View source for Chemistry:Hydrogen sulfide

{{short description|Poisonous, corrosive and flammable gas}}
{{Chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 477313464
| Name = 
| ImageFile = 
| ImageFile1 = Hydrogen-sulfide-2D-dimensions.svg
| ImageFile1_Ref = {{chemboximage|correct|??}}
| ImageSize1 = 170
| ImageName1 = Skeletal formula of hydrogen sulfide with two dimensions
| ImageFileL1 = Hydrogen-sulfide-3D-balls.png
| ImageNameL1 = Ball-and-stick model of hydrogen sulfide
| ImageFileR1 = Hydrogen-sulfide-3D-vdW.svg
| ImageFileR1_Ref = {{chemboximage|correct|??}}
| ImageNameR1 = Spacefill model of hydrogen sulfide
| ImageCaptionR1 = {{legend|yellow|Sulfur, S}}{{legend|white|Hydrogen, H}}
| SystematicName = Hydrogen sulfide<ref name="pubchem">{{cite web|title = Hydrogen Sulfide - PubChem Public Chemical Database|url = https://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=402&loc=ec_rcs|work = The PubChem Project|location = USA|publisher = National Center for Biotechnology Information}}</ref>
| OtherNames = {{ubl|Dihydrogen monosulfide|Sour gas|Dihydrogen sulfide|Sewer gas|Egg gas|Sulfane|Sulfurated hydrogen|Sulfureted hydrogen|Sulfuretted hydrogen|Sulfur hydride|Hydrosulfuric acid|Hydrothionic acid|Thiohydroxic acid|Sulfhydric acid}}
| IUPACName = 
| Section1 = {{Chembox Identifiers
| CASNo = 7783-06-4
| CASNo_Ref = {{cascite|correct|CAS}}
| PubChem = 402
| ChemSpiderID = 391
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| UNII = YY9FVM7NSN
| UNII_Ref = {{fdacite|correct|FDA}}
| EINECS = 231-977-3
| UNNumber = 1053
| KEGG = C00283
| KEGG_Ref = {{keggcite|correct|kegg}}
| MeSHName = Hydrogen+sulfide
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 16136
| ChEMBL = 1200739
| ChEMBL_Ref = {{ebicite|changed|EBI}}
| RTECS = MX1225000
| Beilstein = 3535004
| Gmelin = 303
| 3DMet = B01206
| SMILES = S
| StdInChI = 1S/H2S/h1H2
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| InChI = 1/H2S/h1H2
| StdInChIKey = RWSOTUBLDIXVET-UHFFFAOYSA-N
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| InChIKey = RWSOTUBLDIXVET-UHFFFAOYAJ
}}
| Section2 = {{Chembox Properties
| H=2 | S=1
| Appearance = Colorless gas
| Odor = Foul, pungent, like that of rotten eggs
| Density = 1.539 g.L<sup>−1</sup> (0°C)<ref name="Pradyot Patnaik"/>
| MeltingPtC = −85.5<ref name="crc97">{{cite book | author=William M. Haynes | title=CRC Handbook of Chemistry and Physics | edition=97th | year=2016 | publisher=CRC Press | location=Boca Raton | isbn=978-1-4987-5429-3 | pages=4–87 | url=https://books.google.com/books?id=VVezDAAAQBAJ}}</ref>
| BoilingPtC = −59.55<ref name="crc97"/>
| Solubility = 3.980 g dm<sup>−3</sup> (at 20&nbsp;°C) <ref>{{cite web |title=Hydrogen sulfide |url=https://pubchem.ncbi.nlm.nih.gov/compound/Hydrogen-sulfide#section=Solubility |website=pubchem.ncbi.nlm.nih.gov |language=en}}</ref>
| VaporPressure = 1740 kPa (at 21&nbsp;°C)
| ConjugateAcid = [[Physics:Sulfonium|Sulfonium]]
| ConjugateBase = [[Chemistry:Bisulfide|Bisulfide]]
| pKa = 7.0<ref>{{cite book|last=Perrin |first=D.D. |title=Ionisation Constants of Inorganic Acids and Bases in Aqueous Solution |edition= 2nd |publisher=Pergamon Press |location=Oxford |date=1982}}</ref><ref>Bruckenstein, S.; Kolthoff, I.M., in Kolthoff, I.M.; Elving, P.J. ''Treatise on Analytical Chemistry'', Vol. 1, pt. 1; Wiley, NY, '''1959''', pp. 432–433.</ref> 
| RefractIndex = 1.000644 (0&nbsp;°C)<ref name="Pradyot Patnaik">{{cite book|first=Pradyot |last=Patnaik |title=Handbook of Inorganic Chemicals |publisher=McGraw-Hill |date=2002 |isbn=978-0-07-049439-8}}</ref>
| MagSus = &minus;25.5·10<sup>−6</sup> cm<sup>3</sup>/mol
}}
| Section3 = {{Chembox Structure
| MolShape = Bent
| Dipole = 0.97 D
| PointGroup = C<sub>2v</sub>
}}
| Section4 = {{Chembox Thermochemistry
| DeltaHf = −21&nbsp;kJ mol<sup>−1</sup><ref name=b1>{{cite book| last= Zumdahl|first= Steven S.|title =Chemical Principles |edition= 6th| publisher = Houghton Mifflin Company| year = 2009| isbn = 978-0-618-94690-7|page=A23}}</ref>
| Entropy = 206&nbsp;J mol<sup>−1</sup> K<sup>−1</sup><ref name=b1/>
| HeatCapacity = 1.003 J K<sup>−1</sup> g<sup>−1</sup>
}}
| Section7 = {{Chembox Hazards
| MainHazards = Flammable and highly toxic
| ExternalSDS = 
| GHSPictograms = {{GHS02}}{{GHS06}}{{GHS09}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|220|330|400}}
| PPhrases = {{P-phrases|210|260|271|273|284|304+340|310|320|377|381|391|403|403+233|405|501}}
| NFPA-H = 4
| NFPA-F = 4
| NFPA-R = 0
| AutoignitionPtC = 232
| FlashPtC = −82.4
| FlashPt_ref = <ref>{{cite web|url=http://www.npi.gov.au/substances/hydrogen-sulfide/index.html|title=Hydrogen sulfide|work=npi.gov.au}}</ref>
| ExploLimits = 4.3–46%
| IDLH = 100 ppm<ref name=PGCH>{{PGCH|0337}}</ref>
| REL = C 10 ppm (15&nbsp;mg/m<sup>3</sup>) [10-minute]<ref name=PGCH/> 
| PEL = C 20 ppm; 50 ppm [10-minute maximum peak]<ref name=PGCH/>
| LC50 = {{ubl|713 ppm (rat, 1 hr)|673 ppm (mouse, 1 hr)|634 ppm (mouse, 1 hr)|444 ppm (rat, 4 hr)<ref name=IDLH>{{IDLH|7783064|Hydrogen sulfide}}</ref>}}
| LCLo = {{ubl|600 ppm (human, 30 min)|800 ppm (human, 5 min)<ref name=IDLH/>}}
}}
| Section9 = {{Chembox Related
| OtherFunction_label = hydrogen chalcogenides
| OtherFunction = {{ubl|[[Chemistry:Water (molecule)|Water]]|[[Chemistry:Hydrogen selenide|Hydrogen selenide]]|[[Chemistry:Hydrogen telluride|Hydrogen telluride]]|Hydrogen polonide|[[Chemistry:Hydrogen disulfide|Hydrogen disulfide]]|[[Chemistry:Sulfanyl|Sulfanyl]]}}
| OtherCompounds = [[Chemistry:Phosphine|Phosphine]]
}}
}}
'''Hydrogen sulfide''' is a [[Chemistry:Chemical compound|chemical compound]] with the [[Chemistry:Chemical formula|formula]] '''{{chem2|H2S|auto=1}}'''. It is a colorless chalcogen-hydride [[Physics:Gas|gas]], and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs.<ref>{{Greenwood&Earnshaw2nd}}</ref>  Swedish chemist [[Biography:Carl Wilhelm Scheele|Carl Wilhelm Scheele]] is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.<ref name="americansci">{{cite journal |year = 2010|last1 = Smith|first1 = Roger P.|title = A Short History of Hydrogen Sulfide|url = https://www.americanscientist.org/article/a-short-history-of-hydrogen-sulfide|journal=American Scientist |volume=98 |issue=1 |page=6 |doi=10.1511/2010.82.6}}</ref>

