}</ref> Under the Clean Air Act, U.S. EPA sets limits on certain air pollutants, including setting limits on how much can be in the air anywhere in the United States.<ref>{{Cite web |last=US EPA |first=OMS |date=2013-02-22 |title=Regulatory and Guidance Information by Topic: Air |url=https://www.epa.gov/regulatory-information-topic/regulatory-and-guidance-information-topic-air |access-date=2022-11-10 |website=www.epa.gov |language=en}}</ref> New research demonstrates that the biological and health outcomes of mixed exposures (Example&nbsp;PM + Ozone) could be significantly greater than individual exposures.<ref>{{Cite journal |journal=Toxicological Sciences |doi=10.1093/toxsci/kfac113|title=Aerosol physicochemical determinants of carbon black and ozone inhalation co-exposure induced pulmonary toxicity |year=2022 |last1=Majumder |first1=Nairrita |last2=Kodali |first2=Vamsi |last3=Velayutham |first3=Murugesan |last4=Goldsmith |first4=Travis |last5=Amedro |first5=Jessica |last6=Khramtsov |first6=Valery V. |last7=Erdely |first7=Aaron |last8=Nurkiewicz |first8=Timothy R. |last9=Harkema |first9=Jack R. |last10=Kelley |first10=Eric E. |last11=Hussain |first11=Salik |volume=191 |issue=1 |pages=61–78 |pmid=36303316 |pmc=9887725 }}</ref>

Air pollution has both acute and chronic effects on human health, affecting a number of different systems and organs. It ranges from minor upper respiratory irritation to chronic respiratory and heart disease, lung cancer, acute respiratory infections in children and chronic bronchitis in adults, aggravating pre-existing heart and lung disease, or asthmatic attacks. Short and long term exposures have been linked with premature mortality and reduced life expectancy.<ref>{{Cite journal |last1=Kampa |first1=Marilena |last2=Castanas |first2=Elias |date=2008-01-01 |title=Human health effects of air pollution |url=https://www.sciencedirect.com/science/article/pii/S0269749107002849 |journal=Environmental Pollution |series=Proceedings of the 4th International Workshop on Biomonitoring of Atmospheric Pollution (With Emphasis on Trace Elements) |language=en |volume=151 |issue=2 |pages=362–367 |doi=10.1016/j.envpol.2007.06.012 |pmid=17646040 |s2cid=38513536 |issn=0269-7491}}</ref> Diseases that develop from persistent exposure to air pollution are [[Earth:Environmental health|environmental health]] diseases, which develop when a health environment is not maintained.<ref>{{cite book | last1=Dovjak | first1=Mateja | last2=Kukec | first2=Andreja | title=Creating Healthy and Sustainable Buildings | chapter=Health Outcomes Related to Built Environments | publisher=Springer International Publishing | publication-place=Switzerland | year=2019 | isbn=978-3-030-19411-6 | doi=10.1007/978-3-030-19412-3_2 | oclc=1285508857 | pages = 43–82| s2cid=190160283 }}</ref>

=== Mortality ===
[[File:How-many-people-die-from-air-pollution-1-1.png|thumb|upright=1.85]]
{{ multiple image |total_width=450
| image1= 2021 Death rates, by energy source.svg |caption1= Deaths caused by accidents and air pollution from fossil fuel use in power plants exceed those caused by production of [[Engineering:Renewable energy|renewable energy]].<ref name=OWID_SafestEnergy_2021>{{cite journal |last1=Ritchie |first1=Hannah |last2=Roser |first2=Max |title=What are the safest and cleanest sources of energy? |url=https://ourworldindata.org/safest-sources-of-energy |journal=Our World in Data |archive-url=https://web.archive.org/web/20240115112316/https://ourworldindata.org/safest-sources-of-energy |archive-date=15 January 2024 |date=2021 |url-status=live }} Data sources: Markandya & Wilkinson (2007); UNSCEAR (2008; 2018); Sovacool et al. (2016); IPCC AR5 (2014); Pehl et al. (2017); Ember Energy (2021).</ref>
| image2= Share of deaths from outdoor air pollution, OWID.svg |caption2=The share of total deaths from outdoor air pollution, by nation
}}

The World Health Organization estimated in 2014 that every year air pollution causes the premature death of some 7 million people worldwide.<ref name="WHO2014"/> Studies published in March 2019 indicated that the number may be around 8.8 million.<ref name="2019-03-12-guardian"/> A 2022 review concluded that air pollution was responsible for 6.67 (5.90–7.49) million premature deaths in 2019. It concluded that since 2015 little real progress against (superordinate) pollution, which remained at ~9 million earlier deaths, can be identified.<ref>{{cite news |last1=Dickie |first1=Gloria |title=Pollution killing 9 million people a year, Africa hardest hit - study |url=https://www.reuters.com/business/environment/pollution-killing-9-million-people-year-africa-hardest-hit-study-2022-05-17/ |access-date=23 June 2022 |work={{wipe|Reuters}} |date=18 May 2022 |language=en}}</ref><ref name="10.1016/S2542-5196(22)00090-0">{{cite journal |last1=Fuller |first1=Richard |last2=Landrigan |first2=Philip J |last3=Balakrishnan |first3=Kalpana |last4=Bathan |first4=Glynda |last5=Bose-O'Reilly |first5=Stephan |last6=Brauer |first6=Michael |last7=Caravanos |first7=Jack |last8=Chiles |first8=Tom |last9=Cohen |first9=Aaron |last10=Corra |first10=Lilian |last11=Cropper |first11=Maureen |last12=Ferraro |first12=Greg |last13=Hanna |first13=Jill |last14=Hanrahan |first14=David |last15=Hu |first15=Howard |last16=Hunter |first16=David |last17=Janata |first17=Gloria |last18=Kupka |first18=Rachael |last19=Lanphear |first19=Bruce |last20=Lichtveld |first20=Maureen |last21=Martin |first21=Keith |last22=Mustapha |first22=Adetoun |last23=Sanchez-Triana |first23=Ernesto |last24=Sandilya |first24=Karti |last25=Schaefli |first25=Laura |last26=Shaw |first26=Joseph |last27=Seddon |first27=Jessica |last28=Suk |first28=William |last29=Téllez-Rojo |first29=Martha María |last30=Yan |first30=Chonghuai |title=Pollution and health: a progress update |journal=The Lancet Planetary Health |date=June 2022 |volume=6 |issue=6 |pages=e535–e547 |doi=10.1016/S2542-5196(22)00090-0|pmid=35594895 |s2cid=248905224}}</ref>
Causes of deaths include strokes, heart disease, COPD, lung cancer, and lung infections.<ref name="WHO2014"/>

Urban outdoor air pollution is estimated to cause 1.3 million deaths worldwide per year.<ref>{{cite journal |last1=Huang |first1=Yuh-Chin T. |title=Outdoor air pollution: a global perspective |journal=Journal of Occupational and Environmental Medicine |date=October 2014 |volume=56 |issue=Suppl 10 |pages=S3–7 |doi=10.1097/JOM.0000000000000240 |pmid=25285972 |issn=1536-5948}}</ref> Children are particularly at risk due to the immaturity of their respiratory organ systems.<ref>{{Cite web |url=https://www.who.int/ceh/risks/cehair/en/|title=Air pollution |website=[[Organization:World Health Organization|World Health Organization]] |access-date=2 December 2016}}</ref> In 2015, outdoor air pollution, mostly by PM<sub>2.5</sub>, was estimated to lead to 3.3 (95% CI 1.61–4.81) million premature deaths per year worldwide, predominantly in Asia.<ref name="10.1038/nature15371"/> In 2021, the WHO reported that outdoor air pollution was estimated to cause 4.2 million premature deaths worldwide in 2016.<ref name="who2021">{{cite news |title=Ambient (outdoor) air pollution |url=https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health |access-date=20 December 2021 |work=www.who.int |publisher=[[Organization:World Health Organization|World Health Organization]] |language=en}}</ref>

A 2020 study indicates that the global mean loss of life expectancy (LLE; similar to [[Years of potential life lost|YPLL]]) from air pollution in 2015 was 2.9 years, substantially more than, for example, 0.3 years from all forms of direct violence, albeit a significant fraction of the LLE is unavoidable.<ref name="10.1093/cvr/cvaa025">{{cite journal |last1=Lelieveld |first1=Jos |last2=Pozzer |first2=Andrea |last3=Pöschl |first3=Ulrich |last4=Fnais |first4=Mohammed |last5=Haines |first5=Andy |last6=Münzel |first6=Thomas |title=Loss of life expectancy from air pollution compared to other risk factors: a worldwide perspective |journal=Cardiovascular Research |date=1 September 2020 |volume=116 |issue=11 |pages=1910–1917 |doi=10.1093/cvr/cvaa025 |pmid=32123898 |pmc=7449554 |issn=0008-6363}}</ref> Communities with the most exceptional aging have low ambient air pollution, suggesting a link between air pollution levels and longevity.<ref>{{cite journal |last1=Baccarelli |first1=Andrea A. |last2=Hales |first2=Nick |last3=Burnett |first3=Richard T. |last4=Jerrett |first4=Michael |last5=Mix |first5=Carter |last6=Dockery |first6=Douglas W. |last7=Pope |first7=C. Arden |title=Particulate Air Pollution, Exceptional Aging, and Rates of Centenarians: A Nationwide Analysis of the United States, 1980–2010 |journal=Environmental Health Perspectives |date=1 November 2016 |volume=124 |issue=11 |pages=1744–1750 |doi=10.1289/EHP197|pmid=27138440 |pmc=5089884}}</ref>

A study published in 2022 in ''[[Organization:American Geophysical Union#Publications|GeoHealth]]'' concluded that eliminating energy-related fossil fuel emissions in the United States would prevent 46,900–59,400 premature deaths each year and provide $537–$678 billion in benefits from avoided PM<sub>2.5</sub>-related illness and death.<ref name=GeoHealth_20220516>{{cite journal |last1=Mailloux |first1=Nicholas A. |last2=Abel |first2=David W. |last3=Holloway |first3=Tracey |last4=Patz |first4=Jonathan A. |title=Nationwide and Regional PM2.5-Related Air Quality Health Benefits From the Removal of Energy-Related Emissions in the United States |journal=GeoHealth |volume=6 |issue=5 |date=16 May 2022 |pages=e2022GH000603 |doi=10.1029/2022GH000603 |pmid=35599962 |pmc=9109601}}</ref>

==== By region ====
India and China have the highest death rate due to air pollution.<ref>{{Cite news |last=Harris |first=Gardiner |date=2014-01-25 |title=Beijing's Bad Air Would Be Step Up for Smoggy Delhi |language=en-US |work=The New York Times |url=https://www.nytimes.com/2014/01/26/world/asia/beijings-air-would-be-step-up-for-smoggy-delhi.html |access-date=2023-04-28 |issn=0362-4331}}</ref><ref>{{Cite journal|last1=Owusu |first1=Phebe Asantewaa |last2=Sarkodie |first2=Samuel Asumadu |date=2020-11-10 |title=Global estimation of mortality, disability-adjusted life years and welfare cost from exposure to ambient air pollution |url=https://www.sciencedirect.com/science/article/pii/S0048969720341589 |journal=Science of the Total Environment |language=en |volume=742 |pages=140636 |doi=10.1016/j.scitotenv.2020.140636 |pmid=32721745 |bibcode=2020ScTEn.742n0636O |s2cid=220848545 |issn=0048-9697}}</ref> India also has more deaths from asthma than any other nation according to the World Health Organization. In 2019, 1.6 million deaths in India were caused by air pollution.<ref>{{Cite news |date=2022-05-18 |title=Lancet study: Pollution killed 2.3 million Indians in 2019 |language=en-GB |work=BBC News |url=https://www.bbc.com/news/world-asia-india-61489488 |access-date=2023-04-28}}</ref> In December 2013, air pollution was estimated to kill 500,000 people in China each year.<ref>Mr Chen's claim was made in The Lancet (December 2013 issue) and reported in The Daily Telegraph 8 January 2014 p. 15 'Air pollution killing up to 500,000 Chinese each year, admits former health minister.</ref> There is a positive correlation between [[Medicine:Pneumonia|pneumonia]]-related deaths and air pollution from motor vehicle emissions.<ref>{{cite news |title=Study links traffic pollution to thousands of deaths |url=https://www.theguardian.com/society/2008/apr/15/health |work={{wipe|The Guardian}} |location=London, UK |date=15 April 2008 |access-date=15 April 2008 |archive-url=https://web.archive.org/web/20080420100121/http://www.guardian.co.uk/society/2008/apr/15/health |archive-date=20 April 2008 |url-status=live}}</ref>

Annual premature European deaths caused by air pollution are estimated at 430,000<ref name="europarl.europa.eu">{{cite web|url=http://www.europarl.europa.eu/news/en/news-room/20160222STO15305/Car-emissions-taking-tests-out-of-the-lab-and-onto-the-road |title=Car emissions: taking tests out of the lab and onto the road – News |publisher=European Parliament |access-date=11 January 2018 |date=25 February 2016}}</ref> to 800,000.<ref name="2019-03-12-guardian">{{cite news|last=Carrington |first=Damian |date=12 March 2019 |title=Air pollution deaths are double previous estimates, finds research |url=https://www.theguardian.com/environment/2019/mar/12/air-pollution-deaths-are-double-previous-estimates-finds-research |access-date=12 March 2019 |work={{wipe|The Guardian}}}}</ref> An important cause of these deaths is nitrogen dioxide and other nitrogen oxides (NOx) emitted by road vehicles.<ref name="europarl.europa.eu"/> In a 2015 consultation document the UK government disclosed that nitrogen dioxide is responsible for 23,500 premature UK deaths per annum.<ref>{{Cite web|url=https://motorway.co.uk/guides/diesel-car-toxin-tax |title=Complete Guide To The 'Toxin Tax' For Diesel Cars |website=Motorway |access-date=25 May 2017}}</ref> Across the [[Social:European Union|European Union]], air pollution is estimated to reduce [[Biology:Life expectancy|life expectancy]] by almost nine months.<ref>{{cite news |url=http://news.bbc.co.uk/2/hi/health/4283295.stm |title=Air pollution causes early deaths |publisher=BBC |date=21 February 2005 |access-date=14 August 2012}}</ref>

==== Guidelines ====
{{Main|Earth:Air quality guideline}}
The US EPA has estimated that limiting ground-level ozone concentration to 65 parts per billion (ppb), would avert 1,700 to 5,100 premature deaths nationwide in 2020 compared with the 75&nbsp;ppb standard. The agency projected the more protective standard would also prevent an additional 26,000 cases of aggravated asthma, and more than a million cases of missed work or school.<ref>{{cite news | url=http://articles.latimes.com/2010/jan/08/nation/la-na-epa-smog-rules8-2010jan08 |title=EPA proposes nation's strictest smog limits ever |work={{wipe|Los Angeles Times}} |date=8 January 2010 |access-date=14 August 2012 |last=Tankersley |first=Jim}}</ref><ref>{{cite web |url=http://yosemite.epa.gov/sab/sabproduct.nsf/0E6B12C5232316558525783400611BE6/$File/ALA+slides.pdf |title=EPA slideshow |access-date=11 December 2012}}</ref> Following this assessment, the EPA acted to protect public health by lowering the National Ambient Air Quality Standards (NAAQS) for ground-level ozone to 70&nbsp;ppb.<ref>{{cite web|url=https://yosemite.epa.gov/opa/admpress.nsf/931381dfcd9a5c308525779700424ccd/ffe8a2d2a59797b385257ed000724bf0!OpenDocument |title=EPA Strengthens Ozone Standards to Protect Public Health/Science-based standards to reduce sick days, asthma attacks, emergency room visits, greatly outweigh costs (10/1/2015) |website=Yosemite.epa.gov |access-date=11 January 2018}}</ref>

A 2008 economic study of the health impacts and associated costs of air pollution in the Los Angeles Basin and San Joaquin Valley of Southern California shows that more than 3,800 people die prematurely (approximately 14 years earlier than normal) each year because air pollution levels violate federal standards. The number of annual premature deaths is considerably higher than the fatalities related to auto collisions in the same area, which average fewer than 2,000 per year.<ref>{{cite web |url=http://www.sacbee.com/378/story/1393268.html | archive-url=https://web.archive.org/web/20081216071959/http://www.sacbee.com/378/story/1393268.html |archive-date=16 December 2008 |title=Human cost of valley's dirty air: $6.3 billion |publisher=Sacramento Bee |date=13 November 2008 |access-date=14 August 2012 |last=Grossni |first=Mark}}</ref><ref>{{cite news |url=http://articles.latimes.com/2008/nov/13/local/me-pollute13 |title=Pollution saps state's economy, study says |work={{wipe|Los Angeles Times}} |date=13 November 2008 |access-date=14 August 2012 |last=Sahagun |first=Louis}}</ref><ref>{{cite news |url=http://www.sfgate.com/health/article/Bad-air-costing-state-s-economy-billions-3185388.php |title=Bad air costing state's economy billions |publisher=San Francisco Chronicle |date=13 November 2008 |access-date=14 August 2012 |last=Kay |first=Jane}}</ref> A 2021 study found that outdoor air pollution is associated with substantially [[Social:List of causes of death by rate#Air pollution|increased mortality]] "even at low pollution levels below the current European and North American standards and WHO guideline values" shortly before the WHO adjusted its guidelines.<ref>{{cite news |title=Human health may be at risk from long-term exposure to air pollution below current air quality standards and guidelines |url=https://medicalxpress.com/news/2021-09-human-health-long-term-exposure-air.html |access-date=18 October 2021 |work=British Medical Journal |language=en}}</ref><ref>{{cite journal |last1=Strak |first1=Maciej |last2=Weinmayr |first2=Gudrun |last3=Rodopoulou |first3=Sophia |last4=Chen |first4=Jie |last5=Hoogh |first5=Kees de |last6=Andersen |first6=Zorana J. |last7=Atkinson |first7=Richard |last8=Bauwelinck |first8=Mariska |last9=Bekkevold |first9=Terese |last10=Bellander |first10=Tom |last11=Boutron-Ruault |first11=Marie-Christine |last12=Brandt |first12=Jørgen |last13=Cesaroni |first13=Giulia |last14=Concin |first14=Hans |last15=Fecht |first15=Daniela |last16=Forastiere |first16=Francesco |last17=Gulliver |first17=John |last18=Hertel |first18=Ole |last19=Hoffmann |first19=Barbara |last20=Hvidtfeldt |first20=Ulla Arthur |last21=Janssen |first21=Nicole A. H. |last22=Jöckel |first22=Karl-Heinz |last23=Jørgensen |first23=Jeanette T. |last24=Ketzel |first24=Matthias |last25=Klompmaker |first25=Jochem O. |last26=Lager |first26=Anton |last27=Leander |first27=Karin |last28=Liu |first28=Shuo |last29=Ljungman |first29=Petter |last30=Magnusson |first30=Patrik K. E. |last31=Mehta |first31=Amar J. |last32=Nagel |first32=Gabriele |last33=Oftedal |first33=Bente |last34=Pershagen |first34=Göran |last35=Peters |first35=Annette |last36=Raaschou-Nielsen |first36=Ole |last37=Renzi |first37=Matteo |last38=Rizzuto |first38=Debora |last39=Schouw |first39=Yvonne T. van der |last40=Schramm |first40=Sara |last41=Severi |first41=Gianluca |last42=Sigsgaard |first42=Torben |last43=Sørensen |first43=Mette |last44=Stafoggia |first44=Massimo |last45=Tjønneland |first45=Anne |last46=Verschuren |first46=W. M. Monique |last47=Vienneau |first47=Danielle |last48=Wolf |first48=Kathrin |last49=Katsouyanni |first49=Klea |last50=Brunekreef |first50=Bert |last51=Hoek |first51=Gerard |last52=Samoli |first52=Evangelia |title=Long term exposure to low level air pollution and mortality in eight European cohorts within the ELAPSE project: pooled analysis |journal=BMJ |date=2 September 2021 |volume=374 |pages=n1904 |doi=10.1136/bmj.n1904 |pmid=34470785 |pmc=8409282 |language=en |issn=1756-1833}}</ref>