Hydrogen sulfide is toxic to humans and most other animals by inhibiting [[Biology:Cellular respiration|cellular respiration]] in a manner similar to [[Chemistry:Hydrogen cyanide|hydrogen cyanide]]. When it is inhaled or its salts are ingested in high amounts,{{clarify|date=January 2022}} damage to organs occurs rapidly with symptoms ranging from breathing difficulties to convulsions and death.<ref>{{Cite journal |pmc=8614844|year=2021 |last1=Shackelford |first1=R. E. |last2=Li |first2=Y. |last3=Ghali |first3=G. E. |last4=Kevil |first4=C. G. |title=Bad Smells and Broken DNA: A Tale of Sulfur-Nucleic Acid Cooperation |journal=Antioxidants |volume=10 |issue=11 |page=1820 |doi=10.3390/antiox10111820 |pmid=34829691 |doi-access=free }}</ref><ref>{{Cite journal |doi=10.1146/annurev.pa.32.040192.000545|title=Toxicology of Hydrogen Sulfide |year=1992 |last1=Reiffenstein |first1=R. J. |last2=Hulbert |first2=W. C. |last3=Roth |first3=S. H. |journal=Annual Review of Pharmacology and Toxicology |volume=32 |pages=109–134 |pmid=1605565 }}</ref> Despite this, the [[Medicine:Human body|human body]] produces small amounts of this sulfide and its mineral salts, and uses it as a signalling molecule.<ref>{{cite journal|pmc=4369258|year=2015|last1=Bos|first1=E. M|title=Hydrogen sulfide: Physiological properties and therapeutic potential in ischaemia|journal=British Journal of Pharmacology|volume=172|issue=6|pages=1479–1493|last2=Van Goor|first2=H|last3=Joles|first3=J. A|last4=Whiteman|first4=M|last5=Leuvenink|first5=H. G|doi=10.1111/bph.12869|doi-access=free|pmid=25091411}}</ref>

Hydrogen sulfide is often produced from the microbial breakdown of [[Chemistry:Organic matter|organic matter]] in the absence of oxygen, such as in swamps and sewers; this process is commonly known as [[Physics:Anaerobic digestion|anaerobic digestion]], which is done by [[Earth:Sulfate-reducing microorganisms|sulfate-reducing microorganisms]]. It also occurs in [[Physics:Volcanic gas|volcanic gas]]es, [[Chemistry:Natural gas|natural gas]] deposits, and sometimes in well-drawn water.

==Properties==
Hydrogen sulfide is slightly denser than air. A mixture of {{chem2|H2S}} and air can be explosive. In general, hydrogen sulfide acts as a [[Chemistry:Reducing agent|reducing agent]], although in the presence of a base, it can act as an acid by donating a proton and forming {{chem2|SH−}}.

Hydrogen sulfide burns in oxygen with a blue flame to form [[Chemistry:Sulfur dioxide|sulfur dioxide]] ({{chem2|SO2}}) and [[Chemistry:Water (molecule)|water]]:

:{{chem2|2 H2S + 3 O2 → 2 SO2 + 2 H2O}}

If an excess of oxygen is present, [[Chemistry:Sulfur trioxide|sulfur trioxide]] ({{chem2|SO3}}) is formed, which quickly hydrates to [[Chemistry:Sulfuric acid|sulfuric acid]]:

:{{chem2|H2S + 2 O2 → H2SO4}}

At high temperatures or in the presence of [[Chemistry:Catalyst|catalyst]]s, sulfur dioxide reacts with hydrogen sulfide to form elemental [[Chemistry:Sulfur|sulfur]] and [[Chemistry:Water|water]]. This reaction is exploited in the [[Chemistry:Claus process|Claus process]], an important industrial method to dispose of hydrogen sulfide.

Hydrogen sulfide is slightly soluble in water and acts as a [[Chemistry:Weak acid|weak acid]] ([[Chemistry:Acid dissociation constant|p''K''<sub>a</sub>]]&nbsp;=&nbsp;6.9 in 0.01–0.1&nbsp;mol/litre solutions at 18&nbsp;°C), giving the hydrosulfide ion {{chem2|HS-}} (also written {{chem2|SH-}}). Hydrogen sulfide and its solutions are colorless. When exposed to air, it slowly oxidizes to form elemental sulfur, which is not soluble in water. The [[Chemistry:Sulfide|sulfide]] anion {{chem2|S(2-)}} is not formed in aqueous solution.<ref>{{cite journal|last1=May|first1=P.M.|last2=Batka|first2=D.|last3=Hefter|first3=G.|last4=Könignberger|first4=E.|last5=Rowland|first5=D.|title=Goodbye to S2-|journal=Chem. Comm.|volume=54|issue=16|pages=1980–1983|date=2018|doi=10.1039/c8cc00187a|pmid=29404555}}</ref>