==== Major causes ====
[[File:Comparison of footprint-based and transboundary pollution-based relationships among G20 nations for the number of PM2.5-related premature deaths.webp|thumb|300px|A comparison of footprint-based and transboundary pollution-based relationships among G20 nations for the number of PM<sub>2.5</sub>-related premature deaths<ref name="10.1038/s41467-021-26348-y"/>]]
The largest cause is air pollution generated by fossil fuel combustion<ref name="10.1016/j.envres.2021.110754"/>&nbsp;– mostly the production and use of [[Engineering:Car|car]]s, electricity production, and heating.<ref>{{Cite web |date=June 22, 2021 |last1=Mackenzie |first1=Jillian |last2=Turrentine |first2=Jeff |title=Air Pollution: Everything You Need to Know |url=https://www.nrdc.org/stories/air-pollution-everything-you-need-know |access-date=2022-06-18 |website=NRDC |language=en}}</ref><!--https://ourworldindata.org/fossil-fuels--> A study by Greenpeace estimates there are 4.5 million annual premature deaths worldwide because of pollutants released by high-emission power stations and vehicle exhausts.<ref>{{Cite web|title=Air pollution causing 65,000 annual deaths in Middle East, report finds |url=https://www.thenational.ae/uae/science/air-pollution-causing-65-000-annual-deaths-in-middle-east-report-finds-1.1053843 |access-date=24 July 2020 |website=The National |date=24 July 2020 |language=en}}</ref>

[[Earth:Diesel exhaust|Diesel exhaust]] (DE) is a major contributor to combustion-derived particulate matter air pollution. In several human experimental studies, using a well-validated exposure chamber setup, DE has been linked to acute vascular dysfunction and increased thrombus formation.<ref>{{Cite journal |last1=Lucking |first1=A. J. |last2=Lundback |first2=M. |last3=Mills |first3=N. L. |last4=Faratian |first4=D. |last5=Barath |first5=S. L. |last6=Pourazar |first6=J. |last7=Cassee |first7=F. R. |last8=Donaldson |first8=K. |last9=Boon |first9=N. A. |last10=Badimon |first10=J. J. |last11=Sandstrom |first11=T. |last12=Blomberg |first12=A. |last13=Newby |first13= D. E. |title=Diesel exhaust inhalation increases thrombus formation in man |doi=10.1093/eurheartj/ehn464 |journal=European Heart Journal |volume=29 |issue=24 |pages=3043–51 |year=2008 |pmid=18952612 |doi-access=free}}</ref><ref>{{Cite journal |last1=Törnqvist |first1=H. K. |last2=Mills |first2=N. L. |last3=Gonzalez |first3=M. |last4=Miller |first4=M. R. |last5=Robinson |first5=S. D. |last6=Megson | first6=I. L. |last7=MacNee | first7=W. |last8=Donaldson | first8=K. |last9=Söderberg | first9=S. |last10=Newby |first10=D. E. |last11=Sandström |first11=T. |last12=Blomberg |first12=A. |doi=10.1164/rccm.200606-872OC |title=Persistent Endothelial Dysfunction in Humans after Diesel Exhaust Inhalation |journal=American Journal of Respiratory and Critical Care Medicine |volume=176 |issue=4 |pages=395–400 |year=2007 |pmid=17446340}}</ref>

A study concluded that PM<sub>2.5</sub> air pollution [[Earth:Embedded emissions|induced]] by the contemporary free trade and consumption by the {{tooltip|2=the EU as a whole (not a nation) is not included here|19}} G20 nations causes two million premature deaths annually, suggesting that the average lifetime consumption of about ~28 people in these countries causes at least one premature death (average age ~67) while developing countries "cannot be expected" to implement or be able to implement countermeasures without external support or internationally coordinated efforts.<ref>{{cite news |title=Air pollution from G20 consumers caused two million deaths in 2010 |url=https://www.newscientist.com/article/2295873-air-pollution-from-g20-consumers-caused-two-million-deaths-in-2010/ |access-date=11 December 2021 |work=New Scientist}}</ref><ref name="10.1038/s41467-021-26348-y">{{cite journal |last1=Nansai |first1=Keisuke |last2=Tohno |first2=Susumu |last3=Chatani |first3=Satoru |last4=Kanemoto |first4=Keiichiro |last5=Kagawa |first5=Shigemi |last6=Kondo |first6=Yasushi |last7=Takayanagi |first7=Wataru |last8=Lenzen |first8=Manfred |title=Consumption in the G20 nations causes particulate air pollution resulting in two million premature deaths annually |journal=Nature Communications |date=2 November 2021 |volume=12 |issue=1 |pages=6286 |doi=10.1038/s41467-021-26348-y |pmid=34728619 |pmc=8563796 |bibcode=2021NatCo..12.6286N |language=en |issn=2041-1723}}</ref>

==== Primary mechanisms ====
The WHO estimates that in 2016, ~58% of outdoor air pollution-related premature deaths were due to ischaemic heart disease and stroke.<ref name="who2021"/> The mechanisms linking air pollution to increased cardiovascular mortality are uncertain, but probably include pulmonary and systemic inflammation.<ref>{{cite journal |last1=Pope |first1=C. A. |title=Cardiovascular Mortality and Long-Term Exposure to Particulate Air Pollution: Epidemiological Evidence of General Pathophysiological Pathways of Disease |journal=Circulation |date=15 December 2003 |volume=109 |issue=1 |pages=71–77 |doi=10.1161/01.CIR.0000108927.80044.7F |pmid=14676145 |doi-access=free}}</ref>

==== Contemporary annual deaths ====
A 2021 study by scientists of U.K. and U.S. universities that uses a high spatial resolution model and an updated concentration-response function concluded that 10.4 million global excess deaths in 2012 and 8.7 million in 2018&nbsp;– or {{tooltip|2=A review of this and a more nuanced assessment of mortality impacts in terms of contribution to death, rather than number of deceased, may be needed|a fifth}}{{dubious|date=March 2021|reason=A review of this and a more nuanced assessment of mortality impacts in terms of contribution to death, rather than number of deceased, may be needed}} – were due to air pollution generated by fossil fuel combustion, significantly higher than earlier estimates and with spatially subdivided mortality impacts.<ref>{{cite news |last1=Green |first1=Matthew |title=Fossil fuel pollution causes one in five premature deaths globally: study |url=https://www.reuters.com/article/us-health-pollution-fossil-idUSKBN2A90UB |access-date=5 March 2021 |work=Reuters |date=9 February 2021 |language=en}}</ref><ref name="10.1016/j.envres.2021.110754">{{cite journal |last1=Vohra |first1=Karn |last2=Vodonos |first2=Alina |last3=Schwartz |first3=Joel |last4=Marais |first4=Eloise A. |last5=Sulprizio |first5=Melissa P. |last6=Mickley |first6=Loretta J. |title=Global mortality from outdoor fine particle pollution generated by fossil fuel combustion: Results from GEOS-Chem |journal=Environmental Research |date=1 April 2021 |volume=195 |pages=110754 |doi=10.1016/j.envres.2021.110754 |pmid=33577774 |bibcode=2021ER....195k0754V |s2cid=231909881 |url=https://www.sciencedirect.com/science/article/abs/pii/S0013935121000487 |access-date=5 March 2021 |language=en |issn=0013-9351}}</ref><!--2018 or later-->

According to the WHO, air pollution accounts for 1 in 8 deaths worldwide.<ref>{{cite news |last1=Whitacre |first1=Paula |title=Air Pollution Accounts for 1 in 8 Deaths Worldwide, According to New WHO Estimates |url=https://www.niehs.nih.gov/research/programs/geh/geh_newsletter/2014/4/articles/air_pollution_accounts_for_1_in_8_deaths_worldwide_according_to_new_who_estimates.cfm |work=[[Organization:National Institute of Environmental Health Sciences|National Institute of Environmental Health Sciences]] |date=9 February 2021 |language=en |access-date=18 February 2022 |archive-date=4 November 2022 |archive-url=https://web.archive.org/web/20221104074908/https://www.niehs.nih.gov/research/programs/geh/geh_newsletter/2014/4/articles/air_pollution_accounts_for_1_in_8_deaths_worldwide_according_to_new_who_estimates.cfm |url-status=dead }}</ref>

=== Cardiovascular disease ===
A 2007 review of evidence found that for the general population, ambient air pollution exposure is a risk factor correlating with increased total mortality from cardiovascular events (range: 12% to 14% per 10&nbsp;µg/m<sup>3</sup> increase).<ref name = longterm>{{cite journal |last1=Chen |first1=H. |last2= Goldberg |first2=M.S. |last3=Villeneuve |first3=P.J. |title=A systematic review of the relation between long-term exposure to ambient air pollution and chronic diseases. |journal=Reviews on Environmental Health |date=Oct–Dec 2008 |volume=23 |issue=4 |pages=243–97 |pmid=19235364 |doi= 10.1515/reveh.2008.23.4.243 |s2cid=24481623}}</ref>{{clarify|exposure duration? age of exposure? regardless of population age?|date=September 2020}}

Air pollution is emerging as a risk factor for stroke, particularly in developing countries where pollutant levels are highest.<ref>{{Cite journal |last1=Mateen |first1=F. J. |last2=Brook |first2=R. D. |title=Air Pollution as an Emerging Global Risk Factor for Stroke |doi=10.1001/jama.2011.352 |journal=JAMA |volume=305 |issue=12 |pages=1240–41 |year=2011 |pmid=21427378}}</ref> A 2007 study found that in women, air pollution is not associated with hemorrhagic but with ischemic stroke.<ref>{{cite journal |last1=Miller |first1=K. A. |last2=Siscovick |first2=D. S. |last3=Sheppard |first3=L. |last4=Shepherd |first4=K. |last5=Sullivan |first5=J. H. |last6=Anderson |first6=G. L. |last7=Kaufman |first7=J. D. |year=2007 |title=Long-term exposure to air pollution and incidence of cardiovascular events in women. |journal=The New England Journal of Medicine |volume=356 |issue=5 |pages=447–58 |doi=10.1056/NEJMoa054409 |pmid=17267905}}</ref> Air pollution was found to be associated with increased incidence and mortality from coronary stroke in a cohort study in 2011.<ref>{{cite journal |last1=Andersen |first1=Z. J. |last2=Kristiansen |first2=L. C. |last3=Andersen |first3=K. K. |last4=Olsen |first4=T. S. |last5=Hvidberg |first5=M. |last6=Jensen |first6=S. S. |last7=Raaschou-Nielsen |first7=O. |year=2011 |title=Stroke and Long-Term Exposure to Outdoor Air Pollution From Nitrogen Dioxide: A Cohort Study |journal=Stroke |volume=43 |issue=2 |pages= 320–25 |doi=10.1161/STROKEAHA.111.629246 |pmid=22052517 |doi-access=free}}</ref> Associations are believed to be causal and effects may be mediated by vasoconstriction, low-grade inflammation and [[Medicine:Atherosclerosis|atherosclerosis]].<ref name="Provost">{{cite journal |last1=Provost |first1=E. |title=Carotid intima-media thickness, a marker of subclinical atherosclerosis, and particulate air pollution exposure: the meta-analytical evidence |journal=PLOS ONE |volume=10 |issue=5 |page=e0127014 |date=May 2015 |doi=10.1371/journal.pone.0127014 |pmid=25970426 |last2=Madhloum |first2=N. |last3=Int Panis |first3=L. |last4=De Boever |first4=P. |last5=Nawrot |first5=T.S. |s2cid=11741224 |pmc=4430520 |bibcode=2015PLoSO..1027014P |doi-access=free}}</ref> Other mechanisms such as autonomic nervous system imbalance have also been suggested.<ref name="AmericanHeartAssociation">{{cite journal |last1=Brook |first1=R.D. |title=Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association |journal=Circulation |volume=121 |issue=21 |pages=2331–78 |year=2010 |doi=10.1161/cir.0b013e3181dbece1 |pmid=20458016 |last2=Rajagopalan |first2=S. |last3=Pope |first3=C.A. III |last4=Brook |first4=J.R. |last5=Bhatnagar |first5=A. |hdl=2027.42/78373 |doi-access=free}}</ref><ref name="Louwies">{{cite journal |last1=Louwies |first1=T. |title=Retinal Microvascular Responses to Short-Term Changes in Particulate Air Pollution in Healthy Adults |journal=Environmental Health Perspectives |volume=121 |issue=9 |pages=1011–16 |year=2013 |doi=10.1289/ehp.1205721 |pmid=23777785 |last2=Int Panis |first2=L. |last3=Kicinski |first3=M. |last4=De Boever |first4=P. |last5=Nawrot |first5=Tim S. |s2cid=6748539 |pmc=3764070}}</ref>

=== Lung disease ===
Research has demonstrated increased risk of developing asthma<ref>{{cite journal |last1=Gehring |first1=U. |last2=Wijga |first2=A. H. |last3=Brauer |first3=M. |last4=Fischer |first4=P. |last5 =de Jongste |first5=J. C. |last6=Kerkhof |first6=M. |last7=Brunekreef |first7=B. |year=2010 |title=Traffic-related air pollution and the development of asthma and allergies during the first 8 years of life |journal=American Journal of Respiratory and Critical Care Medicine |volume=181 |issue=6 |pages=596–603 |doi=10.1164/rccm.200906-0858OC |pmid=19965811}}</ref> and [[Medicine:Chronic obstructive pulmonary disease|chronic obstructive pulmonary disease]] (COPD)<ref>{{cite journal |last1=Andersen |first1=Z. J. |last2=Hvidberg |first2=M. |last3=Jensen |first3=S. S. |last4=Ketzel |first4=M. |last5=Loft |first5=S. |last6=Sorensen |first6=M. |last7=Raaschou-Nielsen |first7=O. |s2cid=3945468 |year=2011 |title=Chronic obstructive pulmonary disease and long-term exposure to traffic-related air pollution: a cohort study. [Research Support, Non-U.S. Gov't]. |journal=American Journal of Respiratory and Critical Care Medicine |volume=183 |issue=4 |pages=455–461 |doi=10.1164/rccm.201006-0937OC |pmid=20870755}}</ref> from increased exposure to traffic-related air pollution. Air pollution has been associated with increased hospitalization and mortality from asthma and COPD.<ref>{{cite journal |author=Committee of the Environmental and Occupational Health Assembly of the American Thoracic Society |year=1996 |title=Health effects of outdoor air pollution |journal=American Journal of Respiratory and Critical Care Medicine |volume=153 |issue=1 |pages=3–50 |doi=10.1164/ajrccm.153.1.8542133 |pmid=8542133}}</ref><ref>{{cite journal |last1=Andersen |first1=Z. J. |last2=Bonnelykke |first2=K. |last3=Hvidberg |first3=M. |last4=Jensen |first4=S. S. |last5=Ketzel |first5=M. |last6=Loft |first6=S. |last7=Raaschou-Nielsen |first7=O. |year=2011 |title=Long-term exposure to air pollution and asthma hospitalisations in older adults: a cohort study |journal=Thorax |volume=67 |issue=1 |pages=6–11 |doi=10.1136/thoraxjnl-2011-200711 |pmid=21890573 |doi-access=free}}</ref> COPD includes diseases such as [[Medicine:Bronchitis#Chronic bronchitis|chronic bronchitis]] and [[Medicine:Pneumatosis#Lungs|emphysema]].<ref>{{cite journal |last=Zoidis |first=John D. |title=The Impact of Air Pollution on COPD |journal=RT: For Decision Makers in Respiratory Care |year=1999 |url=http://www.rtmagazine.com/2007/02/the-impact-of-air-pollution-on-copd/}}</ref> The risk of lung disease from air pollution is greatest for the following groups of people: infants and young children, whose normal breathing is faster than that of older children and adults; the elderly; those who work outside or spend a lot of time outside; and those who have heart or lung disease.<ref>{{Cite web |title=Understanding Air Pollution |url=https://resphealth.org/clean-air/understanding-air-pollution/ |access-date=2022-08-15 |website=Respiratory Health Association |language=en}}</ref>

A study conducted in 1960–1961 in the wake of the Great Smog of 1952 compared 293 London residents with 477 residents of Gloucester, Peterborough, and Norwich, three towns with low reported death rates from chronic bronchitis. All subjects were male postal truck drivers aged 40 to 59. Compared to the subjects from the outlying towns, the London subjects exhibited more severe respiratory symptoms (including cough, phlegm, and dyspnea), reduced lung function (FEV<sub>1</sub> and peak flow rate), and increased sputum production and purulence. The differences were more pronounced for subjects aged 50 to 59. The study controlled for age and smoking habits, so concluded that air pollution was the most likely cause of the observed differences.<ref>Holland WW, Reid DD. "The urban factor in chronic bronchitis" ''Lancet'' 1965;I:445–448.</ref>
More studies have shown that air pollution exposure from traffic reduces lung function development in children<ref name="Gauderman">{{cite journal |last=Gauderman |first=W. |s2cid=852646 |title=Effect of exposure to traffic on lung development from 10 to 18 years of age: a cohort study |journal=The Lancet |volume=369 |issue=9561 |pages=571–77 |year=2007 |doi=10.1016/S0140-6736(07)60037-3 |pmid=17307103 |citeseerx=10.1.1.541.1258}}</ref> and lung function may be compromised by air pollution even at low concentrations.<ref name="IntPanis">{{cite journal |last=Int Panis |first=L. |s2cid=20491472 |title=Short-term air pollution exposure decreases lung function: a repeated measures study in healthy adults |journal=Environmental Health |volume=16 |issue=1 |pages=60 |year=2017 |doi=10.1186/s12940-017-0271-z |doi-access=free |pmid=28615020 |pmc=5471732|bibcode=2017EnvHe..16...60I }}</ref>