Hydrogen sulfide reacts with metal ions to form metal sulfides, which are insoluble, often dark colored solids. [[Chemistry:Lead(II) acetate|Lead(II) acetate]] paper is used to detect hydrogen sulfide because it readily converts to [[Chemistry:Lead(II) sulfide|lead(II) sulfide]], which is black. Treating metal sulfides with strong acid or electrolysis often liberates hydrogen sulfide. Hydrogen sulfide is also responsible for [[Chemistry:Tarnish|tarnish]]ing on various metals including [[Chemistry:Copper|copper]] and [[Chemistry:Silver|silver]]; the chemical responsible for black toning found on silver coins is [[Chemistry:Silver sulfide|silver sulfide]] ({{chem2|Ag2S}}), which is produced when the silver on the surface of the coin reacts with atmospheric hydrogen sulfide.<ref>{{Cite journal |last=JCE staff|date=March 2000 |title=Silver to Black - and Back|url=https://pubs.acs.org/doi/pdf/10.1021/ed077p328A|journal=Journal of Chemical Education|volume=77|issue=3|pages=328A|doi=10.1021/ed077p328a |bibcode=2000JChEd..77R.328J |issn=0021-9584}}</ref>

At pressures above 90&nbsp;GPa (gigapascal), hydrogen sulfide becomes a metallic conductor of electricity. When cooled below a [[Physics:Superconductivity#Superconducting phase transition|critical temperature]] this high-pressure phase exhibits [[Physics:Superconductivity|superconductivity]]. The critical temperature increases with pressure, ranging from 23&nbsp;K at 100&nbsp;GPa to 150&nbsp;K at 200&nbsp;GPa.<ref name=Drozdov2014>{{Cite arXiv|last1= Drozdov|first1=A.|last2=Eremets|first2=M. I.|last3=Troyan|first3=I. A.|title=Conventional superconductivity at 190 K at high pressures|eprint=1412.0460|year=2014|class=cond-mat.supr-con}}</ref> If hydrogen sulfide is pressurized at higher temperatures, then cooled, the critical temperature reaches {{convert|203|K|°C}}, the highest accepted superconducting critical temperature as of 2015. By substituting a small part of sulfur with phosphorus and using even higher pressures, it has been predicted that it may be possible to raise the critical temperature to above {{convert|0|°C|K}} and achieve [[Physics:Room-temperature superconductor|room-temperature superconductivity]].<ref name=cart15>{{cite journal |last1=Cartlidge |first1=Edwin |title=Superconductivity record sparks wave of follow-up physics |journal=Nature |date=August 2015 |volume=524 |issue=7565 |pages=277 |doi=10.1038/nature.2015.18191 |pmid=26289188 |bibcode=2015Natur.524..277C |doi-access=free }}</ref>

Hydrogen sulfide decomposes without a presence of a catalyst under atmospheric pressure around 1200&nbsp;°C into hydrogen and sulfur.<ref>{{cite journal |title=The direct conversion of hydrogen sulfide to hydrogen and sulfur |journal=International Journal of Hydrogen Energy |date=1998 |volume=23 |issue=6 |pages=451–456 |doi=10.1016/S0360-3199(97)00099-2|last1=Faraji |first1=F. }}</ref>

The gas has a characteristic egg-like odour.

==Production==
Hydrogen sulfide is most commonly obtained by its separation from [[Chemistry:Sour gas|sour gas]], which is natural gas with a high content of {{chem2|H2S}}. It can also be produced by treating [[Chemistry:Hydrogen|hydrogen]] with molten elemental sulfur at about 450&nbsp;°C. Hydrocarbons can serve as a source of hydrogen in this process.<ref name=ullmann>{{cite book |doi=10.1002/14356007.a13_467 |chapter=Hydrogen Sulfide |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Pouliquen |first1=Francois |last2=Blanc |first2=Claude |last3=Arretz |first3=Emmanuel |last4=Labat |first4=Ives |last5=Tournier-Lasserve |first5=Jacques |last6=Ladousse |first6=Alain |last7=Nougayrede |first7=Jean |last8=Savin |first8=Gérard |last9=Ivaldi |first9=Raoul |last10=Nicolas |first10=Monique |last11=Fialaire |first11=Jean |last12=Millischer |first12=René |last13=Azema |first13=Charles |last14=Espagno |first14=Lucien |last15=Hemmer |first15=Henri |last16=Perrot |first16=Jacques |isbn=3527306730 }}</ref>
:{{chem2|S + H2  ->  H2S}}
The very favorable thermodynamics for the hydrogenation of sulfur implies that the dehydrogenation (or [[Chemistry:Cracking|cracking]] of hydrogen sulfide would require very high temperatures.<ref>{{cite journal |doi=10.1016/j.cej.2023.141398 |title=Hydrogen sulfide (H2S) conversion to hydrogen (H2) and value-added chemicals: Progress, challenges and outlook |date=2023 |last1=Chan |first1=Yi Herng |last2=Loy |first2=Adrian Chun Minh |last3=Cheah |first3=Kin Wai |last4=Chai |first4=Slyvester Yew Wang |last5=Ngu |first5=Lock Hei |last6=How |first6=Bing Shen |last7=Li |first7=Claudia |last8=Lock |first8=Serene Sow Mun |last9=Wong |first9=Mee Kee |last10=Yiin |first10=Chung Loong |last11=Chin |first11=Bridgid Lai Fui |last12=Chan |first12=Zhe Phak |last13=Lam |first13=Su Shiung |journal=Chemical Engineering Journal |volume=458 |s2cid=255887336 |url=http://ir.unimas.my/id/eprint/41182/3/Hydrogen%20sulfide%20%28.pdf }}</ref>

Sulfate-reducing (resp. [[Biology:Sulfur-reducing bacteria|sulfur-reducing]]) bacteria generate usable energy under low-oxygen conditions by using sulfates (resp. elemental sulfur) to [[Chemistry:Redox|oxidize]] organic compounds or hydrogen; this produces hydrogen sulfide as a waste product.

A standard lab preparation is to treat [[Chemistry:Iron(II) sulfide|ferrous sulfide]] with a strong acid in a Kipp generator:
:{{chem2|FeS + 2 HCl → FeCl2 + H2S}}
For use in [[Chemistry:Qualitative inorganic analysis|qualitative inorganic analysis]], [[Chemistry:Thioacetamide|thioacetamide]] is used to generate {{chem2|H2S}}:
:{{chem2|CH3C(S)NH2 + H2O → CH3C(O)NH2 + H2S}}

Many metal and nonmetal sulfides, e.g. [[Chemistry:Aluminium sulfide|aluminium sulfide]], [[Chemistry:Phosphorus pentasulfide|phosphorus pentasulfide]], [[Chemistry:Silicon disulfide|silicon disulfide]] liberate hydrogen sulfide upon exposure to water:<ref>{{cite book|last=McPherson|first=William|title=Laboratory manual|year=1913|publisher=Ginn and Company|location=Boston|page=445|url=https://books.google.com/books?id=oaMe7OtctlIC&q=%22aluminium+sulfide%22}}</ref>
:{{chem2|6 H2O + Al2S3 → 3 H2S + 2 Al(OH)3}}

This gas is also produced by heating sulfur with solid organic compounds and by reducing sulfurated organic compounds with hydrogen.

Water heaters can aid the conversion of [[Chemistry:Sulfate|sulfate]] in water to hydrogen sulfide gas. This is due to providing a warm environment sustainable for sulfur bacteria and maintaining the reaction which interacts between sulfate in the water and the water heater anode, which is usually made from [[Chemistry:Magnesium|magnesium]] metal.<ref>{{cite web|title=Why Does My Water Smell Like Rotten Eggs? Hydrogen Sulfide and Sulfur Bacteria in Well Water|url=http://www.health.state.mn.us/divs/eh/wells/waterquality/hydrosulfide.html|website=Minnesota Department of Health|access-date=1 December 2014|archive-date=11 March 2015|archive-url=https://web.archive.org/web/20150311185440/http://www.health.state.mn.us/divs/eh/wells/waterquality/hydrosulfide.html|url-status=dead}}</ref>

=== Biosynthesis in the body ===
Hydrogen sulfide can be generated in cells via enzymatic or non-enzymatic pathways. Three enzymes catalyze formation of {{chem|H|2|S}}: [[Biology:Cystathionine gamma-lyase|cystathionine γ-lyase]] (CSE), [[Biology:Cystathionine beta synthase|cystathionine β-synthetase]] (CBS), and [[Biology:3-mercaptopyruvate sulfurtransferase|3-mercaptopyruvate sulfurtransferase]] (3-MST).<ref name="Huang-2015">{{Citation|last1=Huang|first1=Caleb Weihao|title=H2S Synthesizing Enzymes: Biochemistry and Molecular Aspects|volume=230|date=2015|work=Chemistry, Biochemistry and Pharmacology of Hydrogen Sulfide|pages=3–25|publisher=Springer International Publishing|doi=10.1007/978-3-319-18144-8_1|pmid=26162827|isbn=9783319181431|last2=Moore|first2=Philip Keith|series=Handbook of Experimental Pharmacology }}</ref> CBS and CSE are the main proponents of {{chem2|H2S}} biogenesis, which follows the trans-sulfuration pathway.<ref name="Kabil-2011">{{cite journal |last1=Kabil |first1=Omer |last2=Vitvitsky |first2=Victor |last3=Xie |first3=Peter |last4=Banerjee |first4=Ruma |title=The Quantitative Significance of the Transsulfuration Enzymes for H 2 S Production in Murine Tissues |journal=Antioxidants & Redox Signaling |date=15 July 2011 |volume=15 |issue=2 |pages=363–372 |doi=10.1089/ars.2010.3781 |pmid=21254839 |pmc=3118817 }}</ref> These enzymes have been identified in a breadth of biological cells and tissues, and their activity is induced by a number of disease states.<ref name="Kabil-2014">{{cite journal |last1=Kabil |first1=Omer |last2=Banerjee |first2=Ruma |title=Enzymology of H<sub>2</sub>S Biogenesis, Decay and Signaling |journal=Antioxidants & Redox Signaling |date=10 February 2014 |volume=20 |issue=5 |pages=770–782 |doi=10.1089/ars.2013.5339 |pmid=23600844 |pmc=3910450 }}</ref> These enzymes are characterized by the transfer of a sulfur atom from methionine to serine to form a cysteine molecule.<ref name="Kabil-2011" /> 3-MST also contributes to hydrogen sulfide production by way of the cysteine catabolic pathway.<ref name="Kabil-2014"/><ref name="Kabil-2011" /> Dietary amino acids, such as methionine and cysteine serve as the primary substrates for the transulfuration pathways and in the production of hydrogen sulfide. Hydrogen sulfide can also be derived from proteins such as [[Biology:Ferredoxin|ferredoxin]]s and [[Biology:Rieske protein|Rieske protein]]s.<ref name="Kabil-2014"/>

===Signalling role===
{{chem2|H2S}} in the body acts as a gaseous signaling molecule with implications for health and in diseases.<ref name="Huang-2015"/> <ref>{{cite journal |last1=Wallace |first1=John L. |last2=Wang |first2=Rui |title=Hydrogen sulfide-based therapeutics: exploiting a unique but ubiquitous gasotransmitter |journal=Nature Reviews Drug Discovery |date=May 2015 |volume=14 |issue=5 |pages=329–345 |doi=10.1038/nrd4433 |pmid=25849904 |s2cid=5361233 }}</ref><ref name="powell">{{cite journal | last1=Powell | first1=Chadwick R. | last2=Dillon | first2=Kearsley M. | last3=Matson | first3=John B. | title=A review of hydrogen sulfide (H2S) donors: Chemistry and potential therapeutic applications | journal=Biochemical Pharmacology | volume=149 | year=2018 | issn=0006-2952 | pmid=29175421 | pmc=5866188 | doi=10.1016/j.bcp.2017.11.014 | pages=110–123}}</ref> 

Hydrogen sulfide is involved in [[Medicine:Vasodilation|vasodilation]] in animals, as well as in increasing seed germination and stress responses in plants.<ref name="Hancock-2017"/> Hydrogen sulfide signaling is moderated by [[Biology:Reactive oxygen species|reactive oxygen species]] (ROS) and [[Chemistry:Reactive nitrogen species|reactive nitrogen species]] (RNS).<ref name="Hancock-2017" /> {{chem2|H2S}} has been shown to interact with NO resulting in several different cellular effects, as well as the formation of another signal called nitrosothiol.<ref name="Hancock-2017" /> Hydrogen sulfide is also known to increase the levels of glutathione, which acts to reduce or disrupt ROS levels in cells.<ref name="Hancock-2017" /> 