It is believed that much like [[Medicine:Cystic fibrosis|cystic fibrosis]], by living in a more urban environment serious health hazards become more apparent. Studies have shown that in urban areas people experience [[Biology:Mucus|mucus]] hypersecretion, lower levels of lung function, and more self-diagnosis of chronic bronchitis and emphysema.<ref>{{cite journal |journal=European Respiratory Journal |title=Urban air pollution and Chronic Obstructive Pulmonary disease: a review |first=J. |last=Sunyer |year=2001 |volume=17 |pages=1024–33 |doi=10.1183/09031936.01.17510240 |pmid=11488305 |issue=5 |doi-access=free}}</ref>

COPD comprises a spectrum of clinical disorders that include emphysema, bronchiectasis, and chronic bronchitis. COPD risk factors are both genetic and environmental. Elevated particle pollution contributes to the exacerbation of this disease and likely its pathogenesis.<ref>{{Cite web |title=Ambient air pollution |url=https://www.who.int/data/gho/data/themes/topics/indicator-groups/indicator-group-details/GHO/ambient-air-pollution |access-date=2023-11-10 |website=www.who.int |language=en}}</ref>

=== Cancer (lung cancer) ===
[[File:DARK CLOUDS OF FACTORY SMOKE OBSCURE CLARK AVENUE BRIDGE - NARA - 550179.jpg|thumb|upright|Unprotected exposure to PM<sub>2.5</sub> air pollution can be equivalent to smoking multiple cigarettes per day,<ref>{{Cite web |url=https://www.cleanairresources.com/data |title=Education Data, Visualizations & Graphics on Air Quality and PM2.5 |website=www.cleanairresources.com |language=en |access-date=19 September 2019}}</ref> potentially increasing the risk of cancer, which is mainly the result of environmental factors.<ref name="BBC-20151217">{{cite news |last=Gallagher |first=James |title=Cancer is not just 'bad luck' but down to environment, study suggests |url=https://www.bbc.co.uk/news/health-35111449 |date=17 December 2015 |work=BBC |access-date=17 December 2015}}</ref>|alt=]]
Around 300,000 lung cancer deaths were attributed globally in 2019 to exposure to fine particulate matter, PM<sub>2.5</sub>, contained in air pollution.<ref name=":2">{{Cite news|date=2022-09-10 |title=Cancer breakthrough is a 'wake-up' call on danger of air pollution |url=https://www.theguardian.com/science/2022/sep/10/cancer-breakthrough-is-a-wake-up-call-on-danger-of-air-pollution |access-date=2022-09-11 |work={{wipe|The Guardian}} |language=en}}</ref>

A review of evidence regarding whether ambient air pollution exposure is a risk factor for cancer in 2007 found solid data to conclude that long-term exposure to PM<sub>2.5</sub> (fine particulates) increases the overall risk of non-accidental mortality by 6% per a 10 μg/m<sup>3</sup> increase. Exposure to PM<sub>2.5</sub> was also associated with an increased risk of mortality from lung cancer (range: 15–21% per 10 μg/m<sup>3</sup> increase) and total cardiovascular mortality (range: 12–14% per a 10 μg/m<sup>3</sup> increase).<ref name="longterm" />

The review further noted that living close to busy traffic appears to be associated with elevated risks of these three outcomes&nbsp;– increase in lung cancer deaths, cardiovascular deaths, and overall non-accidental deaths. The reviewers also found suggestive evidence that exposure to PM<sub>2.5</sub> is positively associated with mortality from coronary heart diseases and exposure to SO<sub>2</sub> increases mortality from lung cancer, but the data was insufficient to provide solid conclusions.<ref name="longterm" /> Another investigation showed that higher activity level increases deposition fraction of aerosol particles in human lung and recommended avoiding heavy activities like running in outdoor space at polluted areas.<ref name="Saber2012">{{cite journal |last1=Saber |first1=E.M. |last2=Heydari |first2=G. |title=Flow patterns and deposition fraction of particles in the range of 0.1–10 μm at trachea and the first third generations under different breathing conditions |journal=[[Medicine:Computers in Biology and Medicine|Computers in Biology and Medicine]] |date=May 2012 |volume=42 |issue=5 |pages=631–38 |doi=10.1016/j.compbiomed.2012.03.002 |pmid=22445097}}</ref>

In 2011, a large Danish epidemiological study found an increased risk of lung cancer for people who lived in areas with high nitrogen oxide concentrations. In this study, the association was higher for non-smokers than smokers.<ref>{{cite journal |last1=Raaschou-Nielsen |first1=O. |last2=Andersen |first2=Z. J. |last3=Hvidberg |first3=M. |last4=Jensen |first4=S. S. |last5=Ketzel |first5=M. |last6=Sorensen |first6=M. |last7=Tjonneland |first7=A. |s2cid=1323189 |year=2011 |title=Lung cancer incidence and long-term exposure to air pollution from traffic. [Research Support, Non-U.S. Gov't]. |journal=Environmental Health Perspectives |volume=119 |issue=6 |pages=860–65 |doi=10.1289/ehp.1002353 |pmid=21227886 |pmc=3114823}}</ref> An additional Danish study, also in 2011, likewise noted evidence of possible associations between air pollution and other forms of cancer, including cervical cancer and brain cancer.<ref>{{cite journal |last1=Raaschou-Nielsen |first1=O. |last2=Andersen |first2=Z. J. |last3=Hvidberg |first3=M. |last4=Jensen |first4=S. S. |last5=Ketzel |first5=M. |last6=Sorensen |first6=M. |last7=Tjonneland |first7=A. |s2cid=376897 |year=2011 |title=Air pollution from traffic and cancer incidence: a Danish cohort study |journal=Environmental Health |volume=10 |issue=1 |page=67 |doi=10.1186/1476-069X-10-67 |doi-access=free |pmid=21771295 |pmc=3157417|bibcode=2011EnvHe..10...67R }}</ref>

A study presented in 2022 outlined the biological basis for how air pollution causes cancer.<ref name=":2" />

=== Kidney disease ===
In 2021, a study of 163,197 Taiwanese residents over the period of 2001–2016 estimated that every 5 [[Microgram|μg]]/m<sup>3</sup> decrease in the ambient concentration of PM<sub>2.5</sub> was associated with a 25% reduced risk of [[Medicine:Chronic kidney disease|chronic kidney disease]] development.<ref name="Bo2021">{{cite journal |author=Yacong Bo |year=2021 |title=Reduced Ambient PM2.5 Was Associated with a Decreased Risk of Chronic Kidney Disease: A Longitudinal Cohort Study |journal=Environmental Science & Technology |volume=55 |issue=10 |pages=6876–6883 |doi=10.1021/acs.est.1c00552 |pmid=33904723 |bibcode=2021EnST...55.6876B |s2cid=233408693}}</ref> According to a chord study involving 10,997 atherosclerosis patients, higher PM 2.5 exposure is associate with increased albuminuria.<ref>{{Cite journal |last1=Blum |first1=Matthew F. |last2=Surapaneni |first2=Aditya |last3=Stewart |first3=James D. |last4=Liao |first4=Duanping |last5=Yanosky |first5=Jeff D. |last6=Whitsel |first6=Eric A. |last7=Power |first7=Melinda C. |last8=Grams |first8=Morgan E. |date=2020-03-06 |title=Particulate Matter and Albuminuria, Glomerular Filtration Rate, and Incident CKD |url=https://cjasn.asnjournals.org/content/15/3/311 |journal=Clinical Journal of the American Society of Nephrology |language=en |volume=15 |issue=3 |pages=311–319 |doi=10.2215/CJN.08350719 |issn=1555-9041 |pmc=7057299 |pmid=32108020}}</ref>

=== Fertility ===

==== NO<sub>2</sub> ====
In women undergoing [[Biology:In vitro fertilisation|IVF]] treatment, increases in NO<sub>2</sub> both at the patient's address and by the IVF lab were significantly associated with a lower live birth rate.<ref name=":02">{{Cite journal |last1=Conforti |first1=Alessandro |last2=Mascia |first2=Marika |last3=Cioffi |first3=Giuseppina |last4=De Angelis |first4=Cristina |last5=Coppola |first5=Giuseppe |last6=De Rosa |first6=Pasquale |last7=Pivonello |first7=Rosario |last8=Alviggi |first8=Carlo |last9=De Placido |first9=Giuseppe |date=2018-12-30 |title=Air pollution and female fertility: a systematic review of literature |journal=Reproductive Biology and Endocrinology |volume=16 |issue=1 |pages=117 |doi=10.1186/s12958-018-0433-z |doi-access=free |issn=1477-7827 |pmc=6311303 |pmid=30594197}}</ref>

In the general population, there is a significant increase in [[Medicine:Miscarriage|miscarriage]] rate in women exposed to NO<sub>2</sub> compared to the non-exposed group.<ref name=":02" />

==== CO ====
CO exposure is significantly associated with [[Medicine:Stillbirth|stillbirth]] in the second and third trimester.<ref name=":02" />
[[File:Benzo-a-pyrene chemical structure.png|thumb|Standard line-angle structure of benzo-a-pyrene (BaP)]]

==== Polycyclic aromatic hydrocarbons ====
[[Astronomy:Polycyclic aromatic hydrocarbon|Polycyclic aromatic hydrocarbon]]s (PAHs) have been associated with reduced fertility. Benzo(a)pyrene (BaP) is a well-known PAH and carcinogen which is often found in exhaust fumes and cigarette smoke.<ref>{{Cite journal |last1=Canipari |first1=Rita |last2=De Santis |first2=Lucia |last3=Cecconi |first3=Sandra |date=January 2020 |title=Female Fertility and Environmental Pollution |journal=International Journal of Environmental Research and Public Health |language=en |volume=17 |issue=23 |pages=8802 |doi=10.3390/ijerph17238802 |issn=1660-4601 |pmc=7730072 |pmid=33256215|doi-access=free }}</ref> PAHs have been reported to administer their toxic effects through oxidative stress by increasing the production of [[Biology:Reactive oxygen species|Reactive Oxygen Species]] (ROS) which can result in inflammation and cell death. More long-term exposure to PAHs can result in DNA damage and reduced repair.<ref>{{Cite journal |last1=da Silva Junior |first1=Francisco Carlos |last2=Felipe |first2=Maria Beatriz Mesquita Cansanção |last3=Castro |first3=Denis Elvis Farias de |last4=Araújo |first4=Sinara Carla da Silva |last5=Sisenando |first5=Herbert Costa Nóbrega |last6=Batistuzzo de Medeiros |first6=Silvia Regina |date=2021-06-01 |title=A look beyond the priority: A systematic review of the genotoxic, mutagenic, and carcinogenic endpoints of non-priority PAHs |url=https://www.sciencedirect.com/science/article/pii/S0269749121004188 |journal=Environmental Pollution |language=en |volume=278 |pages=116838 |doi=10.1016/j.envpol.2021.116838 |pmid=33714059 |s2cid=232222865 |issn=0269-7491}}</ref>

Exposure to BaP has been reported to reduce [[Medicine:Sperm motility|sperm motility]] and increasing the exposure worsens this effect. Research has demonstrated that more BaPs were found in men with reported fertility issues compared to men without.<ref>{{Cite journal |last1=Plunk |first1=Elizabeth C. |last2=Richards |first2=Sean M. |date=January 2020 |title=Endocrine-Disrupting Air Pollutants and Their Effects on the Hypothalamus-Pituitary-Gonadal Axis |journal=International Journal of Molecular Sciences |language=en |volume=21 |issue=23 |pages=9191 |doi=10.3390/ijms21239191 |issn=1422-0067 |pmc=7731392 |pmid=33276521|doi-access=free }}</ref>

Studies have shown that BaPs can affect [[Biology:Folliculogenesis|folliculogenesis]] and ovarian development by reducing the number of ovarian germ cells via triggering cell death pathways and inducing inflammation which can lead to ovarian damage.<ref>{{Cite journal |last1=Perono |first1=Genevieve A |last2=Petrik |first2=James J |last3=Thomas |first3=Philippe J |last4=Holloway |first4=Alison C |date=2022-01-01 |title=The effects of polycyclic aromatic compounds (PACs) on mammalian ovarian function |journal=Current Research in Toxicology |language=en |volume=3 |pages=100070 |doi=10.1016/j.crtox.2022.100070 |issn=2666-027X |pmc=9043394 |pmid=35492299}}</ref>

==== Particulate matter ====
[[Earth:Particulate pollution|Particulate matter (PM)]] refers to the collection of solids and liquids suspended in the air. These can be harmful to humans when exposed to in day-to-day life, and more research has shown that these effects may be more extensive than first thought; particularly on male fertility. Within the spectrum of PM there are different weights, such as PM<sub>2.5</sub> which are tiny particles of 2.5 microns in width or smaller, compared with PM<sub>10</sub> which are classified as 10 microns in diameter or less.

In a study based in California it was found that as exposure to PM<sub>2.5</sub> increased sperm motility decreased and morphology became more abnormal. Similarly, in Poland exposure to PM<sub>2.5</sub> and PM<sub>10</sub> lead to an increase in the percentage of cells with immature [[Biology:Chromatin|chromatin]] (DNA that has not fully developed or has developed abnormally).<ref name=":5">{{Cite journal |last1=Jurewicz |first1=Joanna |last2=Dziewirska |first2=Emila |last3=Radwan |first3=Michał |last4=Hanke |first4=Wojciech |date=2018-12-23 |title=Air pollution from natural and anthropic sources and male fertility |journal=Reproductive Biology and Endocrinology |language=en |volume=16 |issue=1 |pages=109 |doi=10.1186/s12958-018-0430-2 |doi-access=free |issn=1477-7827 |pmc=6304234 |pmid=30579357}}</ref>

In Turkey, a study looked at the fertility of men who work as toll collectors and are therefore exposed to high levels of traffic pollutants daily. Traffic pollution often has high levels of PM<sub>10</sub> alongside [[Chemistry:Carbon monoxide|carbon monoxide]] and nitrous oxides.<ref name=":5" /> In this study group there were significant differences in sperm count and motility when compared to a control group with limited air pollution exposure.

In women, whilst overall effects on fertility did not seem significant there was an association was found between increased exposure to PM<sub>10</sub> and early miscarriage. Exposure to smaller particulate matter, PM<sub>2.5</sub>, was seen to have an effect on conception rates in women undergoing [[Biology:In vitro fertilisation|IVF]] but not with live birth rates.<ref name=":02" />
[[File:Ozone-structure.png|thumb|Ozone structure showing three oxygen atoms]]

==== Ground-level ozone pollution ====
[[Earth:Ground-level ozone|Ground-level ozone]] (O<sub>3</sub>), when in high concentrations, is regarded as an air pollutant and is often found in smog in industrial areas. O<sub>3</sub> is largely produced by chemical reactions involving NO<sub>x</sub> gases (nitrous oxides, especially from combustion) and volatile organic compounds in the presence of sunlight.

There is limited research about the effect that ozone pollution has on fertility.<ref name=":02" /> At present, there is no evidence to suggest that ozone exposure poses a deleterious effect on spontaneous fertility in either females or males. However, there have been studies which suggest that high levels of ozone pollution, often a problem in the summer months, exert an effect on in vitro fertilisation (IVF) outcomes. Within an IVF population, NO<sub>x</sub> and ozone pollutants were linked with reduced rates of live birth'''.'''<ref name=":02" />

While most research on this topic is focused on the direct human exposure of air pollution, other studies have analysed the impact of air pollution on gametes and embryos within IVF laboratories. Multiple studies have reported a marked improvement in embryo quality, [[Biology:Implantation (embryology)|implantation]] and pregnancy rates after IVF laboratories have implemented air filters in a concerted effort to reduce levels of air pollution.<ref name=":3">{{Cite journal |last1=Frutos |first1=Víctor |last2=González-Comadrán |first2=Mireia |last3=Solà |first3=Ivan |last4=Jacquemin |first4=Benedicte |last5=Carreras |first5=Ramón |last6=Checa Vizcaíno |first6=Miguel A. |date=2015-01-02 |title=Impact of air pollution on fertility: a systematic review |url=https://doi.org/10.3109/09513590.2014.958992 |journal=Gynecological Endocrinology |volume=31 |issue=1 |pages=7–13 |doi=10.3109/09513590.2014.958992 |issn=0951-3590 |pmid=25212280|s2cid=41594539 }}</ref> Therefore, ozone pollution is considered to have a negative impact on the success of [[Engineering:Assisted reproductive technology|assisted reproductive technologies]] (ART) when occurring at high levels.