The field of {{chem2|H2S}} biology has advanced from environmental toxicology to investigate the roles of endogenously produced {{chem2|H2S}} in physiological conditions and in various pathophysiological states.<ref>{{cite journal |last1=Szabo |first1=Csaba |title=A Timeline of Hydrogen sulfide (H<sub>2</sub>S) Research: From Environmental toxin to biological mediator |journal=Biochemical Pharmacology |date=March 2018 |volume=149 |pages=5–19 |doi=10.1016/j.bcp.2017.09.010 |pmid=28947277 |pmc=5862769 }}</ref>  {{chem2|H2S}} has been implicated in cancer and Down syndrome and vascular disease.<ref>{{cite journal |last1=Szabo |first1=Csaba |last2=Papapetropoulos |first2=Andreas |title=International Union of Basic and Clinical Pharmacology. CII: Pharmacological Modulation of H<sub>2</sub>S Levels: H<sub>2</sub>S Donors and H<sub>2</sub>S Biosynthesis Inhibitors |journal=Pharmacological Reviews |date=October 2017 |volume=69 |issue=4 |pages=497–564 |doi=10.1124/pr.117.014050 |pmid=28978633 |pmc=5629631 }}</ref><ref>{{cite journal |last1=Wang |first1=Rui |title=Physiological Implications of Hydrogen Sulfide: A Whiff Exploration That Blossomed |journal=Physiological Reviews |date=April 2012 |volume=92 |issue=2 |pages=791–896 |doi=10.1152/physrev.00017.2011 |pmid=22535897 |s2cid=21932297 }}</ref><ref>{{cite journal |last1=Li |first1=Zhen |last2=Polhemus |first2=David J. |last3=Lefer |first3=David J. |title=Evolution of Hydrogen Sulfide Therapeutics to Treat Cardiovascular Disease |journal=Circulation Research |date=17 August 2018 |volume=123 |issue=5 |pages=590–600 |doi=10.1161/CIRCRESAHA.118.311134 |pmid=30355137 |s2cid=53027283 |doi-access=free }}</ref><ref>{{cite journal |last1=Kimura |first1=Hideo |title=Signalling by Hydrogen Sulfide and Polysulfides via Protein S-Sulfuration |journal=British Journal of Pharmacology |date=February 2020 |volume=177 |issue=4 |pages=720–733 |doi=10.1111/bph.14579 |pmid=30657595 |pmc=7024735 }}</ref>

It inhibits Complex IV of the mitochondrial electron transport chain, which effectively reduces ATP generation and biochemical activity within cells.<ref name="Hancock-2017">{{Cite book|title=Cell signalling|last=Hancock|first=John T.|isbn=9780199658480|edition= Fourth|location=Oxford, United Kingdom |oclc=947925636|year=2017}}</ref>

==Uses==
===Production of sulfur, thioorganic compounds, and alkali metal sulfides===
The main use of hydrogen sulfide is as a precursor to elemental sulfur. Several organosulfur compounds are produced using hydrogen sulfide. These include [[Chemistry:Methanethiol|methanethiol]], [[Chemistry:Ethanethiol|ethanethiol]], and [[Chemistry:Thioglycolic acid|thioglycolic acid]].<ref name=ullmann/>

Upon combining with [[Chemistry:Alkali metal|alkali metal]] bases, hydrogen sulfide converts to alkali hydrosulfides such as [[Chemistry:Sodium hydrosulfide|sodium hydrosulfide]] and [[Chemistry:Sodium sulfide|sodium sulfide]]:
:{{chem2|H2S + NaOH → NaSH + H2O}}
:{{chem2|NaSH + NaOH → Na2S + H2O}}

These compounds are used in the paper making industry. Specifically, salts of {{chem2|SH−}} break bonds between lignin and cellulose components of [[Chemistry:Pulp (paper)|pulp]] in the [[Chemistry:Kraft process|Kraft process]].<ref name=ullmann/>

Reversibly sodium sulfide in the presence of acids turns into hydrosulfides and hydrogen sulfide; this supplies hydrosulfides in organic solutions and is utilized in the production of [[Chemistry:Thiophenol|thiophenol]].<ref>{{cite journal |last1=Khazaei |first1=Ardeshir |last2=Kazem-Rostami |first2=Masoud |last3=Moosavi-Zare |first3=Ahmad |last4=Bayat |first4=Mohammad |last5=Saednia |first5=Shahnaz |title=Novel One-Pot Synthesis of Thiophenols from Related Triazenes under Mild Conditions |journal=Synlett |date=August 2012 |volume=23 |issue=13 |pages=1893–1896 |doi=10.1055/s-0032-1316557 |s2cid=196805424 }}</ref>

===Precursor to metal sulfides===
As indicated above, many metal ions react with hydrogen sulfide to give the corresponding metal sulfides.  Oxidic ores are sometimes treated with hydrogen sulfide to give the corresponding metal sulfides which are more readily purified byy flotation.<ref name=ullmann/> Metal parts are sometimes [[Engineering:Passivation|passivated]] with hydrogen sulfide. Catalysts used in [[Chemistry:Hydrodesulfurization|hydrodesulfurization]] are routinely activated with hydrogen sulfide.

Hydrogen sulfide was a reagentin the [[Chemistry:Qualitative inorganic analysis|qualitative inorganic analysis]] of metal ions. In these analyses, heavy metal (and [[Chemistry:Nonmetal|nonmetal]]) ions (e.g., Pb(II), Cu(II), Hg(II), As(III)) are precipitated from solution upon exposure to {{chem2|H2S}}. The components of the resulting solid are then identified by their reactivity.

===Miscellaneous applications===
Hydrogen sulfide is used to separate deuterium oxide, or [[Chemistry:Heavy water|heavy water]], from normal water via the [[Physics:Girdler sulfide process|Girdler sulfide process]].

Scientists from the [[Organization:University of Exeter|University of Exeter]] discovered that cell exposure to small amounts of hydrogen sulfide gas can prevent [[Biology:Mitochondria|mitochondria]]l damage. When the cell is stressed with disease, enzymes are drawn into the cell to produce small amounts of hydrogen sulfide. This study could have further implications on preventing [[Medicine:Stroke|stroke]]s, heart disease and [[Medicine:Arthritis|arthritis]].<ref>{{cite magazine|last1=Stampler|first1=Laura|title=A Stinky Compound May Protect Against Cell Damage, Study Finds|url=http://time.com/2976464/rotten-eggs-hydrogen-sulfide-mitochondria/|magazine=Time|access-date=1 December 2014}}</ref>

Depending on the level of toning present, coins that have been subject to toning by hydrogen sulfide and other sulfur-containing compounds may add to the numismatic value of a coin based on the toning's aesthetics. Coins can also be intentionally treated with hydrogen sulfide to induce toning, though artificial toning can be distinguished from natural toning, and is generally criticised among collectors.<ref>{{Cite web|title=Coin Toning 101: The Differences between Naturally and Artificially Toned Coins|url=https://www.originalskincoins.com/blogs/news/coin-toning-101-the-differences-between-naturally-and-artificially-toned-coins|access-date=2021-10-15 |website=Original Skin Coins}}</ref>

A suspended animation-like state has been induced in rodents with the use of hydrogen sulfide, resulting in [[Physics:Hypothermia|hypothermia]] with a concomitant reduction in metabolic rate. Oxygen demand was also reduced, thereby protecting against [[Medicine:Hypoxia (medical)|hypoxia]]. In addition, hydrogen sulfide has been shown to reduce inflammation in various situations.<ref>{{cite journal |last1=Aslami |first1=H |last2=Schultz |first2=MJ |last3=Juffermans |first3=NP |title=Potential applications of hydrogen sulfide-induced suspended animation. |journal=Current Medicinal Chemistry |date=2009 |volume=16 |issue=10 |pages=1295–303 |pmid=19355886 |doi=10.2174/092986709787846631 }}</ref>

=== Occurrence ===
[[Image:Deposit from hydrogen sulphide.jpg|thumb|Deposit of sulfur on a rock, caused by volcanic gas]]

[[Earth:Volcano|Volcano]]es and some [[Earth:Hot spring|hot spring]]s (as well as [[Earth:Mineral spring|cold springs]]) emit some {{chem2|H2S}}. Hydrogen sulfide can be present naturally in well water, often as a result of the action of sulfate-reducing bacteria.<ref>{{cite web|title=Hydrogen Sulphide In Well Water|url=https://extension.psu.edu/hydrogen-sulfide-rotten-egg-odor-in-water-wells|access-date=4 September 2018}}</ref>{{better source needed|date = January 2020}} Hydrogen sulfide is produced by the human body in small quantities through bacterial breakdown of proteins containing sulfur in the intestinal tract, therefore it contributes to the characteristic odor of flatulence. It is also produced in the mouth (halitosis).<ref name="ATSDR">{{cite web|author=Agency for Toxic Substances and Disease Registry|date=July 2006|title=Toxicological Profile For Hydrogen Sulfide|url=http://www.atsdr.cdc.gov/toxprofiles/tp114.pdf|access-date=2012-06-20|page=154}}</ref>

A portion of global {{chem2|H2S}} emissions are due to human activity. By far the largest industrial source of {{chem2|H2S}} is [[Chemistry:Oil refinery|petroleum refineries]]: The [[Chemistry:Hydrodesulfurization|hydrodesulfurization]] process liberates sulfur from [[Chemistry:Petroleum|petroleum]] by the action of hydrogen. The resulting {{chem2|H2S}} is converted to elemental sulfur by partial combustion via the [[Chemistry:Claus process|Claus process]], which is a major source of elemental sulfur. Other anthropogenic sources of hydrogen sulfide include [[Chemistry:Coke (fuel)|coke]] ovens, [[Engineering:Paper mill|paper mill]]s (using the Kraft process), tanneries and [[Engineering:Sewerage|sewerage]]. {{chem2|H2S}} arises from virtually anywhere where elemental sulfur comes in contact with organic material, especially at high temperatures. Depending on environmental conditions, it is responsible for deterioration of material through the action of some sulfur oxidizing microorganisms. It is called [[Biology:Biogenic sulfide corrosion|biogenic sulfide corrosion]].

In 2011 it was reported that increased concentrations of {{chem2|H2S}} were observed in the [[Earth:Bakken formation|Bakken formation]] crude, possibly due to oil field practices, and presented challenges such as "health and environmental risks, corrosion of wellbore, added expense with regard to materials handling and pipeline equipment, and additional refinement requirements".<ref>{{cite web|url=http://www.onepetro.org/mslib/servlet/onepetropreview?id=SPE-141434-MS|title=Home - OnePetro|author=OnePetro|work=onepetro.org|access-date=2013-08-14|archive-date=2013-10-14|archive-url=https://web.archive.org/web/20131014053027/http://www.onepetro.org/mslib/servlet/onepetropreview?id=SPE-141434-MS|url-status=dead}}</ref>

Besides living near gas and oil drilling operations, ordinary citizens can be exposed to hydrogen sulfide by being near [[Earth:Sewage treatment|waste water treatment]] facilities, landfills and farms with manure storage. Exposure occurs through breathing contaminated air or drinking contaminated water.<ref>{{cite web|title=Hydrogen Sulfide|url=https://www.atsdr.cdc.gov/toxfaqs/tfacts114.pdf|publisher=Agency for Toxic Substances and Disease Registry|date=December 2016}}</ref>

In municipal waste landfill sites, the burial of [[Chemistry:Organic matter|organic material]] rapidly leads to the production of [[Physics:Anaerobic digestion|anaerobic digestion]] within the waste mass and, with the humid atmosphere and relatively high temperature that accompanies biodegradation, [[Physics:Biogas|biogas]] is produced as soon as the air within the waste mass has been reduced. If there is a source of sulfate bearing material, such as plasterboard or natural [[Chemistry:Gypsum|gypsum]] (calcium sulfate dihydrate), under anaerobic conditions [[Earth:Sulfate-reducing microorganisms|sulfate reducing bacteria]] converts this to hydrogen sulfide. These bacteria cannot survive in air but the moist, warm, anaerobic conditions of buried waste that contains a high source of carbon &ndash; in inert landfills, paper and glue used in the fabrication of products such as [[Chemistry:Drywall|plasterboard]] can provide a rich source of carbon<ref>{{Cite journal |doi = 10.1016/S1093-0191(00)00056-3|title = Sulfate leaching from recovered construction and demolition debris fines|journal = Advances in Environmental Research|volume = 5|issue = 3|pages = 203–217|year = 2001|last1 = Jang|first1 = Yong-Chul|last2 = Townsend|first2 = Timothy}}</ref> &ndash; is an excellent environment for the formation of hydrogen sulfide.