Ozone is thought to act in a biphasic manner where a positive effect on live birth is observed when ozone exposure is limited to before IVF embryo implantation.<ref>{{Cite journal |last1=Checa Vizcaíno |first1=Miguel A. |last2=González-Comadran |first2=Mireia |last3=Jacquemin |first3=Benedicte |date=September 2016 |title=Outdoor air pollution and human infertility: a systematic review |url=http://dx.doi.org/10.1016/j.fertnstert.2016.07.1110 |journal=Fertility and Sterility |volume=106 |issue=4 |pages=897–904.e1 |doi=10.1016/j.fertnstert.2016.07.1110 |pmid=27513553 |issn=0015-0282}}</ref> Conversely, a negative effect is demonstrated upon exposure to ozone after embryo implantation.<ref name=":4">{{Cite journal |last1=Carré |first1=Julie |last2=Gatimel |first2=Nicolas |last3=Moreau |first3=Jessika |last4=Parinaud |first4=Jean |last5=Léandri |first5=Roger |date=2017-07-28 |title=Does air pollution play a role in infertility?: a systematic review |journal=Environmental Health |volume=16 |issue=1 |pages=82 |doi=10.1186/s12940-017-0291-8 |doi-access=free |issn=1476-069X |pmc=5534122 |pmid=28754128|bibcode=2017EnvHe..16...82C }}</ref>

Retrospective and prospective studies evaluating the effect of several traffic pollutants (of which ground-level ozone is one) highlighted a significant decrease in live birth rates and miscarriages.<ref name=":3" />

In terms of male fertility, ozone is reported to cause a significant decrease in sperm concentration measured in semen after exposure.<ref>{{Cite journal |title=Air pollution from natural and anthropic sources and male fertility |url=https://rdcu.be/cWWgF |access-date=2022-10-05 |journal=Reproductive Biology and Endocrinology |year=2018 |doi=10.1186/s12958-018-0430-2 |doi-access=free |language=en |last1=Jurewicz |first1=Joanna |last2=Dziewirska |first2=Emila |last3=Radwan |first3=Michał |last4=Hanke |first4=Wojciech |volume=16 |issue=1 |page=109 |pmid=30579357 |pmc=6304234 |s2cid=57376088 }}</ref> Similarly, sperm vitality, the proportion of alive spermatozoa in a sample, was demonstrated to be diminished in a handful of studies.<ref name=":4" /> This demonstrates that ozone air pollution exhibits a significantly negative effect of air pollution on this parameter. However, findings on the effect of ozone exposure on male fertility are somewhat discordant, highlighting the need for further research.<ref name=":4" />

=== Children ===
In the United States, despite the passage of the Clean Air Act in 1970, in 2002 at least 146 million Americans were living in non-attainment areas&nbsp;– regions in which the concentration of certain air pollutants exceeded federal standards.<ref>{{cite journal |author=Committee on Environmental Health |title=Ambient Air Pollution: Health Hazards to Children |journal=Pediatrics |volume=114 |issue=6 |year=2004 |pages=1699–707 |doi=10.1542/peds.2004-2166 |pmid=15574638 |doi-access=free}}</ref> These dangerous pollutants are known as the criteria pollutants, and include ozone, particulate matter, sulfur dioxide, nitrogen dioxide, carbon monoxide, and lead. Protective measures to ensure children's health are being taken in cities such as New Delhi, India, where buses now use [[Chemistry:Compressed natural gas|compressed natural gas]] to help eliminate the "pea-soup" smog.<ref>{{cite web | publisher = [[Organization:World Health Organization|World Health Organization]] | title = Polluted Cities: The Air Children Breathe| url =https://www.who.int/ceh/publications/en/11airpollution.pdf}}</ref> A 2015 study in Europe has found that exposure to [[Physics:Ultrafine particle|ultrafine]] particles can increase blood pressure in children.<ref name="UFPBPChildren">{{cite journal |last1=Pieters |first1=N. |title=Blood Pressure and Same-Day Exposure to Air Pollution at School: Associations with Nano-Sized to Coarse PM in Children |journal=Environmental Health Perspectives |volume=123 |issue=7 |pages=737–42 |date=March 2015 |doi=10.1289/ehp.1408121 |pmid=25756964 |last2=Koppen |first2=G. |last3=Van Poppel |first3=M. |last4=De Prins |first4=S. |last5=Cox |first5=B. |last6=Dons |first6=E. |last7=Nelen |first7=V. |last8=Int Panis |first8=L. |last9=Plusquin |first9=M. |last10=Schoeters |first10=G. |last11=Nawrot |first11=T.S. |pmc=4492263}}</ref> In a 2018 WHO report, polluted air leads to the poisoning of millions of children under the age of 15, resulting in the death of some six hundred thousand children annually.<ref>{{cite web|author=AFP |url=https://www.thenews.com.pk/print/387232-air-pollution-kills-600-000-children-who |title= Air pollution kills 600,000 children: WHO |publisher=The News International |date= 30 October 2018 |access-date=30 October 2018}}</ref>

==== Prenatal exposure ====
Prenatal exposure to polluted air has been linked to a variety of [[Medicine:Neurodevelopmental disorder|neurodevelopmental disorder]]s in children. For example, exposure to polycyclic aromatic hydrocarbons (PAH) was associated with reduced IQ scores and symptoms of [[Medicine:Anxiety disorder|anxiety]] and [[Medicine:Depression (mood)|depression]].<ref>{{Cite journal|last1=Perera |first1=Frederica P. |last2=Tang |first2=Deliang |last3=Wang |first3=Shuang |last4=Vishnevetsky |first4=Julia |last5=Zhang |first5=Bingzhi |last6=Diaz |first6=Diurka |last7=Camann |first7=David |last8=Rauh |first8=Virginia |date=1 June 2012 |title=Prenatal Polycyclic Aromatic Hydrocarbon (PAH) Exposure and Child Behavior at Age 6–7 Years |url= |journal=Environmental Health Perspectives |volume=120 |issue=6 |pages=921–926 |doi=10.1289/ehp.1104315 |pmc=3385432 |pmid=22440811}}</ref> They can also lead to detrimental perinatal health outcomes that are often fatal in developing countries.<ref name="10.1371/journal.pmed.1003718"/> A 2014 study found that PAHs might play a role in the development of childhood [[Medicine:Attention deficit hyperactivity disorder|attention deficit hyperactivity disorder]] (ADHD).<ref>{{Cite journal|last1=Perera |first1=Frederica P. |last2=Chang |first2=Hsin-wen |last3=Tang |first3=Deliang |last4=Roen |first4=Emily L. |last5=Herbstman |first5=Julie |last6=Margolis |first6=Amy |last7=Huang |first7=Tzu-Jung |last8=Miller |first8=Rachel L. |last9=Wang |first9=Shuang |last10=Rauh |first10=Virginia |date=5 November 2014 |title=Early-Life Exposure to Polycyclic Aromatic Hydrocarbons and ADHD Behavior Problems |url= |journal=PLOS ONE |language=en |volume=9 |issue=11 |pages=e111670 |doi=10.1371/journal.pone.0111670 |issn=1932-6203 |pmc=4221082 |pmid=25372862 |bibcode=2014PLoSO...9k1670P |doi-access=free}}</ref>

Researchers have begun to find evidence for air pollution as a risk factor for [[Medicine:Autism spectrum|autism spectrum disorder]] (ASD). In Los Angeles, children who were living in areas with high levels of traffic-related air pollution were more likely to be diagnosed with autism between three–five years of age.<ref>{{Cite journal |last1=Becerra |first1=Tracy Ann |last2=Wilhelm |first2=Michelle |last3=Olsen |first3=Jørn |last4=Cockburn |first4=Myles |last5=Ritz |first5=Beate |date=1 March 2013 |title=Ambient Air Pollution and Autism in Los Angeles County, California |url= |journal=Environmental Health Perspectives |volume=121 |issue=3 |pages=380–386 |doi=10.1289/ehp.1205827 |pmc=3621187 |pmid=23249813}}</ref> The connection between air pollution and neurodevelopmental disorders in children is thought to be related to epigenetic dysregulation of the primordial germ cells, embryo, and fetus during a critical period. Some PAHs are considered endocrine disruptors and are lipid soluble. When they build up in adipose tissue, they can be transferred across the placenta.<ref>{{Cite journal |last1=Perera |first1=Frederica |last2=Herbstman |first2=Julie |date=1 April 2011 |title=Prenatal environmental exposures, epigenetics, and disease |url= |journal=Reproductive Toxicology |series=Prenatal Programming and Toxicity II (PPTOX II): Role of Environmental Stressors in the Developmental Origins of Disease |language=en |volume=31 |issue=3 |pages=363–373 |doi=10.1016/j.reprotox.2010.12.055 |pmid=21256208 |issn=0890-6238 |pmc=3171169}}</ref> Air pollution has been associated with the prevalence of preterm births.<ref>{{Cite journal |last1=Papamitsou |first1=T. |last2=Sirak |first2=S. |last3=Kavvadas |first3=D. |date=January–March 2020 |title=Air pollution and preterm birth: a recommendation for further study in Greece |journal=Hippokratia |volume=24 |issue=1 |pages=44 |pmc=7733367 |pmid=33364740}}</ref>

==== Infants ====
Ambient levels of air pollution have been associated with [[Medicine:Preterm birth|preterm birth]] and [[Medicine:Low birth weight|low birth weight]]. A 2014 WHO worldwide survey on maternal and perinatal health found a statistically significant association between low birth weights (LBW) and increased levels of exposure to PM<sub>2.5</sub>. Women in regions with greater than average PM<sub>2.5</sub> levels had statistically significant higher odds of pregnancy resulting in a low-birth weight infant even when adjusted for country-related variables.<ref>{{Cite journal|last1=Fleischer |first1=Nancy L. |last2=Merialdi |first2=Mario |last3=van Donkelaar |first3=Aaron |last4=Vadillo-Ortega |first4=Felipe |last5=Martin |first5=Randall V. |last6=Betran |first6=Ana Pilar |last7=Souza |first7=João Paulo |s2cid=3947454 |date=1 April 2014|title=Outdoor air pollution, preterm birth, and low birth weight: analysis of the World Health Organization global survey on maternal and perinatal health |journal=Environmental Health Perspectives |volume=122 |issue=4 |pages=425–30 |doi=10.1289/ehp.1306837 |issn=1552-9924 |pmc=3984219 |pmid=24508912}}</ref> The effect is thought to be from stimulating [[Medicine:Inflammation|inflammation]] and increasing [[Biology:Oxidative stress|oxidative stress]].

A study by the University of York found that in 2010 exposure to PM<sub>2.5</sub> was strongly associated with 18% of preterm births globally, which was approximately 2.7 million premature births. The countries with the highest air pollution associated preterm births were in South and East Asia, the Middle East, North Africa, and West sub-Saharan Africa.<ref name=":0">{{Cite journal|last1=Malley |first1=Christopher S. |last2=Kuylenstierna |first2=Johan C. I. |last3=Vallack |first3=Harry W. |last4=Henze |first4=Daven K. |last5=Blencowe |first5=Hannah |last6=Ashmore |first6=Mike R. |date=1 April 2017 |title=Preterm birth associated with maternal fine particulate matter exposure: A global, regional and national assessment |journal=Environment International |volume=101 |pages=173–82 |doi=10.1016/j.envint.2017.01.023 |issn=1873-6750 |pmid=28196630 |url=http://eprints.whiterose.ac.uk/112553/1/Malley_2017_Environment_International.pdf |doi-access=free}}</ref> In 2019, ambient particulate matter pollution in Africa resulted in at least 383,000 early deaths, according to new estimates of the cost of air pollution in the continent. This increased from 3.6% in 1990 to around 7.4% of all premature deaths in the area.<ref>{{Cite book |last=Bank |first=European Investment |url=https://www.eib.org/en/publications/finance-in-africa-navigating-the-financial-landscape-in-turbulent-times |title=Finance in Africa - Navigating the financial landscape in turbulent times |date=2022-10-19 |publisher=European Investment Bank |isbn=978-92-861-5382-2 |language=EN}}</ref><ref>{{Cite web |title=Silent Suffocation in Africa - Air Pollution is a Growing Menace, Affecting the Poorest Children the Most |url=https://www.unicef.org/media/55081/file/Silent_suffocation_in_africa_air_pollution_2019.pdf |website=UNICEF}}</ref><ref>{{Cite web |title=The cost of air pollution in Africa |url=https://www.un.org/africarenewal/documents/cost-air-pollution-africa |access-date=2022-10-31 |website=Africa Renewal |language=en}}</ref>

The source of PM<sub>2.5</sub> differs greatly by region. In South and East Asia, pregnant women are frequently exposed to indoor air pollution because of wood and other [[Biology:Biomass heating system|biomass]] fuels being used for cooking, which are responsible for more than 80% of regional pollution. In the Middle East, North Africa and West sub-Saharan Africa, fine PM comes from natural sources, such as [[Earth:Dust storm|dust storm]]s.<ref name=":0" /> The United States had an estimated 50,000 preterm births associated with exposure to PM<sub>2.5</sub> in 2010.<ref name=":0" />

A study between 1988 and 1991 found a correlation between [[Chemistry:Sulfur dioxide|sulfur dioxide]] (SO<sub>2</sub>) and total suspended particulates (TSP) and preterm births and low birth weights in Beijing. A group of 74,671 pregnant women, in four separate regions of Beijing, were monitored from early pregnancy to delivery along with daily air pollution levels of sulfur Dioxide and TSP (along with other particulates). The estimated reduction in birth weight was 7.3 g for every 100&nbsp;µg/m<sup>3</sup> increase in {{SO2}} and 6.9 g for each 100&nbsp;µg/m<sup>3</sup> increase in TSP. These associations were statistically significant in both summer and winter, although, summer was greater. The proportion of low birth weight attributable to air pollution, was 13%. This is the largest attributable risk ever reported for the known risk factors of low birth weight.<ref>{{Cite journal |last1=Wang |first1=X. |last2=Ding |first2=H. |last3=Ryan |first3=L. |last4=Xu |first4=X. |s2cid=2707126 |date=1 May 1997 |title=Association between air pollution and low birth weight: a community-based study |journal=Environmental Health Perspectives |volume=105 |issue=5 |pages=514–20 |issn=0091-6765 |pmc=1469882 |pmid=9222137 |doi=10.1289/ehp.97105514}}</ref> Coal stoves, which are in 97% of homes, are a major source of air pollution in this area.

Brauer et al. studied the relationship between air pollution and proximity to a highway with pregnancy outcomes in a Vancouver cohort of pregnant woman using addresses to estimate exposure during pregnancy. Exposure to NO, NO<sub>2</sub>, CO, PM<sub>10</sub> and PM<sub>2.5</sub> were associated with infants born small for gestational age (SGA). Women living less than 50 meters away from an expressway or highway were 26% more likely to give birth to a SGA infant.<ref>{{Cite journal |last1=Brauer |first1=Michael |last2=Lencar |first2=Cornel |last3=Tamburic |first3=Lillian |last4=Koehoorn |first4=Mieke |last5=Demers |first5=Paul |last6=Karr |first6=Catherine |s2cid=7721551 |date=1 May 2008 |title=A Cohort Study of Traffic-Related Air Pollution Impacts on Birth Outcomes |journal=Environmental Health Perspectives |volume=116 |issue=5 |pages=680–6 |doi=10.1289/ehp.10952 |pmc=2367679 |pmid=18470315}}</ref>

=== "Clean" areas ===
[[File:Share of the population exposed to air pollution levels above WHO guidelines, OWID.svg|thumb|upright=1.75|The share of the population exposed to air pollution levels above WHO guidelines, 2016]]
Even in areas with relatively low levels of air pollution, public health effects can be significant and costly, since a large number of people breathe in such pollutants. A study published in 2017 found that even in areas of the U.S. where ozone and PM<sub>2.5</sub> meet federal standards, Medicare recipients who are exposed to more air pollution have higher mortality rates.<ref name="NEJM0617">{{cite journal |last=Qian |first=Di |s2cid=12038778 |date=29 June 2017 |title=Air Pollution and Mortality in the Medicare Population |journal=New England Journal of Medicine |volume=376 |issue=26 |pages=2513–2522 |doi=10.1056/NEJMoa1702747 |pmid=28657878 |pmc=5766848}}</ref>

A 2005 scientific study for the British Columbia Lung Association showed that a small improvement in air quality (1% reduction of ambient PM<sub>2.5</sub> and ozone concentrations) would produce $29 million in annual savings in the Metro Vancouver region in 2010.<ref>{{cite web|url=http://www.bc.lung.ca/pdf/health_and_air_quality_2005.pdf |title=2005 BC Lung Association report on the valuation of health impacts from air quality in the Lower Fraser Valley airshed |access-date=29 August 2010 |url-status=dead|archive-url=https://web.archive.org/web/20110515185052/http://www.bc.lung.ca/pdf/health_and_air_quality_2005.pdf |archive-date=15 May 2011}}</ref> This finding is based on health valuation of lethal (death) and sub-lethal (illness) affects. A study published in 2022 found that rural population in India, like those in urban areas, are also exposed to high levels of air pollution.<ref>{{Cite journal |last1=Pathak |first1=Mansi |last2=Kuttippurath |first2=Jayanarayanan |date=2022 |title=Air quality trends in rural India: analysis of NO2 pollution using satellite measurements |url=https://pubs.rsc.org/en/content/articlelanding/2022/EM/D2EM00293K |journal=Environmental Science: Processes & Impacts |language=en |volume=24 |issue=12 |pages=2437–2449 |doi=10.1039/D2EM00293K |pmid=36413251 |s2cid=253261324 |issn=2050-7887}}</ref>

In 2020, scientists found that the [[Earth:Planetary boundary layer|boundary layer air]] over the Southern Ocean around Antarctica is 'unpolluted' by humans.<ref>{{Cite web|last=Woodyatt|first=Amy|date=3 June 2020|title=Scientists say they have found the cleanest air on Earth|url=https://www.cnn.com/2020/06/02/world/cleanest-air-intl-scli-scn-climate/index.html|access-date=3 June 2020|website=CNN}}</ref>

=== Central nervous system ===
Data is accumulating that air pollution exposure also affects the [[Biology:Central nervous system|central nervous system]].<ref name="bos">{{cite journal |last1=Bos |first1=I. |title=Physical Activity, Air Pollution and the Brain. |journal=Sports Medicine |volume=44 |issue=11 |pages=1505–18 |year=2014 |url=https://www.researchgate.net/publication/264793941 |doi=10.1007/s40279-014-0222-6 |pmid=25119155 |last2=De Boever |first2=P. |last3=Int Panis |first3=L. |last4=Meeusen |first4=R. |s2cid=207493297}}</ref>