In industrial anaerobic digestion processes, such as [[Earth:Wastewater treatment|waste water treatment]] or the [[Physics:Anaerobic digestion|digestion of organic waste from agriculture]], hydrogen sulfide can be formed from the reduction of sulfate and the degradation of amino acids and proteins within organic compounds.<ref>{{Cite web|url=http://www.valorgas.soton.ac.uk/Pub_docs/JyU%20SS%202011/CC%201.pdf|title=Anaerobic digestion fundamentals|last=Cavinato|first=C. |date=2013|orig-year=2013}}</ref> Sulfates are relatively non-inhibitory to [[Biology:Methanobacteria|methane forming bacteria]] but can be reduced to {{chem2|H2S}} by [[Earth:Sulfate-reducing microorganisms|sulfate reducing bacteria]], of which there are several genera.<ref>{{cite journal |last1=Pokorna |first1=Dana |last2=Zabranska |first2=Jana |title=Sulfur-oxidizing bacteria in environmental technology |journal=Biotechnology Advances |date=November 2015 |volume=33 |issue=6 |pages=1246–1259 |doi=10.1016/j.biotechadv.2015.02.007 |pmid=25701621 }}</ref>

===Removal from water===

A number of processes have been designed to remove hydrogen sulfide from drinking water.<ref>{{cite web |last1=Lemley |first1=Ann T. |last2=Schwartz |first2=John J. |last3=Wagenet |first3=Linda P. |title=Hydrogen Sulfide in Household Drinking Water |url=http://waterquality.cce.cornell.edu/publications/CCEWQ-07-HydrogenSulfide.pdf |publisher=Cornell University |archive-url=https://web.archive.org/web/20190819132148/http://waterquality.cce.cornell.edu/publications/CCEWQ-07-HydrogenSulfide.pdf |archive-date=19 August 2019 |url-status=dead}}</ref>

;Continuous chlorination: For levels up to 75&nbsp;mg/L [[Chemistry:Chlorine|chlorine]] is used in the purification process as an oxidizing chemical to react with hydrogen sulfide. This reaction yields insoluble solid sulfur. Usually the chlorine used is in the form of [[Chemistry:Sodium hypochlorite|sodium hypochlorite]].<ref>{{cite web|title=Hydrogen Sulfide (Rotten Egg Odor) in Pennsylvania Groundwater Wells|url=http://extension.psu.edu/natural-resources/water/drinking-water/water-testing/pollutants/hydrogen-sulfide-rotten-egg-odor-in-pennsylvania-groundwater-wells|website=Penn State|publisher=Penn State College of Agricultural Sciences|access-date=1 December 2014|archive-date=4 January 2015|archive-url=https://web.archive.org/web/20150104222350/http://extension.psu.edu/natural-resources/water/drinking-water/water-testing/pollutants/hydrogen-sulfide-rotten-egg-odor-in-pennsylvania-groundwater-wells|url-status=dead}}</ref>

;Aeration: For concentrations of hydrogen sulfide less than 2&nbsp;mg/L [[Physics:Aeration|aeration]] is an ideal treatment process. Oxygen is added to water and a reaction between oxygen and hydrogen sulfide react to produce odorless sulfate.<ref>{{cite web|last1=McFarland|first1=Mark L.|last2=Provin|first2=T. L.|title=Hydrogen Sulfide in Drinking Water Treatment Causes and Alternatives|url=http://soiltesting.tamu.edu/publications/L-5312.pdf|publisher=Texas A&M University|access-date=1 December 2014}}</ref>

;Nitrate addition: [[Chemistry:Calcium nitrate|Calcium nitrate]] can be used to prevent hydrogen sulfide formation in wastewater streams.

===Removal from fuel gases===
Hydrogen sulfide is commonly found in raw natural gas and biogas. It is typically removed by [[Physics:Amine gas treating|amine gas treating]] technologies. In such processes, the hydrogen sulfide is first converted to an ammonium salt, whereas the natural gas is unaffected.
:{{chem2|RNH2 + H2S ⇌ [RNH3]+ + SH−}}
The bisulfide anion is subsequently regenerated by heating of the amine sulfide solution. Hydrogen sulfide generated in this process is typically converted to elemental sulfur using the Claus Process.

[[Image:AmineTreating.png|frame|center|[[Process flow diagram|Process flow diagram]] of a typical amine treating process used in petroleum refineries, natural gas processing plants and other industrial facilities]]

==Safety==
The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is ''stinkdamp''. Hydrogen sulfide is a highly toxic and flammable gas ([[Astronomy:Flammability limit|flammable range]]: 4.3–46%). It can poison several systems in the body, although the [[Biology:Nervous system|nervous system]] is most affected.{{cn|date=December 2023}} The toxicity of {{chem2|H2S}} is comparable with that of [[Chemistry:Carbon monoxide|carbon monoxide]].<ref name="pmid23111938">{{cite journal |last1=Lindenmann |first1=J. |last2=Matzi |first2=V. |last3=Neuboeck |first3=N. |last4=Ratzenhofer-Komenda |first4=B. |last5=Maier |first5=A |last6=Smolle-Juettner |first6=F. M. |title=Severe hydrogen sulphide poisoning treated with 4-dimethylaminophenol and hyperbaric oxygen |journal=Diving and Hyperbaric Medicine |volume=40 |issue=4 |pages=213–217 |date=December 2010 |pmid=23111938 |url=http://archive.rubicon-foundation.org/10235 |archive-url=https://archive.today/20130615171751/http://archive.rubicon-foundation.org/10235 |url-status=usurped |archive-date=June 15, 2013 |access-date=2013-06-07}}</ref> It binds with [[Chemistry:Iron|iron]] in the [[Biology:Mitochondria|mitochondria]]l [[Biology:Cytochrome|cytochrome]] [[Biology:Enzyme|enzyme]]s, thus preventing [[Biology:Cellular respiration|cellular respiration]]. Its toxic properties were described in detail in 1843 by Justus von Liebig.<ref>{{Cite journal|last=Harrison|first=J. Bower|date=1843-11-18|title=Some Remarks on the Production of Sulphuretted Hydrogen Gas in the Alimentary Canal, and Its Effects on the System |journal=Provincial Medical Journal and Retrospect of the Medical Sciences, BMJ|volume=7|issue=164 |pages=127–129|jstor=25492480}}</ref>

Even before hydrogen sulfide was discovered, Italian physician Bernardino Ramazzini hypothesized in his 1713 book De Morbis Artificum Diatriba that occupational diseases of sewer-workers and blackening of coins in their clothes may be caused by an unknown invisible volatile acid (moreover, in late 18th century toxic gas emanation from [[Engineering:Paris sewers|Paris sewers]] became a problem for the citizens and authorities).<ref>{{Cite web |date=2017-02-06 |title=A Short History of Hydrogen Sulfide |url=https://www.americanscientist.org/article/a-short-history-of-hydrogen-sulfide |access-date=2023-12-25 |website=American Scientist |language=en}}</ref>