Air pollution increases the risk of dementia in people over 50 years old.<ref>[https://www.theguardian.com/environment/2018/sep/18/air-pollution-causes-jump-in-dementia-risk-study-suggests Air pollution linked to much greater risk of dementia] ''{{wipe|The Guardian}}''</ref> Childhood indoor air pollution may negatively affect cognitive function and neurodevelopment.<ref>{{cite journal |last1=Julvez |first1=Jordi |last2=López-Vicente |first2=Mónica |last3=Warembourg |first3=Charline |last4=Maitre |first4=Lea |last5=Philippat |first5=Claire |last6=Gützkow |first6=Kristine B. |last7=Guxens |first7=Monica |last8=Evandt |first8=Jorunn |last9=Andrusaityte |first9=Sandra |last10=Burgaleta |first10=Miguel |last11=Casas |first11=Maribel |last12=Chatzi |first12=Leda |last13=de Castro |first13=Montserrat |last14=Donaire-González |first14=David |last15=Gražulevičienė |first15=Regina |last16=Hernandez-Ferrer |first16=Carles |last17=Heude |first17=Barbara |last18=Mceachan |first18=Rosie |last19=Mon-Williams |first19=Mark |last20=Nieuwenhuijsen |first20=Mark |last21=Robinson |first21=Oliver |last22=Sakhi |first22=Amrit K. |last23=Sebastian-Galles |first23=Nuria |last24=Slama |first24=Remy |last25=Sunyer |first25=Jordi |last26=Tamayo-Uria |first26=Ibon |last27=Thomsen |first27=Cathrine |last28=Urquiza |first28=Jose |last29=Vafeiadi |first29=Marina |last30=Wright |first30=John |last31=Basagaña |first31=Xavier |last32=Vrijheid |first32=Martine |title=Early life multiple exposures and child cognitive function: A multi-centric birth cohort study in six European countries |journal=Environmental Pollution |date=1 September 2021 |volume=284 |pages=117404 |doi=10.1016/j.envpol.2021.117404 |pmid=34077897 |pmc=8287594 |language=en |issn=0269-7491}}</ref><ref name="10.1016/j.pharmthera.2020.107523"/> Prenatal exposure may also affect neurodevelopment.<ref>{{cite journal |last1=Volk |first1=Heather E. |last2=Perera |first2=Frederica |last3=Braun |first3=Joseph M. |last4=Kingsley |first4=Samantha L. |last5=Gray |first5=Kimberly |last6=Buckley |first6=Jessie |last7=Clougherty |first7=Jane E. |last8=Croen |first8=Lisa A. |last9=Eskenazi |first9=Brenda |last10=Herting |first10=Megan |last11=Just |first11=Allan C. |last12=Kloog |first12=Itai |last13=Margolis |first13=Amy |last14=McClure |first14=Leslie A. |last15=Miller |first15=Rachel |last16=Levine |first16=Sarah |last17=Wright |first17=Rosalind |title=Prenatal air pollution exposure and neurodevelopment: A review and blueprint for a harmonized approach within ECHO |journal=Environmental Research |date=1 May 2021 |volume=196 |pages=110320 |doi=10.1016/j.envres.2020.110320 |pmid=33098817 |pmc=8060371 |bibcode=2021ER....196k0320V |language=en |issn=0013-9351}}</ref><ref>{{cite journal |last1=Shang |first1=Li |last2=Yang |first2=Liren |last3=Yang |first3=Wenfang |last4=Huang |first4=Liyan |last5=Qi |first5=Cuifang |last6=Yang |first6=Zixuan |last7=Fu |first7=Zhuxuan |last8=Chung |first8=Mei Chun |title=Effects of prenatal exposure to NO<sub>2</sub> on children's neurodevelopment: a systematic review and meta-analysis |journal=Environmental Science and Pollution Research |date=1 July 2020 |volume=27 |issue=20 |pages=24786–24798 |doi=10.1007/s11356-020-08832-y |pmc=7329770 |pmid=32356052 |s2cid=216650267 |language=en |issn=1614-7499}}</ref> Studies show that air pollution is associated with a variety of developmental disabilities, oxidative stress, and neuro-inflammation and that it may contribute to Alzheimer's disease and Parkinson's disease.<ref name="10.1016/j.pharmthera.2020.107523">{{cite journal |last1=Costa |first1=Lucio G. |last2=Cole |first2=Toby B. |last3=Dao |first3=Khoi |last4=Chang |first4=Yu-Chi |last5=Coburn |first5=Jacki |last6=Garrick |first6=Jacqueline M. |title=Effects of air pollution on the nervous system and its possible role in neurodevelopmental and neurodegenerative disorders |journal=Pharmacology & Therapeutics |date=June 2020 |volume=210 |pages=107523 |doi=10.1016/j.pharmthera.2020.107523 |pmid=32165138 |pmc=7245732 |issn=1879-016X}}</ref>

Researchers at the University of Rochester Medical Center found that early exposure to air pollution causes the same changes in the brain as [[Medicine:Autism|autism]] and [[Medicine:Schizophrenia|schizophrenia]]. This study was published in the journal ''Environmental Health Perspectives'', in June 2014. It also showed that air pollution also affected [[Biology:Short-term memory|short-term memory]], learning ability, and [[Social:Impulsivity|impulsivity]]. Lead researcher Deborah Cory-Slechta said that: {{blockquote| When we looked closely at the [[Biology:Ventricular system|ventricles]], we could see that the [[Biology:White matter|white matter]] that normally surrounds them hadn't fully developed. It appears that [[Medicine:Inflammation|inflammation]] had damaged those brain cells and prevented that region of the brain from developing, and the ventricles simply expanded to fill the space. Our findings add to the growing body of evidence that air pollution may play a role in autism, as well as in other neurodevelopmental disorders.}}

Exposure to fine particulate matter can increase levels of [[Biology:Cytokine|cytokine]]s - neurotransmitters produced in response to infection and inflammation that are also associated with depression and suicide. Pollution has been associated with inflammation of the brain, which may disrupt mood regulation. According to a study of Washington DC's American University, heightened PM<sub>2.5</sub> levels are linked to more self-reported depressive symptoms, and increases in daily suicide rates.<ref>{{Cite web |last=Symons |first=Angela |date=2022-12-15 |title=Suicide rates rise as air quality worsens, study finds |url=https://www.euronews.com/green/2022/12/15/suicide-may-be-more-common-in-areas-worst-hit-by-air-pollution-new-study-reveals |access-date=2022-12-19 |website=euronews |language=en}}</ref>

In a study of mice, air pollution also has a larger negative impact on males than on females.<ref name="Allen Liu Pelkowski Palmer p.">{{cite journal |last1=Allen |first1=Joshua L. |last2=Liu |first2=Xiufang |last3=Pelkowski |first3=Sean |last4=Palmer |first4=Brian |last5=Conrad |first5=Katherine |last6=Oberdörster |first6=Günter |last7=Weston |first7=Douglas |last8=Mayer-Pröschel |first8=Margot |last9=Cory-Slechta |first9=Deborah A. |s2cid=6090961 |title=Early Postnatal Exposure to Ultrafine Particulate Matter Air Pollution: Persistent Ventriculomegaly, Neurochemical Disruption, and Glial Activation Preferentially in Male Mice |journal=Environmental Health Perspectives |volume=122 |issue=9 |pages=939–945 |date=5 June 2014 |issn=0091-6765 |doi=10.1289/ehp.1307984 |pmid=24901756 |pmc=4154219}}</ref><ref name="McEnaney-effects">{{cite news|last1=McEnaney |first1=Michael |title=Air pollution link discovered to autism, schizophrenia risks |url=http://www.techtimes.com/articles/8147/20140607/air-pollution-link-discovered-autism-schizophrenia-risks.htm |access-date=8 June 2014 |date=7 June 2014 |ref=Tech Times}}</ref><ref name="University of Rochester">{{cite news|title=New Evidence Links Air Pollution to Autism, Schizophrenia |url=http://www.urmc.rochester.edu/news/story/index.cfm?id=4100 |access-date=8 June 2014 |publisher=[[Organization:University of Rochester|University of Rochester]] Medical Center |date=6 June 2014}}</ref>

In 2015, experimental studies reported the detection of significant episodic (situational) cognitive impairment from impurities in indoor air breathed by test subjects who were not informed about changes in the air quality. Researchers at the [[Organization:Harvard University|Harvard University]] and SUNY Upstate Medical University and Syracuse University measured the cognitive performance of 24 participants in three different controlled laboratory atmospheres that simulated those found in "conventional" and "green" buildings, as well as green buildings with enhanced ventilation. Performance was evaluated objectively using the widely used Strategic Management Simulation software simulation tool, which is a well-validated assessment test for executive decision-making in an unconstrained situation allowing initiative and improvisation. Significant deficits were observed in the performance scores achieved in increasing concentrations of either [[Earth:Volatile organic compound|volatile organic compound]]s (VOCs) or carbon dioxide, while keeping other factors constant. The highest impurity levels reached are not uncommon in some classroom or office environments.<ref name=NYT>{{cite news |title=New Study Demonstrates Indoor Building Environment Has Significant, Positive Impact on Cognitive Function |work={{wipe|The New York Times}} |date=26 October 2015 |url=http://markets.on.nytimes.com/research/stocks/news/press_release.asp}}</ref><ref name=EHP>{{cite journal |last1=Allen |first1=Joseph G. |last2=MacNaughton |first2=Piers |last3=Satish |first3=Usha |last4=Santanam |first4=Suresh |last5=Vallarino |first5=Jose |last6=Spengler |first6=John D. |s2cid=12756582 |title=Associations of Cognitive Function Scores with Carbon Dioxide, Ventilation, and Volatile Organic Compound Exposures in Office Workers: A Controlled Exposure Study of Green and Conventional Office Environments |journal=Environmental Health Perspectives |year=2015 |volume=124 |issue=6 |doi=10.1289/ehp.1510037 |pmid=26502459 |pmc=4892924 |pages=805–12}}</ref> Higher PM<sub>2.5</sub> and {{CO2}} concentrations were shown to be associated with slower response times and reduced accuracy in tests.<ref>{{cite journal |last1=Cedeño Laurent |first1=Jose Guillermo |last2=MacNaughton |first2=Piers |last3=Jones |first3=Emily |last4=Young |first4=Anna S |last5=Bliss |first5=Maya |last6=Flanigan |first6=Skye |last7=Vallarino |first7=Jose |last8=Chen |first8=Ling Jyh |last9=Cao |first9=Xiaodong |last10=Allen |first10=Joseph G |title=Associations between acute exposures to PM2.5 and carbon dioxide indoors and cognitive function in office workers: a multicountry longitudinal prospective observational study |journal=Environmental Research Letters |date=1 September 2021 |volume=16 |issue=9 |pages=094047 |doi=10.1088/1748-9326/ac1bd8 |pmid=35330988 |pmc=8942432 |bibcode=2021ERL....16i4047C |s2cid=237462480 |language=en |issn=1748-9326}}</ref>

== Agricultural effects ==
Various studies have estimated the impacts of air pollution on agriculture, especially ozone. A 2020  study showed that ozone pollution in California may reduce yields of certain perennial crops such as table grapes by as much as 22% per year, translating into economic damages of more than $1 billion per year.<ref>{{Cite journal|display-authors=3 |last1=Hong |first1=Chaopeng |last2=Mueller |first2= Nathaniel D. |last3=Burney |first3=Jennifer A. |last4=Zhang |first4=Yang |last5=AghaKouchak |first5=Amir |last6=Moore |first6=Frances C. |last7=Qin |first7=Yue |last8=Tong |first8=Dan |last9=Davis |first9=Steven J. |date=2020 |title=Impacts of ozone and climate change on yields of perennial crops in California |url=https://www.nature.com/articles/s43016-020-0043-8 |journal=Nature Food |language=en |volume=1 |issue=3 |pages=166–172 |doi=10.1038/s43016-020-0043-8|s2cid=216425480 }}</ref> After air pollutants enter the agricultural environment, they not only directly affect agricultural production and quality, but also enter agricultural waters and soil.<ref>{{Cite journal |last1=Li |first1=Houjian |last2=Tang |first2=Mengqian |last3=Cao |first3=Andi |last4=Guo |first4=Lili |date=2022 |title=Assessing the relationship between air pollution, agricultural insurance, and agricultural green total factor productivity: evidence from China |url=https://link.springer.com/10.1007/s11356-022-21287-7 |journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=52 |pages=78381–78395 |doi=10.1007/s11356-022-21287-7 |pmid=35689771 |bibcode=2022ESPR...2978381L |s2cid=249551277 |issn=0944-1344}}</ref> The COVID-19 induced lockdown served as a natural experiment to expose the close links between air quality and surface greenness. In India, the lockdown induced improvement in air quality, enhanced surface greenness and photosynthetic activity, with the positive response of vegetation to reduce air pollution was dominant in croplands.<ref>{{Cite journal |last1=Kashyap |first1=Rahul |last2=Kuttippurath |first2=J. |last3=Patel |first3=V. K. |date=2023 |title=Improved air quality leads to enhanced vegetation growth during the COVID–19 lockdown in India |journal=Applied Geography |language=en |volume=151 |pages=102869 |doi=10.1016/j.apgeog.2022.102869 |pmid=36619606 |pmc=9805897 |bibcode=2023AppGe.15102869K |s2cid=255439854 |issn=0143-6228}}</ref> On the other hand, agriculture in its traditional form is one of the primary contributors to the emission of trace gases like atmospheric ammonia.<ref>{{Cite journal|display-authors=3 |last1=Kuttippurath |first1=J. |last2=Singh |first2=A. |last3=Dash |first3=S. P. |last4=Mallic |first4=N. |last5=Clerbaux |first5=C. |last6=Van Damme |first6=M. |last7=Clarisse |first7=L. |last8=Coheur |first8=P.-F. |last9=Raj |first9=S. |last10=Abbhishek |first10=K. |last11=Varikoden |first11=H.|date=2020 |title=Record high levels of atmospheric ammonia over India: Spatial and temporal analyses |url=https://www.sciencedirect.com/science/article/pii/S0048969720335063 |journal=Science of the Total Environment |language=en |volume=740 |pages=139986 |doi=10.1016/j.scitotenv.2020.139986 |pmid=32927535 |bibcode=2020ScTEn.740m9986K |s2cid=221722300 |issn=0048-9697}}</ref>

== Economic effects ==
Air pollution costs the [[Finance:World economy|world economy]] $5 trillion per year as a result of productivity losses and degraded quality of life, in a 2016 joint study by the [[Organization:World Bank|World Bank]] and the [[Organization:Institute for Health Metrics and Evaluation|Institute for Health Metrics and Evaluation]] (IHME) at the [[Organization:University of Washington|University of Washington]].<ref name="documents.worldbank.org">{{Cite book|url=http://documents.worldbank.org/curated/en/781521473177013155/pdf/108141-REVISED-Cost-of-PollutionWebCORRECTEDfile.pdf |title=The Cost of Air Pollution: Strengthening the Economic Case for Action |author1=[[Organization:World Bank|World Bank]] |author2=Institute for Health Metrics and Evaluation at University of Washington – Seattle |publisher=The World Bank |year=2016 |location=Washington, D.C. |page=xii |no-pp=y}}<!-- License: Creative Commons Attribution CC BY 3.0 IGO --></ref><ref name="commondreams.org">{{Cite news |url=https://www.commondreams.org/news/2016/09/08/making-case-clean-air-world-bank-says-pollution-cost-global-economy-5-trillion |title=Making Case for Clean Air, World Bank Says Pollution Cost Global Economy $5 Trillion |last=McCauley |first=Lauren |date=8 September 2016 |access-date=3 February 2018 |publisher=Common Dreams}}</ref><ref name="Fortune2018">{{Cite journal|last=<!--no byline--> |date=1 February 2018 |title=The Rising Cost of Smog |url=<!--paper copy, url not determined--> |journal=Fortune |page=15 |issn=0015-8259}}</ref> These productivity losses are caused by deaths due to diseases caused by air pollution. One out of ten deaths in 2013 was caused by diseases associated with air pollution and the problem is getting worse. The problem is even more acute in the developing world. "Children under age 5 in lower-income countries are more than 60 times as likely to die from exposure to air pollution as children in high-income countries."<ref name="documents.worldbank.org" /><ref name="commondreams.org"/> The report states that additional economic losses caused by air pollution, including health costs<ref>{{Cite web|url=http://www.unenvironment.org/news-and-stories/story/air-pollution-linked-huge-reduction-intelligence |title=Air pollution linked to "huge" reduction in intelligence |author=UN Environment |date=11 October 2018 |website=UN Environment |access-date=1 July 2019}}</ref> and the adverse effect on agricultural and other productivity were not calculated in the report, and thus the actual costs to the world economy are far higher than $5 trillion. A study published in 2022 found "a strong and significant connection between air pollution and construction site accidents" and that "a 10-ppb increase in NO₂ levels increases the likelihood of an accident by as much as 25 percent".<ref name="Lavy Rachkovski Yoresh 2022 p. ">{{cite report | last1=Lavy | first1=Victor | last2=Rachkovski | first2=Genia | last3=Yoresh | first3=Omry | url=https://www.nber.org/papers/w30715 | title=Heads Up: Does Air Pollution Cause Workplace Accidents? | publisher=National Bureau of Economic Research | publication-place=Cambridge, MA | year=2022 | doi=10.3386/w30715 | page=}}</ref>

== Other effects ==
Artificial air pollution may be detectable on Earth from distant vantage points such as other planetary systems via [[Astronomy:Technosignature#Atmospheric analysis|atmospheric SETI]]&nbsp;– including NO<sub>2</sub> pollution levels and with telescopic technology close to today. It may also be possible to detect extraterrestrial civilizations this way.<ref>{{cite news |first=Adam |last=Smith |title=Pollution on other planets could help us find aliens, Nasa says |url=https://www.independent.co.uk/life-style/gadgets-and-tech/alien-pollution-planets-nasa-b1801543.html |archive-url=https://web.archive.org/web/20210212170134/https://www.independent.co.uk/life-style/gadgets-and-tech/alien-pollution-planets-nasa-b1801543.html |archive-date=2021-02-12 |url-access=limited |url-status=live |access-date=6 March 2021 |work=The Independent |date=12 February 2021 |language=en}}</ref><ref>{{cite news |title=Can Alien Smog Lead Us to Extraterrestrial Civilizations? |url=https://www.wired.com/story/can-alien-smog-lead-us-to-extraterrestrial-civilizations/ |access-date=6 March 2021 |magazine=Wired |language=en-us}}</ref><ref>{{cite journal |last1=Kopparapu |first1=Ravi |last2=Arney |first2=Giada |last3=Haqq-Misra |first3=Jacob |last4=Lustig-Yaeger |first4=Jacob |last5=Villanueva |first5=Geronimo |title=Nitrogen Dioxide Pollution as a Signature of Extraterrestrial Technology |journal=[[Astronomy:The Astrophysical Journal|The Astrophysical Journal]] |date=22 February 2021 |volume=908 |issue=2 |pages=164 |doi=10.3847/1538-4357/abd7f7 |language=en |issn=1538-4357 |arxiv=2102.05027 |bibcode=2021ApJ...908..164K |s2cid=231855390 |doi-access=free }}</ref>

== Historical disasters ==
The world's worst short-term civilian pollution crisis was the 1984 Bhopal Disaster in India.<ref>{{cite news |publisher=Australian Broadcasting Corporation |first=Simi |last=Chakrabarti |url=http://www.abc.net.au/worldtoday/content/2004/s1257352.htm |title=20th anniversary of world's worst industrial disaster}}</ref> Leaked industrial vapours from the Union Carbide factory, belonging to Union Carbide, Inc., U.S.A. (later bought by [[Company:Dow Chemical Company|Dow Chemical Company]]), killed at least 3787 people and injured from 150,000 to 600,000. The United Kingdom suffered its worst air pollution event when the 4 December Great Smog of 1952 formed over London. In six days more than 4,000 died and more recent estimates put the figure at nearer 12,000.<ref name="EHP_112_1">{{cite journal |last1=Bell |first1=Michelle L. |first2=Devra L. |last2=Davis |first3=Tony |last3=Fletcher |s2cid=13045119 |date=January 2004 |title=A Retrospective Assessment of Mortality from the London Smog Episode of 1952: The Role of Influenza and Pollution |journal=Environ Health Perspect |volume=112 |issue=1 |pages=6–8 |doi=10.1289/ehp.6539 |pmid=14698923 |pmc=1241789}}</ref>

An [[Biology:Sverdlovsk anthrax leak|accidental leak of anthrax]] spores from a [[Biology:Biological warfare|biological warfare]] laboratory in the former USSR in 1979 near Yekaterinburg (formerly Sverdlovsk) is believed to have caused at least 64 deaths.<ref>{{cite journal |vauthors=Meselson M, Guillemin J, Hugh-Jones M |title=The Sverdlovsk anthrax outbreak of 1979 |journal=Science |volume=266 |issue=5188 |pages=1202–08 |date=November 1994 |pmid=7973702 |doi=10.1126/science.7973702 |url=http://www.anthrax.osd.mil/documents/library/Sverdlovsk.pdf |display-authors=0 |url-status=dead |archive-url=https://web.archive.org/web/20060921004004/http://www.anthrax.osd.mil/documents/library/Sverdlovsk.pdf |archive-date=21 September 2006 |bibcode=1994Sci...266.1202M}}</ref> The worst single incident of air pollution to occur in the US occurred in Donora, Pennsylvania, in late October 1948, when 20 people died and over 7,000 were injured.<ref>{{cite book|last=Davis |first=Devra |title=When Smoke Ran Like Water: Tales of Environmental Deception and the Battle Against Pollution |publisher=Basic Books |year=2002 |isbn=978-0-465-01521-4 |url-access=registration |url=https://archive.org/details/whensmokeranlike00davi}}</ref>

== Reduction and regulation ==
Global depletion of the surrounding air pollution will require valiant leadership, a surplus of combined resources from the international community, and extensive societal changes.<ref>{{cite journal |last1=Landrigan |first1=P |title=Air pollution and health |journal=Lancet |date=25 November 2016 |volume=2 |issue=1 |pages=E4–E5 |doi=10.1016/S2468-2667(16)30023-8|pmid=29249479 }}</ref> Pollution prevention seeks to prevent pollution such as air pollution and could include adjustments to industrial and business activities such as designing sustainable manufacturing processes (and the products' designs)<ref>{{cite journal |last1=Camahan |first1=James V. |last2=Thurston |first2=Deborah L. |title=Trade-off Modeling for Product and Manufacturing Process Design for the Environment |journal=[[Engineering:Journal of Industrial Ecology|Journal of Industrial Ecology]] |date=1998 |volume=2 |issue=1 |pages=79–92 |doi=10.1162/jiec.1998.2.1.79 |bibcode=1998JInEc...2...79C |s2cid=154730593 |language=en |issn=1530-9290}}</ref> and related legal regulations as well as efforts towards [[Earth:Renewable energy transition|renewable energy transition]]s.<ref>{{cite journal |last1=Jacobson |first1=Mark Z. |last2=von Krauland |first2=Anna-Katharina |last3=Coughlin |first3=Stephen J. |last4=Palmer |first4=Frances C. |last5=Smith |first5=Miles M. |title=Zero air pollution and zero carbon from all energy at low cost and without blackouts in variable weather throughout the U.S. with 100% wind-water-solar and storage |journal=Renewable Energy |date=1 January 2022 |volume=184 |pages=430–442 |doi=10.1016/j.renene.2021.11.067 |s2cid=244820608 |language=en |issn=0960-1481 |url=https://www.sciencedirect.com/science/article/abs/pii/S0960148121016499 |url-access=subscription}}</ref><ref>{{cite journal |last1=Gielen |first1=Dolf |last2=Boshell |first2=Francisco |last3=Saygin |first3=Deger |last4=Bazilian |first4=Morgan D. |last5=Wagner |first5=Nicholas |last6=Gorini |first6=Ricardo |title=The role of renewable energy in the global energy transformation |journal=Energy Strategy Reviews |date=1 April 2019 |volume=24 |pages=38–50 |doi=10.1016/j.esr.2019.01.006 |s2cid=135283552 |language=en |issn=2211-467X}}</ref>

Efforts to reduce particulate matter in the air may result in better health.<ref>{{cite journal |last1=Burns |first1=J |last2=Boogaard |first2=H |last3=Polus |first3=S |last4=Pfadenhauer |first4=LM |last5=Rohwer |first5=AC |last6=van-Erp |first6=AM |last7=Turley |first7=R |last8=Rehfeuss |first8=E |title=Interventions to Reduce Ambient Particulate Matter Air Pollution and Their Effect on Health |journal=Cochrane Database of Systematic Reviews |date=20 May 2019 |volume=2019 |issue=5 |pages=CD010919 |doi=10.1002/14651858.CD010919.pub2 |pmid=31106396 |pmc=6526394}}</ref>

The 9-Euro-Ticket scheme in Germany which allowed people to buy a monthly pass allowing use on all local and regional transport (trains, trams and busses) for 9 euro (€) for one month of unlimited travel saved 1.8 million tons of {{CO2}} emissions during its three-month implementation from June to August 2022.<ref>{{cite news |last= Connolly |first= Kate |date= 30 August 2022 |title= Germany's €9 train tickets scheme 'saved 1.8m tons of {{CO2}} emissions' |url= https://www.theguardian.com/world/2022/aug/30/germanys-9-train-tickets-scheme-saved-18m-tons-of-co2-emissions |work= The Guardian |access-date= 6 December 2022}}</ref>

=== Pollution control ===
[[File:Air pollution in Ghana 2.jpg|thumb|Burning of items polluting Jamestown environment in Accra, Ghana]]
Various pollution control technologies and strategies are available to reduce air pollution.<ref name="Fensterstock1971">{{cite journal |last1=Fensterstock | first1=J. C. |last2=Kurtzweg |first2=J. A. |last3=Ozolins | first3=G. |year=1971 |title=Reduction of Air Pollution Potential through Environmental Planning |journal=Journal of the Air Pollution Control Association |volume=21 |issue=7 |pages=395–399 |doi=10.1080/00022470.1971.10469547 |pmid=5148260}}</ref><ref name="Fensterstock1972">Fensterstock, Ketcham and Walsh, The Relationship of Land Use and Transportation Planning to Air Quality Management, Ed. George Hagevik, May 1972.</ref> At its most basic level, land-use planning is likely to involve zoning and transport infrastructure planning. In most developed countries, land-use planning is an important part of social policy, ensuring that land is used efficiently for the benefit of the wider economy and population, as well as to protect the environment.<ref>{{Cite web |title=The Importance of Development Plans/Land Use Policy for Development Control |url=http://www.oas.org/pgdm/document/bitc/papers/dthomas.htm |access-date=2022-06-17 |website=www.oas.org}}</ref> Stringent environmental regulations, effective control technologies and shift towards the renewable source of energy also helping countries like China and India to reduce their sulfur dioxide pollution.<ref>{{Cite journal |last1=Kuttippurath |first1=J. |last2=Patel |first2=V. K. |last3=Pathak |first3=M. |last4=Singh |first4=A. |date=2022 |title=Improvements in SO2 pollution in India: role of technology and environmental regulations|journal=Environmental Science and Pollution Research |language=en |volume=29 |issue=52 |pages=78637–78649 |doi=10.1007/s11356-022-21319-2 |pmid=35696063 |pmc=9189448 |bibcode=2022ESPR...2978637K |s2cid=249613744 |issn=1614-7499}}</ref>

[[Chemistry:Titanium dioxide|Titanium dioxide]] has been researched for its ability to reduce air pollution. [[Physics:Ultraviolet|Ultraviolet]] light will release free electrons from material, thereby creating free radicals, which break up VOCs and {{NOx}} gases. One form is [[Chemistry:Superhydrophilicity|superhydrophilic]].<ref>{{cite news |url=https://www.bbc.co.uk/news/science-environment-15694973 |first=Jason |last=Palmer |title='Smog-Eating' Material Breaking into the Big Time |date=12 November 2011 |work=BBC News}}</ref>

Pollution-eating [[Physics:Nanoparticle|nanoparticle]]s placed near a busy road were shown to absorb toxic emission from around 20 cars each day.<ref>{{cite news|url=https://www.bbc.com/news/science-environment-27425217 |title=Nanotechnology to gobble up pollution |work=BBC News |date=15 May 2014 |access-date=29 October 2014}}</ref>

=== Energy transition ===
Since a large share of air pollution is caused by combustion of fossil fuels such as coal and oil, the reduction of these fuels can reduce air pollution drastically. Most effective is the switch to clean power sources such as wind power, [[Engineering:Solar power|solar power]], hydro power which do not cause air pollution.<ref name="Jacobson" /> Efforts to reduce pollution from mobile sources includes expanding regulation to new sources (such as cruise and transport ships, farm equipment, and small gas-powered equipment such as [[Biology:String trimmer|string trimmer]]s, [[Biology:Chainsaw|chainsaw]]s, and snowmobiles), increased [[Physics:Fuel efficiency|fuel efficiency]] (such as through the use of [[Engineering:Hybrid vehicle|hybrid vehicle]]s), conversion to cleaner fuels, and conversion to [[Engineering:Electric vehicle|electric vehicle]]s.

A very effective means to reduce air pollution is the transition to [[Engineering:Renewable energy|renewable energy]]. According to a study published in Energy and Environmental Science in 2015 the switch to [[100% renewable energy|100% renewable energy]] in the United States would eliminate about 62,000 premature mortalities per year and about 42,000 in 2050, if no biomass were used. This would save about $600 billion in health costs a year due to reduced air pollution in 2050, or about 3.6% of the 2014 U.S. gross domestic product.<ref name="Jacobson">{{cite journal |last1=Jacobson |first1=Mark Z. |display-authors=0 |year=2015 |title=''100% clean and renewable wind, water, and sunlight (WWS) all-sector energy road maps for the 50 United States'' |journal=Energy and Environmental Science |volume=8 |issue=7 |pages= 2093–2117 |doi=10.1039/C5EE01283J}}</ref> Air quality improvement is a near-term benefit among the many societal benefits from [[Earth:Climate change mitigation|climate change mitigation]].

=== Alternatives to pollution ===
[[File:Within cities, make public transport more efficient and ban high-emission vehicles..svg|thumb|Support for a ban on high-emission vehicles in city centres in Europe, China and the US from respondents to the European Investment Bank Climate Survey]]
[[File:NET tram 201-03.jpg|thumb|Support, use and infrastructure-expansion of forms of public transport that do not cause air pollution may be a critical key alternative to pollution.]]

There are now practical alternatives to the principal causes of air pollution:
* Strategic substitution of air pollution sources in transport with lower-emission or, during the lifecycle, emission-free forms of [[Engineering:Public transport|public transport]]<ref>{{cite journal |last1=Landrigan |first1=Philip J. |title=Air pollution and health |journal=The Lancet Public Health |date=1 January 2017 |volume=2 |issue=1 |pages=e4–e5 |doi=10.1016/S2468-2667(16)30023-8 |pmid=29249479 |language=English |issn=2468-2667}}</ref><ref>{{cite journal |last1=Lyons |first1=T. J. |last2=Kenworthy |first2=J. R. |last3=Newman |first3=P. W. G. |title=Urban structure and air pollution |journal=Atmospheric Environment. Part B. Urban Atmosphere |date=1 January 1990 |volume=24 |issue=1 |pages=43–48 |doi=10.1016/0957-1272(90)90008-I |bibcode=1990AtmEB..24...43L |language=en |issn=0957-1272}}</ref> and bicycle use and infrastructure (as well as with remote work, reductions of work, relocations, and [[Philosophy:Localism (politics)|localizations]])
** [[Engineering:Phase-out of fossil fuel vehicles|Phase-out of fossil fuel vehicles]] is a critical component of a shift to [[Engineering:Sustainable transport|sustainable transport]]; however, similar infrastructure and design decisions like electric vehicles may be associated with similar pollution for production as well as mining and resource exploitation for large numbers of needed batteries as well as the energy for their recharging<ref>{{cite news |first=Karen |last=McVeigh |title='False choice': is deep-sea mining required for an electric vehicle revolution? |url=https://www.theguardian.com/environment/2021/sep/28/false-choice-is-deep-sea-mining-required-for-an-electric-vehicle-revolution |access-date=24 October 2021 |work={{wipe|The Guardian}} |date=28 September 2021 |language=en}}</ref><ref>{{cite news |first=Max |last=Opray |title=Nickel mining: the hidden environmental cost of electric cars |url=https://www.theguardian.com/sustainable-business/2017/aug/24/nickel-mining-hidden-environmental-cost-electric-cars-batteries |access-date=24 October 2021 |work={{wipe|The Guardian}} |date=24 August 2017 |language=en}}</ref>
* Areas downwind (over 20 miles) of major airports have more than double ''total particulate emissions in air'' than other areas, even when factoring in areas with frequent ship calls, and heavy freeway and city traffic like Los Angeles.<ref>{{cite web |url=https://cen.acs.org/articles/92/web/2014/05/Los-Angeles-Airport-Pollutes-City.html |title=Los Angeles Airport Pollutes City Air For Miles Downwind |access-date=13 December 2019 |publisher=Chemical and Engineering news |date=30 May 2014}}</ref> [[Biology:Aviation biofuel|Aviation biofuel]] mixed in with jetfuel at a 50/50 ratio can reduce jet derived cruise altitude particulate emissions by 50–70%, according to a [[Organization:NASA|NASA]] led 2017 study (however, this should imply ground level benefits to urban air pollution as well).<ref>{{cite web |url=http://www.flyingmag.com/nasa-confirms-biofuels-reduce-jet-emissions |title=NASA Confirms Biofuels Reduce Jet Emissions |website=Flyingmag.com |date=23 March 2017 |access-date=11 January 2018}}</ref>
* Ship propulsion and idling can be switched to much cleaner fuels like natural gas. (Ideally a [[Biology:Renewable natural gas|renewable source]] but not practical yet)
* Combustion of fossil fuels for space heating can be replaced by using ground source heat pumps and [[Physics:Seasonal thermal energy storage|seasonal thermal energy storage]].<ref>{{cite web |url=http://www.icax.co.uk/interseasonal_heat_transfer.html |title=Interseasonal Heat Transfer™ – Seasonal Heat Storage – GSHC – Renewable Heat & Renewable Cooling from ThermalBanks – Efficient Renewable Energy – Hybrid Renewable Energy Systems |website=Icax.co.uk |access-date=11 January 2018}}</ref>
* Electricity generated from the combustion of fossil fuels can be replaced by nuclear and renewable energy. Heating and home stoves, which contribute significantly to regional air pollution, can be replaced with a much cleaner fossil fuel, such as natural gas, or, preferably, renewables, in poor countries.<ref>{{Cite journal |last1=Ahuja |first1=Dilip |last2=Tatsutani |first2=Marika |date=2009-04-07 |title=Sustainable energy for developing countries |url=https://journals.openedition.org/sapiens/823 |journal=S.A.P.I.EN.S |volume=2 |language=fr |issue=1 |issn=1993-3800}}</ref><ref>{{Cite journal |last=Oyedepo |first=Sunday Olayinka |date=2012-07-23 |title=Energy and sustainable development in Nigeria: the way forward |journal=Energy, Sustainability and Society |volume=2 |issue=1 |pages=15 |doi=10.1186/2192-0567-2-15 |doi-access=free |s2cid=40436190 |issn=2192-0567}}</ref>
* Motor vehicles driven by fossil fuels, a key factor in urban air pollution, can be replaced by electric vehicles. Though lithium supply and cost is a limitation, there are alternatives. Herding more people into clean public transit such as electric trains can also help. Nevertheless, even in emission-free electric vehicles, rubber tires produce significant amounts of air pollution themselves, ranking as 13th worst pollutant in Los Angeles.<ref>{{cite web|url=http://sciencenetlinks.com/science-news/science-updates/road-rubber/ |title=Road Rubber |website=Sciencenetlinks.com Science Updates – Science NetLinks |access-date=11 January 2018}}</ref>
* Reducing travel in vehicles can curb pollution. After Stockholm reduced vehicle traffic in the central city with a congestion tax, nitrogen dioxide and PM<sub>10</sub> pollution declined, as did acute pediatric asthma attacks.<ref name=NBERMar2018>{{cite journal |last=Simeonova |first=Emilia |date=March 2018 |title=Congestion Pricing, Air Pollution and Children's Health |url=http://www.nber.org/papers/w24410 |website=National Bureau of Environmental Research |series=Working Paper Series |doi=10.3386/w24410}}</ref>
* [[Physics:Anaerobic digestion|Biodigesters]] can be utilized in poor nations where slash and burn is prevalent, turning a useless commodity into a source of income. The plants can be gathered and sold to a central authority that will break them down in a large modern biodigester, producing much needed energy to use.<ref>{{Cite web |last=Academy |first=Samphina |date=2022-04-16 |title=Impact Of Air Pollution On The Environment |url=https://samphina.com.ng/impact-air-pollution-environment/ |access-date=2022-06-18 |website=Samphina |language=en-US}}</ref>
* Induced humidity and ventilation both can greatly dampen air pollution in enclosed spaces, which was found to be relatively high inside subway lines due to braking and friction and relatively less ironically inside transit buses than lower sitting passenger automobiles or subways.<ref>{{cite web |url=https://www.chemistryworld.com/news/subway-air-pollution-damages-passenger-health/3007012.article |title=Subway air pollution damages passenger health |website=Chemistryworld.com |access-date=11 January 2018}}</ref>

=== Control devices ===
[[File:Debris netting.JPG|thumb|Tarps and netting are often used to reduce the amount of dust released from construction sites.]]
[[File:Atmospheric pollution.jpg|thumb|Air pollution from a car]]

The following items are commonly used as pollution control devices in industry and transportation. They can either destroy contaminants or remove them from an exhaust stream before it is emitted into the atmosphere.
{{Div col|colwidth=30em}}
* '''Particulate control'''
** Mechanical collectors ([[Physics:Cyclonic separation|dust cyclones]], multicyclones)
** [[Physics:Electrostatic precipitator|Electrostatic precipitator]]s: An electrostatic precipitator (ESP), or electrostatic air cleaner, is a particulate collection device that removes particles from a flowing gas (such as air), using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulates such as dust and smoke from the air stream.
** [[Chemistry:Dust collector#Types of baghouses|Baghouses]]: Designed to handle heavy dust loads, a dust collector consists of a blower, dust filter, a filter-cleaning system, and a dust receptacle or dust removal system (distinguished from air cleaners which utilize disposable filters to remove the dust).
** [[Physics:Wet scrubber|Particulate scrubbers]]: A wet scrubber is a form of pollution control technology. The term describes a variety of devices that use pollutants from a furnace flue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants.
* '''[[Engineering:Scrubber|Scrubber]]s'''
** [[Engineering:Baffle spray scrubber|Baffle spray scrubber]]
** [[Engineering:Cyclonic spray scrubber|Cyclonic spray scrubber]]
** [[Engineering:Ejector venturi scrubber|Ejector venturi scrubber]]
** [[Engineering:Mechanically aided scrubber|Mechanically aided scrubber]]
** [[Engineering:Spray tower|Spray tower]]
** [[Physics:Wet scrubber|Wet scrubber]]
* '''[[Chemistry:Nitrogen oxide|{{NOx}} control]]'''
** [[Engineering:LO-NOx burner|LO-NOx burner]]s
** [[Chemistry:Selective catalytic reduction|Selective catalytic reduction]] (SCR)
** Selective non-catalytic reduction (SNCR)
** [[Physics:Wet scrubber|NOx scrubbers]]
** [[Chemistry:Exhaust gas recirculation|Exhaust gas recirculation]]
** [[Chemistry:Catalytic converter|Catalytic converter]] (also for VOC control)
* '''[[Earth:Volatile organic compound|VOC abatement]]'''
** [[Chemistry:Adsorption|Adsorption systems]], using [[Physics:Activated carbon|activated carbon]], such as [[Chemistry:Fluidized bed concentrator|Fluidized Bed Concentrator]]
** [[Physics:Gas flare|Flares]]
** [[Engineering:Thermal oxidizer|Thermal oxidizer]]s
** [[Chemistry:Catalytic converter|Catalytic converter]]s
** [[Earth:Biofilter|Biofilter]]s
** [[Physics:Wet scrubber|Absorption (scrubbing)]]
** Cryogenic [[Physics:Condenser (heat transfer)|condensers]]
** [[Physics:Vapor recovery|Vapor recovery systems]]
* '''[[Chemistry:Acid gas|Acid gas]]/[[Chemistry:Sulfur dioxide|SO<sub>2</sub>]] control'''
** [[Physics:Wet scrubber|Wet scrubber]]s
** [[Engineering:Scrubber#Dry scrubbing|Dry scrubbers]]
** [[Physics:Flue-gas desulfurization|Flue-gas desulfurization]]
* '''[[Chemistry:Mercury (element)|Mercury]] control'''
** Sorbent injection technology
** Electro-catalytic oxidation (ECO)
** K-Fuel
* '''[[Chemistry:Dioxins and dioxin-like compounds|Dioxin]] and [[Chemistry:Furan|furan]] control'''
* '''Miscellaneous associated equipment'''
** Source capturing systems
** [[Engineering:Continuous emissions monitoring system|Continuous emissions monitoring system]]s (CEMS)
{{colend}}

=== Monitoring ===

=== Air quality modeling ===
{{Main|Earth:Air quality modeling}}
Numerical models either on a global scale using tools such as GCMs ([[Earth:General circulation model|general circulation model]]s coupled with a pollution module) or CTMs ([[Earth:Chemical transport model|Chemical transport model]]) can be used to simulate the levels of different pollutants in the atmosphere. These tools can have several types ([[Earth:Atmospheric model|Atmospheric model]]) and different uses. These models can be used in forecast mode which can help policy makers to decide on appropriate actions when an air pollution episode is detected. They can also be used for climate modeling including evolution of air quality in the future, for example the IPCC ([[Organization:Intergovernmental Panel on Climate Change|Intergovernmental Panel on Climate Change]]) provides climate simulations including air quality assessments in their reports (latest report accessible through their [https://www.ipcc.ch/ site]).

=== Regulations ===
{{Main|Earth:Air quality law}}
[[File:Cairo in smog.jpg|thumb|Smog in [[Place:Cairo|Cairo]]]]

In general, there are two types of air quality standards. The first class of standards (such as the U.S. [[Earth:National Ambient Air Quality Standards|National Ambient Air Quality Standards]] and E.U. Air Quality Directive<ref>{{Cite web |url=http://ec.europa.eu/environment/air/quality/legislation/directive.htm |archive-url=https://web.archive.org/web/20110511090225/http://ec.europa.eu/environment/air/quality/legislation/directive.htm |url-status=dead |archive-date=2011-05-11 |title=European Commission - Environment - Air - Air quality |date=11 May 2011 |author=European Commission}}</ref>) set maximum atmospheric concentrations for specific pollutants. Environmental agencies enact regulations which are intended to result in attainment of these target levels. The second class (such as the North American [[Earth:Air quality index|air quality index]]) take the form of a scale with various thresholds, which is used to communicate to the public the relative risk of outdoor activity. The scale may or may not distinguish between different pollutants.

==== Canada ====
In Canada, air pollution and associated health risks are measured with the [[Organization:Air Quality Health Index (Canada)|Air Quality Health Index]] (AQHI).<ref>{{Cite web |last=Canada |first=Environment and Climate Change |date=2007-09-10 |title=About the Air Quality Health Index |url=https://www.canada.ca/en/environment-climate-change/services/air-quality-health-index/about.html |access-date=2022-02-27 |website=Canada.ca}}</ref> It is a health protection tool used to make decisions to reduce short-term exposure to air pollution by adjusting activity levels during increased levels of air pollution.

The AQHI is a federal program jointly coordinated by [[Organization:Health Canada|Health Canada]] and Environment Canada. However, the AQHI program would not be possible without the commitment and support of the provinces, municipalities and [[Social:Non-governmental organization|NGOs]]. From air quality monitoring to health [[Risk communication|risk communication]] and community engagement, local partners are responsible for the vast majority of work related to AQHI implementation. The AQHI provides a number from 1 to 10+ to indicate the level of health risk associated with local air quality. Occasionally, when the amount of air pollution is abnormally high, the number may exceed 10. The AQHI provides a local air quality current value as well as a local air quality maximums forecast for today, tonight and tomorrow and provides associated health advice.

{|  style="margin:auto; background:Black; color:White;"
|- style="text-align:center;"
|  style="width:35px; height:35px; background:#9cf;"| '''1''' ||  style="text-align:center; width:35px; height:35px; background:#6cf;"| '''2''' ||  style="text-align:center; width:35px; height:35px; background:#0cf;"| '''3''' ||  style="text-align:center; width:35px; height:35px; background:#9cc;"| '''4''' ||  style="height:35px; height:35px; text-align:center; width:35px; text-align:center; width:35px; background:#999;"| '''5''' ||  style="text-align:center; width:35px; height:35px; background:#996;"| '''6''' ||  style="text-align:center; width:35px; height:35px; background:#960;"| '''7''' ||  style="text-align:center; width:35px; height:35px; background:#963;"| '''8''' ||  style="width:18px; width:35px; text-align:center; text-align:center; height:35px; background:#930;"| '''9'''||  style="width:18px; width:35px; text-align:center; text-align:center; height:35px; background:#600;"| '''10''' ||  style="text-align:center; width:35px; height:35px; background:#f00;"| '''+'''
|}
{|  style="margin:auto; background:white; color:black;"
|-
||'''Risk:'''|| Low '''(1–3)'''|| Moderate '''(4–6)'''|| High '''(7–10)''' || Very high '''(above 10)'''
|}

As it is now known that even low levels of air pollution can trigger discomfort for the sensitive population, the index has been developed as a continuum: The higher the number, the greater the health risk and need to take precautions. The index describes the level of health risk associated with this number as 'low', 'moderate', 'high' or 'very high', and suggests steps that can be taken to reduce exposure.<ref>{{cite web|url=http://www.ec.gc.ca/cas-aqhi/default.asp?lang=En&n=065BE995-1 |title=Environment Canada – Air Quality |website=Ec.gc.ca |date=10 September 2007 |access-date=11 November 2011}}</ref>

{| class="wikitable"
|-
! rowspan="2"|Health risk !! rowspan="2"|Air Quality Health Index !!colspan="2" style="text-align: center;"|Health messages<ref>{{cite web|url=http://www.ec.gc.ca/cas-aqhi/default.asp?lang=En&n=79A8041B-1 |title=Environment Canada – AQHI categories and explanations |website=Ec.gc.ca |date=16 April 2008 |access-date=11 November 2011}}</ref>
|-
! At risk population !! General population
|-
| '''Low''' || '''1–3'''|| '''Enjoy''' your usual outdoor activities.||'''Ideal''' air quality for outdoor activities
|-
| '''Moderate''' || '''4–6''' || '''Consider reducing''' or rescheduling strenuous activities outdoors if you are experiencing symptoms.||'''No need to modify''' your usual outdoor activities unless you experience symptoms such as coughing and throat irritation.
|-
| '''High''' || '''7–10''' || '''Reduce''' or reschedule strenuous activities outdoors. Children and the elderly should also take it easy.||'''Consider reducing''' or rescheduling strenuous activities outdoors if you experience symptoms such as coughing and throat irritation.
|-
| '''Very high''' || '''Above 10''' || '''Avoid''' strenuous activities outdoors. Children and the elderly should also avoid outdoor physical exertion and should stay indoors.||'''Reduce''' or reschedule strenuous activities outdoors, especially if you experience symptoms such as coughing and throat irritation.
|}

The measurement is based on the observed relationship of [[Chemistry:Nitrogen dioxide|nitrogen dioxide]] (NO<sub>2</sub>), ground-level ozone (O<sub>3</sub>) and particulates (PM<sub>2.5</sub>) with mortality, from an analysis of several Canadian cities. Significantly, all three of these pollutants can pose health risks, even at low levels of exposure, especially among those with pre-existing health problems.

When developing the AQHI, Health Canada's original analysis of health effects included five major air pollutants: particulates, [[Chemistry:Ozone|ozone]], and [[Chemistry:Nitrogen dioxide|nitrogen dioxide]] (NO<sub>2</sub>), as well as [[Chemistry:Sulfur dioxide|sulfur dioxide]] (SO<sub>2</sub>), and [[Chemistry:Carbon monoxide|carbon monoxide]] (CO). The latter two pollutants provided little information in predicting health effects and were removed from the AQHI formulation.

The AQHI does not measure the effects of odour, pollen, dust, heat or humidity.

==== Germany ====
[[Earth:TA Luft|TA Luft]] is the German air quality regulation.<ref>{{Cite web |title=German TA-Luft is guaranteed by us |url=https://www.centrotherm-cs.de/en/innovation/news-journal/detail/?cHash=2f8c3c73736a8bfee683c94544e0d805&tx_news_pi1%5Baction%5D=detail&tx_news_pi1%5Bcontroller%5D=News&tx_news_pi1%5Bnews%5D=9 |access-date=2022-02-27 |website=centrotherm clean solutions |language=en-US |archive-date=29 June 2022 |archive-url=https://web.archive.org/web/20220629162917/https://www.centrotherm-cs.de/en/innovation/news-journal/detail/?cHash=2f8c3c73736a8bfee683c94544e0d805&tx_news_pi1%5Baction%5D=detail&tx_news_pi1%5Bcontroller%5D=News&tx_news_pi1%5Bnews%5D=9 |url-status=dead }}</ref>

=== Governing urban air pollution ===
In Europe, Council Directive 96/62/EC on ambient air quality assessment and management provides a common strategy against which member states can "set objectives for ambient air quality in order to avoid, prevent or reduce harmful effects on human health and the environment&nbsp;... and improve air quality where it is unsatisfactory".<ref name=Europa1996>{{cite web|last=Europa |date=1996 |title=Summaries of EU legislation – Management and quality of ambient air |url=http://europa.eu/legislation_summaries/other/l28031a_en.htm |access-date=24 January 2015}}</ref>

In July 2008, in the case ''Dieter Janecek v. Freistaat Bayern'', the European Court of Justice ruled that under this directive<ref name=Europa1996/> citizens have the right to require national authorities to implement a short term action plan that aims to maintain or achieve compliance to air quality limit values.<ref name="CURIA 2008">{{cite web|author=European Court of Justice |first=CURIA |date=2008 |title=PRESS RELEASE No 58/08 Judgment of the Court of Justice in Case C-237/07 |url=http://curia.europa.eu/en/actu/communiques/cp08/aff/cp080058en.pdf |access-date=24 January 2015}}</ref><ref>Overview of relevant case law and critical state of air pollution protection in the EU: Winfried Huck, Jennifer Maaß, Saparya Sood, Tahar Benmaghnia, Alexander Schulte, Sarah Heß and Marc-Anthony Walter, The Right to Breathe Clean Air and Access to Justice - Legal State of Play in International, European and National Law (2021) in 8(22) International Institutions: Transnational Networks eJournal, available at: http://dx.doi.org/10.2139/ssrn.3808572</ref>

This important case law appears to confirm the role of the EC as centralised regulator to European nation-states as regards air pollution control. It places a supranational legal obligation on the UK to protect its citizens from dangerous levels of air pollution, furthermore superseding national interests with those of the citizen.

In 2010, the European Commission (EC) threatened the UK with legal action against the successive breaching of PM<sub>10</sub> limit values.<ref>{{cite web|author=European Commission |title=Air quality: Commission sends final warning to UK over levels of fine particle pollution |url=http://ec.europa.eu/unitedkingdom/press/press_releases/2010/pr1055_en.htm |access-date=7 April 2011 |archive-url=https://web.archive.org/web/20110511090215/http://ec.europa.eu/unitedkingdom/press/press_releases/2010/pr1055_en.htm |archive-date=11 May 2011 |url-status=dead}}</ref> The UK government has identified that if fines are imposed, they could cost the nation upwards of £300 million per year.<ref name="HoC Air Quality Report 2010">{{cite web|author=House of Commons Environmental Audit Committee |date=2010 |title=Environmental Audit Committee – Fifth Report Air Quality |url=https://publications.parliament.uk/pa/cm200910/cmselect/cmenvaud/229/22902.htm |access-date=24 January 2015}}</ref>

In March 2011, the Greater London Built-up Area remained the only UK region in breach of the EC's limit values, and was given three months to implement an emergency action plan aimed at meeting the EU Air Quality Directive.<ref name="Guardian2011">{{cite news|last=Mulholland |first=Hélène |title=Britain fends off threat of £300m fine over London air pollution |url=https://www.theguardian.com/environment/2011/mar/11/britain-300m-fine-london-air-pollution |access-date=24 January 2015 |newspaper={{wipe|The Guardian}} |date=11 March 2011}}</ref> The City of London has dangerous levels of PM<sub>10</sub> concentrations, estimated to cause 3000 deaths per year within the city.<ref>{{cite web|author=London Assembly Environment Committee (2009) |title=Every Breath You Take |url=https://www.london.gov.uk/sites/default/files/FINAL%20AIR%20QUALITY%20REPORT.pdf |access-date=22 February 2015 |url-status=dead |archive-url=https://web.archive.org/web/20150222163223/https://www.london.gov.uk/sites/default/files/FINAL%20AIR%20QUALITY%20REPORT.pdf |archive-date=22 February 2015}}</ref> As well as the threat of EU fines, in 2010 it was threatened with legal action for scrapping the western congestion charge zone, which is claimed to have led to an increase in air pollution levels.<ref>{{cite news|author=BBC |title=Threat to sue over London congestion charge scrapping |url=https://www.bbc.co.uk/news/uk-england-london-11928005 |access-date=24 January 2015 |work=BBC News |date=6 December 2010}}</ref>

In response to these charges, mayor of London Boris Johnson has criticised the current need for European cities to communicate with Europe through their nation state's [[Earth:Central government|central government]], arguing that in future "A great city like London" should be permitted to bypass its government and deal directly with the European Commission regarding its air quality action plan.<ref name="Guardian2011"/>

This can be interpreted as recognition that cities can transcend the traditional national government organisational hierarchy and develop solutions to air pollution using global governance networks, for example through transnational relations. Transnational relations include but are not exclusive to national governments and intergovernmental organisations,<ref name="Kappen">{{cite book|last=Risse-Kappen |first=T. |title=Bringing transnational relations back in: non-state actors, domestic structures, and international institutions |year=1995 |publisher={{wipe|Cambridge University Press}} |location=Cambridge |pages=3–34}}</ref> allowing sub-national actors including cities and regions to partake in air pollution control as independent actors.

Global city partnerships can be built into networks, for example the [[Organization:C40 Cities Climate Leadership Group|C40 Cities Climate Leadership Group]], of which London is a member. The C40 is a public 'non-state' network of the world's leading cities that aims to curb their greenhouse emissions.<ref name="pattberg">{{cite journal|last1=Pattberg |first1=P. |last2=Stripple |first2=J. |s2cid=62890754 |title=Beyond the public and private divide: remapping transnational climate governance in the 21st century |journal=International Environmental Agreements: Politics, Law and Economics |year=2008 |volume=8 |issue=4 |pages=367–388 |doi=10.1007/s10784-008-9085-3 |bibcode=2008IEAPL...8..367P |doi-access=free}}</ref> The C40 has been identified as 'governance from the middle' and is an alternative to intergovernmental policy.<ref>{{cite journal|last=Roman |first=M. |title=Governing from the middle: the C40 Cities Leadership Group |journal=Corporate Governance |year=2010 |volume=10 |issue=1 |pages=73–84 |doi=10.1108/14720701011021120}}</ref> It has the potential to improve urban air quality as participating cities "exchange information, learn from best practices and consequently mitigate carbon dioxide emissions independently from national government decisions".<ref name="pattberg"/> A criticism of the C40 network is that its exclusive nature limits influence to participating cities and risks drawing resources away from less powerful city and regional actors.

== Hotspots ==
{{Main|Physics:Toxic hotspot}}

Air pollution hotspots are areas where air pollution emissions expose individuals to increased negative health effects.<ref>{{cite web|title=Air pollution hot spot |url=http://www.greenfacts.org/glossary/abc/air-pollution-hot-spot.htm |access-date=24 April 2014}}</ref> They are particularly common in highly populated, urban areas, where there may be a combination of stationary sources (e.g. industrial facilities) and mobile sources (e.g. cars and trucks) of pollution. Emissions from these sources can cause [[Medicine:Respiratory disease|respiratory disease]], childhood [[Medicine:Asthma|asthma]],<ref name=":1" /> [[Medicine:Cancer|cancer]], and other health problems. Fine particulate matter such as [[Earth:Diesel exhaust|diesel soot]], which contributes to more than 3.2 million premature deaths around the world each year, is a significant problem. It is very small and can lodge itself within the lungs and enter the bloodstream. Diesel soot is concentrated in densely populated areas, and one in six people in the U.S. live near a diesel pollution hot spot.<ref>{{cite web|last=Pettit |first=David |title=Global Toll of Air Pollution: Over 3 Million Deaths Each Year |publisher=Switchboard NRDC |url=http://switchboard.nrdc.org/blogs/dpettit/global_toll_of_air_pollution_o.html |date=14 December 2014 |url-status=dead |archive-url=https://web.archive.org/web/20140508061609/http://switchboard.nrdc.org/blogs/dpettit/global_toll_of_air_pollution_o.html |archive-date=8 May 2014}}</ref>

{{ external media
| width  = 220px
| video1 = [https://airvisual.com/earth ''AirVisual Earth''] – realtime map of global wind and air pollution<ref>{{cite magazine|url=https://www.science.org/content/article/watch-air-pollution-flow-across-planet-real-time |title=Watch air pollution flow across the planet in real time |magazine=Science Magazine News |date=28 November 2016}}</ref>
}}

While air pollution hotspots affect a variety of populations, some groups are more likely to be located in hotspots. Previous studies have shown disparities in exposure to pollution by race and/or income. [[Hazard]]ous land uses (toxic storage and disposal facilities, manufacturing facilities, major roadways) tend to be located where property values and income levels are low. Low socioeconomic status can be a proxy for other kinds of [[Social:Social vulnerability|social vulnerability]], including race, a lack of ability to influence regulation and a lack of ability to move to neighborhoods with less environmental pollution. These communities bear a disproportionate burden of environmental pollution and are more likely to face health risks such as [[Medicine:Cancer|cancer]] or [[Medicine:Asthma|asthma]].<ref name="Drury">{{cite journal |last1=Drury |first1=Richard |last2=Belliveau |first2=Michael |last3=Kuhn |first3=J. Scott |last4=Shipra |first4=Bansal |title=Pollution Trading and Environmental Justice: Los Angeles' Failed Experiment in Air Pollution Policy |journal=Duke Environmental Law & Policy Forum |date=Spring 1999 |volume=9 |issue=231}}</ref>

Studies show that patterns in race and income disparities not only indicate a higher exposure to pollution but also higher risk of adverse health outcomes.<ref name="Morello-Frosch 2011">{{cite journal |last1=Morello-Frosch |first1=Rachel |last2=Zuk |first2=Miriam |last3=Jerrett |first3=Michael |last4=Shamasunder |first4=Bhavna |last5=Kyle |first5=Amy D. |title=Understanding the Cumulative Impacts of Inequalities in Environmental Health: Implications for Policy |journal=Health Affairs |year=2011 |volume=30 |issue=5 |doi=10.1377/hlthaff.2011.0153 |pmid=21555471 |pages=879–87 |doi-access=free}}</ref> Communities characterized by low socioeconomic status and racial minorities can be more vulnerable to cumulative adverse health impacts resulting from elevated exposure to pollutants than more privileged communities.<ref name="Morello-Frosch 2011"/> Blacks and Latinos generally face more pollution than Whites and Asians, and low-income communities bear a higher burden of risk than affluent ones.<ref name="Drury"/> Racial discrepancies are particularly distinct in suburban areas of the Southern United States and metropolitan areas of the Midwestern and Western United States.<ref>{{cite journal |title=Racial and Socioeocnomic Disparities in Residential Proximity |journal=American Journal of Public Health |year=2009 |volume=99 |issue=3 |doi=10.2105/ajph.2007.131383 |pages=S649–56 |pmid=19890171 |pmc=2774179 |last1=Mohai |first1=P. |last2=Lantz |first2=P.M. |last3=Morenoff |first3=J. |last4=House |first4=J.S. |last5=Mero |first5=R.P.}}</ref> Residents in public housing, who are generally low-income and cannot move to healthier neighborhoods, are highly affected by nearby [[Chemistry:Refinery|refineries]] and chemical plants.<ref>{{cite journal|last=Lerner |first=Steve |journal=Port Arthur, Texas: Public Housing Residents Breathe Contaminated Air from Nearby Refineries and Chemical Plants |title=Sacrifice Zones: The Front Lines of Toxic Chemical Exposure in the United States |publisher=MIT Press |year=2010}}</ref>

== Cities ==
[[File:Global air pollution map.png|thumb|upright=1.35|Nitrogen dioxide concentrations as measured from satellite 2002–2004]]
Air pollution is usually concentrated in densely populated metropolitan areas, especially in developing countries where cities are experiencing rapid growth and environmental regulations are relatively lax or nonexistent. Urbanization leads to a rapid rise in premature [[Mortality rate|mortality]] due to anthropogenic air pollution in fast-growing tropical cities.<ref>{{Cite journal |last1=Vohra |first1=Karn |last2=Marais |first2=Eloise A. |last3=Bloss |first3=William J. |last4=Schwartz |first4=Joel |last5=Mickley |first5=Loretta J. |last6=Van Damme |first6=Martin |last7=Clarisse |first7=Lieven |last8=Coheur |first8=Pierre-F. |date=2022-04-08 |title=Rapid rise in premature mortality due to anthropogenic air pollution in fast-growing tropical cities from 2005 to 2018 |journal=Science Advances |language=en |volume=8 |issue=14 |pages=eabm4435 |doi=10.1126/sciadv.abm4435 |pmid=35394832 |pmc=8993110 |bibcode=2022SciA....8M4435V |issn=2375-2548}}</ref> However, even populated areas in developed countries attain unhealthy levels of pollution, with Los Angeles and Rome being two examples.<ref>{{Cite journal |pmc=1757645 |jstor=27730990 |pages=605–10 |last1=Michelozzi |first1=P. |last2=Forastiere |first2=F. |last3=Fusco |first3=D. |last4=Perucci |first4=C. A. |last5=Ostro |first5=B. |last6=Ancona |first6=C. |last7=Pallotti |first7=G. |title=Air Pollution and Daily Mortality in Rome, Italy |volume=55 |issue=9 |journal=Occupational and Environmental Medicine |year=1998 |pmid=9861182 |doi=10.1136/oem.55.9.605}}</ref> Between 2002 and 2011 the incidence of lung cancer in Beijing near doubled. While smoking remains the leading cause of lung cancer in China, the number of smokers is falling while lung cancer rates are rising .<ref>The Daily Telegraph 8 January 2014 'Air pollution killing up to 500,000 Chinese each year, admits former health minister'.</ref>
{| class="wikitable"
|+<ref>{{Cite web|title=World's Most Polluted Cities in 2020 - PM2.5 Ranking {{!}} AirVisual |url=https://www.iqair.com/us/world-most-polluted-cities |access-date=2022-02-01 |website=www.iqair.com |language=en-us}}</ref>
!World's Most Polluted Cities 2020
!2020 Average
!2019 Average
|-
|Hotan, China
|110.2
|110.1
|-
|Ghaziabad, India
|106.6
|110.2
|-
|Bulandshahr, India
|98.4
|89.4
|-
|Bisrakh Jalalpur, India
|96.0
| -
|-
|Bhiwadi, India
|95.5
|83.4
|}
Tehran was declared the most polluted city in the world on May 24, 2022.<ref>{{Cite web |title=World Air Quality Index (AQI) Ranking {{!}} IQAir |url=https://www.iqair.com/world-air-quality-ranking |access-date=2022-05-24 |website=www.iqair.com |language=en}}</ref>

== Projections ==
In a 2019 projection, by 2030 half of the world's pollution emissions could be generated by Africa.<ref>{{cite web|url=https://www.lemonde.fr/afrique/article/2019/11/29/en-afrique-de-l-ouest-une-pollution-mortelle-mais-d-ampleur-inconnue_6021103_3212.html |language=fr |title=En Afrique de l'Ouest, une pollution mortelle mais d'ampleur inconnue |trans-title=In West Africa, deadly pollution but of unknown magnitude |date=29 November 2019 |first=Mariama |last=Darame |website=Le Monde}}</ref> Potential contributors to such an outcome include increased burning activities (such as the burning of open waste), traffic, agri-food and chemical industries, sand dust from the Sahara, and overall population growth.

In a 2012 study, by 2050 outdoor air pollution (particulate matter and ground-level ozone) is projected to become the top cause of environmentally related deaths worldwide.<ref>{{cite web |url=https://www.oecd.org/environment/indicators-modelling-outlooks/49928853.pdf |title=Environmental Ooutlook to 2050 - OECD |date=1 March 2012 |author=Organisation for Economic Co-operation and Development |website=[[Organization:OECD|OECD]]}}</ref>

== See also ==
{{Div col|small=yes}}

'''Source'''
* Beehive burner
* [[Earth:Bottom ash|Bottom ash]]
* [[Chemistry:Concrete#Concrete %E2%80%93 health and safety|Concrete]]
* Diwali-related air pollution
* [[Physics:Flue-gas emissions from fossil-fuel combustion|Flue-gas emissions from fossil-fuel combustion]]
* Health impacts of sawdust
* [[Biology:Joss paper|Joss paper]]
* Metal working
* Mining
* [[Earth:Non-exhaust emissions|Non-exhaust emissions]]
* [[Engineering:Power tool|Power tool]]
* Rubber pollution
* [[Chemistry:Slag|Slag]]
* [[Engineering:Smelting|Smelting]]
* [[Engineering:Tire fire|Tire fire]]
* [[Chemistry:Welding|Welding]]
* [[Chemistry:Wood ash|Wood ash]]

'''Measurement'''
* [[Earth:Air pollutant concentrations|Air pollutant concentrations]]
* [[Earth:Air pollution measurement|Air pollution measurement]]
* [[Earth:Organic molecular tracers|Organic molecular tracers]]
* Intake fraction
* [[Engineering:Particulate matter sampler|Particulate matter sampler]]

'''Others'''
* [[Earth:Air stagnation|Air stagnation]]
* ASEAN Agreement on Transboundary Haze Pollution
* [[Earth:Asian brown cloud|Asian brown cloud]]
* [[Earth:Atmospheric chemistry|Atmospheric chemistry]]
* [[Software:BenMAP|BenMAP]]
* Best Available Control Technology
* [[Earth:Critical load|Critical load]]
* [[Earth:Emission standard|Emission standard]]
* Emissions & Generation Resource Integrated Database
* Environmental agreement
* Environmental racism
* [[Philosophy:Exposome|Exposome]]
* [[Earth:Global Atmosphere Watch|Global Atmosphere Watch]]
* [[Earth:Global dimming|Global dimming]]
* Great Smog of London
* [[Earth:Haze|Haze]]
* Health Effects Institute (HEI)
* [[Biology:Indicator value|Indicator value]]
* [[Organization:International Agency for Research on Cancer|International Agency for Research on Cancer]]
* International Day of Clean Air for Blue Skies
* [[Chemistry:Kyoto Protocol|Kyoto Protocol]]
* Light water reactor sustainability
* List of smogs by death toll
* Lowest Achievable Emissions Rate
* [[Astronomy:NASA Clean Air Study|NASA Clean Air Study]]
* NIEHS
* [[Social:Polluter pays principle|Polluter pays principle]]
* Regulation of greenhouse gases under the Clean Air Act
* Silicosis#Prevention
{{Div col end}}

== References ==
{{Reflist}}

== Further reading ==
{{Library resources box |by=no |onlinebooks=no |others=yes lcheading=Air – Pollution}}
* {{cite book |last1=Brimblecombe|first1=Peter |title=The Big Smoke: A History of Air Pollution in London Since Medieval Times |date=1987 |publisher=Routledge |isbn=9781136703294}}
* {{cite book |last1=Brimblecombe |first1=Peter |editor1-last=Singh |editor1-first=H.B. |title=Composition, chemistry, and climate of the atmosphere |date=1995 |publisher=John Wiley & Sons |location=New York |isbn=9780471285144 |url=https://www.worldcat.org/oclc/43084000 |chapter=1: History of air pollution|pages=1–18|oclc=43084000 }}
* {{cite journal |last1=Brimblecombe |first1=Peter|last2=Makra |first2=László |year=2005 |title=Selections from the history of environmental pollution, with special attention to air pollution. Part 2*: From medieval times to the 19th century |journal=International Journal of Environment and Pollution |volume=23 |issue=4 |pages=351–67 |doi=10.1504/ijep.2005.007599 |}}
* Cherni, Judith A. ''Economic Growth versus the Environment: The Politics of Wealth, Health and Air Pollution'' (2002) [https://web.archive.org/web/20150213161206/https://www.questia.com/library/102251606/economic-growth-versus-the-environment-the-politics online]
* Corton, Christine L. ''London Fog: The Biography'' (2015)
* Currie, Donya. "WHO: Air Pollution a Continuing Health Threat in World's Cities", ''The Nation's Health'' (February 2012) 42#1 [https://web.archive.org/web/20150402122918/https://www.questia.com/article/1G1-280406027/who-air-pollution-a-continuing-health-threat-in-world-s online]
* Dewey, Scott Hamilton. ''Don't Breathe the Air: Air Pollution and US Environmental Politics, 1945–1970'' (Texas A & M University Press, 2000)
* Gonzalez, George A. ''The politics of air pollution: Urban growth, ecological modernization, and symbolic inclusion'' (SUNY Press, 2012)
* {{cite journal |last1=Grinder |first1=Robert Dale |year=1978 |title=From Insurgency to Efficiency: The Smoke Abatement Campaign in Pittsburgh before World War I. |journal=Western Pennsylvania Historical Magazine |volume=61 |issue=3 |pages=187–202}}
* Grinder, Robert Dale. "The Battle for Clean Air: The Smoke Problem in Post-Civil War America" in Martin V. Melosi, ed., ''Pollution & Reform in American Cities, 1870–1930'' (1980), pp.&nbsp;83–103.
* {{cite journal | last1=Kumar | first1=Prashant | last2=Pirjola | first2=Liisa | last3=Ketzel | first3=Matthias | last4=Harrison | first4=Roy M. | title=Nanoparticle emissions from 11 non-vehicle exhaust sources – A review | journal=Atmospheric Environment | publisher=Elsevier BV | volume=67 | year=2013 | issn=1352-2310 | doi=10.1016/j.atmosenv.2012.11.011 | pages=252–277 | bibcode=2013AtmEn..67..252K | url=https://openresearch.surrey.ac.uk/view/pdfCoverPage?instCode=44SUR_INST&filePid=13140580700002346&download=true}}
* {{cite book |last1=Lundqvist |first1=Lennart J. |title=The Hare and the Tortoise: Clean Air Policy in the US and Sweden |date=1980 |publisher=University of Michigan Press |location=Ann Arbor, MI |isbn=9780472093106}}
* Mingle, Jonathan, "Our Lethal Air" [review of Gary Fuller, ''The Invisible Killer...''; Beth Gardiner, ''Choked...''; Tim Smedley, ''Clearing the Air...''; U.S. Environmental Protection Agency, ''Integrated Science Assessment for Particulate Matter (External Review Draft, 2018)''; and Chartered Clean Air Scientific Advisory Committee, ''Letter to EPA Administrator on the EPA's Integrated Science Assessment for Particulate Matter, 11 April 2019''], ''The New York Review of Books'', vol. LXVI, no. 14 (26 September 2019), pp.&nbsp;64–66, 68. "Today, 91 percent of people worldwide live in areas where air pollution levels exceed the World Health Organization's recommended limits.&nbsp;... [T]here is no safe level of exposure to fine particulate matter.&nbsp;... Most of these fine particles are a by-product of&nbsp;... burning&nbsp;... [[Earth:Coal|coal]], [[Chemistry:Gasoline|gasoline]], [[Chemistry:Diesel fuel|diesel]], [[Biology:Wood|wood]], trash&nbsp;... These particles can get past the defenses of our upper airways to penetrate deep into our [[Medicine:Lung|lung]]s and reach the alveoli&nbsp;... From there, they cross into the bloodstream and spread throughout the body. They can travel through the [[Medicine:Nose|nose]], up the [[Biology:Olfactory nerve|olfactory nerve]], and lodge&nbsp;... in the [[Biology:Brain|brain]]. They can form deposits on the lining of arteries, constricting blood vessels and raising the likelihood of&nbsp;... [[Medicine:Stroke|stroke]]s and heart attacks. [T]hey exacerbate respiratory illnesses like [[Medicine:Asthma|asthma]] and [[Medicine:Chronic obstructive pulmonary disease|chronic obstructive pulmonary disease]]&nbsp;... There's&nbsp;... evidence linking air pollution exposure to an increased risk of [[Medicine:Alzheimer's disease|Alzheimer's]] and other forms of [[Medicine:Dementia|dementia]]." (p.&nbsp;64.)
* Mosley, Stephen. The chimney of the world: a history of smoke pollution in Victorian and Edwardian Manchester. Routledge, 2013.
* Schreurs, Miranda A. ''Environmental Politics in Japan, Germany, and the United States'' (Cambridge University Press, 2002) [https://web.archive.org/web/20141003113536/https://www.questia.com/library/108673238/environmental-politics-in-japan-germany-and-the online]
* Thorsheim, Peter. ''Inventing Pollution: Coal, Smoke, and Culture in Britain since 1800'' (2009)

== External links ==
{{Commons}}
{{Wikivoyage|3=travel information}}

* [https://www.who.int/news-room/fact-sheets/detail/ambient-(outdoor)-air-quality-and-health WHO fact sheet on outdoor air pollution]
* [https://www.nrdc.org/stories/air-pollution-everything-you-need-know Air Pollution: Everything You Need to Know] Guide by the Natural Resources Defense Council (NRDC)
* [http://aqicn.org/map/world/ Global real-time air quality index map]
* [https://www.airnow.gov/aqi/aqi-basics/ Air Quality Index (AQI) Basics]
* [https://www.airnow.gov/aqi/aqi-calculator/ AQI Calculator] AQI to Concentration and Concentration to AQI for five pollutants
* [https://www.unep.org/explore-topics/resource-efficiency/what-we-do/cities/urban-environmental-planning UNEP Urban environmental planning]
* [https://ec.europa.eu/environment/air/quality/index.htm European Commission > Environment > Air > Air Quality]
* [https://web.archive.org/web/20110927100158/http://www.who.int/phe/health_topics/outdoorair/databases/en/index.html Database: outdoor air pollution in cities] from the World Health Organization
* [https://www.gov.uk/government/publications/comeap-mortality-effects-of-long-term-exposure-to-particulate-air-pollution-in-the-uk The Mortality Effects of Long-Term Exposure to Particulate Air Pollution in the United Kingdom], UK Committee on the Medical Effects of Air Pollution, 2010.
* [https://www.epa.gov/haps/ Hazardous air pollutants] | [https://www.epa.gov/haps/what-are-hazardous-air-pollutants What are hazardous pollutants] at EPA.gov

{{Pollution}}
{{Environmental science}}
{{Natural resources}}

{{DEFAULTSORT:Air Pollution}}
[[Category:Air pollution| ]]

{{Sourceattribution|Air pollution}}