Although very pungent at first (it smells like rotten eggs<ref>{{cite web|title=Why Does My Water Smell Like Rotten Eggs? |url=https://www.health.state.mn.us/communities/environment/water/wells/waterquality/hydrosulfide.html |publisher=Minnesota Department of Health |access-date=20 January 2020}}</ref>), it quickly deadens the sense of smell, creating temporary [[Medicine:Anosmia|anosmia]],<ref>{{Cite book|last=Contaminants|first=National Research Council (US) Committee on Emergency and Continuous Exposure Guidance Levels for Selected Submarine |url=https://www.ncbi.nlm.nih.gov/books/NBK219913/|title=Hydrogen Sulfide|date=2009|publisher=National Academies Press (US)|language=en}}</ref> so victims may be unaware of its presence until it is too late. Safe handling procedures are provided by its safety data sheet (SDS).<ref>{{cite web 
 |last=[[Organization:Iowa State University|Iowa State University]] 
 |publisher=Department of Chemistry
 |title=Hydrogen Sulfide Material Safety Data Sheet 
 |url=http://avogadro.chem.iastate.edu/MSDS/hydrogen_sulfide.pdf 
 |access-date=2009-03-14 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20090327094137/http://avogadro.chem.iastate.edu/MSDS/hydrogen_sulfide.pdf 
 |archive-date=2009-03-27 
 }}</ref>

===Low-level exposure===
Since hydrogen sulfide occurs naturally in the body, the environment, and the gut, enzymes exist to metabolize it. At some threshold level, believed to average around 300–350 ppm, the oxidative enzymes become overwhelmed. Many personal safety gas detectors, such as those used by utility, sewage and petrochemical workers, are set to alarm at as low as 5 to 10 ppm and to go into high alarm at 15 ppm.  Metabolism causes oxidation to sulfate, which is harmless.<ref>{{cite journal |last1=Ramasamy |first1=S. |last2=Singh |first2=S. |last3=Taniere |first3=P. |last4=Langman |first4=M. J. S. |last5=Eggo |first5=M. C. |title=Sulfide-detoxifying enzymes in the human colon are decreased in cancer and upregulated in differentiation |journal=American Journal of Physiology. Gastrointestinal and Liver Physiology |date=August 2006 |volume=291 |issue=2 |pages=G288–G296 |doi=10.1152/ajpgi.00324.2005 |pmid=16500920 |s2cid=15443357 }}</ref> Hence, low levels of hydrogen sulfide may be tolerated indefinitely.

Exposure to lower concentrations can result in [[Biology:Human eye|eye]] irritation, a sore throat and cough, nausea, shortness of breath, and fluid in the [[Medicine:Lung|lung]]s ([[Medicine:Pulmonary edema|pulmonary edema]]).<ref name="pmid23111938"/> These effects are believed to be due to hydrogen sulfide combining with [[Chemistry:Alkali|alkali]] present in moist surface tissues to form [[Chemistry:Sodium sulfide|sodium sulfide]], a caustic.<ref>{{cite book |last=Lewis |first=R.J. |title=Sax's Dangerous Properties of Industrial Materials |edition=9th |location=New York, NY |publisher=Van Nostrand Reinhold |date=1996 }}{{page needed|date=May 2022}}</ref> These symptoms usually subside in a few weeks.

Long-term, low-level exposure may result in fatigue, loss of appetite, [[Medicine:Headache|headache]]s, irritability, poor memory, and [[Medicine:Dizziness|dizziness]]. Chronic exposure to low level {{chem2|H2S}} (around 2 [[Parts per million|ppm]]) has been implicated in increased miscarriage and reproductive health issues among Russian and Finnish wood pulp workers,<ref>{{cite journal|last1=Hemminki |first1=K. |last2=Niemi |first2=M. L. |date=1982 |journal=Int. Arch. Occup. Environ. Health |volume=51 |issue=1 |pages=55–63|title=Community study of spontaneous abortions: relation to occupation and air pollution by sulfur dioxide, hydrogen sulfide, and carbon disulfide|pmid=7152702 |doi=10.1007/bf00378410|bibcode=1982IAOEH..51...55H |s2cid=2768183 }}</ref> but the reports have not (as of 1995) been replicated.

===High-level exposure===
Short-term, high-level exposure can induce immediate collapse, with loss of breathing and a high probability of death. If death does not occur, high exposure to hydrogen sulfide can lead to [[Medicine:Cortical pseudolaminar necrosis|cortical pseudolaminar necrosis]], degeneration of the [[Biology:Basal ganglia|basal ganglia]] and [[Medicine:Cerebral edema|cerebral edema]].<ref name="pmid23111938"/> Although respiratory paralysis may be immediate, it can also be delayed up to 72 hours.<ref>{{cite web|url=http://www.firerescue1.com/fire-products/hazmat-equipment/articles/968922-The-chemical-suicide-phenomenon/ |title=The chemical suicide phenomenon |publisher=Firerescue1.com |date=2011-02-07 |access-date=2013-12-19}}</ref> Diagnostic of extreme poisoning by {{chem2|H2S}} is the discolouration of [[Chemistry:Copper|copper]] coins in the pockets of the victim.

Inhalation of {{chem2|H2S}} resulted in about 7 workplace deaths per year in the U.S. (2011–2017 data), second only to carbon monoxide (17 deaths per year) for workplace chemical inhalation deaths.<ref name='"BLS 2019"'>{{cite web |title=Fatal chemical inhalations in the workplace up in 2017 |url=https://www.bls.gov/opub/ted/2019/fatal-chemical-inhalations-in-the-workplace-up-in-2017.htm |publisher=U.S. Bureau of Labor Statistics |access-date=15 April 2022}}</ref>

====Exposure thresholds====

* Exposure limits stipulated by the United States government:<ref>{{Cite web|title=Hydrogen Sulfide - Hazards {{!}} Occupational Safety and Health Administration|url=https://www.osha.gov/hydrogen-sulfide/hazards|access-date=2021-09-27|website=www.osha.gov}}</ref>
**10 [[Parts per million|ppm]] [[Earth:Recommended exposure limit|REL]]-Ceiling ([[Organization:National Institute for Occupational Safety and Health|NIOSH]]): recommended permissible exposure ceiling (the recommended level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs)
**20 ppm [[Earth:Permissible exposure limit|PEL]]-Ceiling ([[Organization:Occupational Safety and Health Administration|OSHA]]): permissible exposure ceiling (the level that must not be exceeded, except once for 10 min. in an 8-hour shift, if no other measurable exposure occurs)
**50 ppm PEL-Peak (OSHA): peak permissible exposure (the level that must never be exceeded)
**100 ppm [[Chemistry:Immediately dangerous to life or health|IDLH]] (NIOSH): immediately dangerous to life and health (the level that interferes with the ability to escape)
* 0.00047&nbsp;ppm or 0.47&nbsp;ppb is the odor threshold, the point at which 50% of a human panel can detect the presence of an odor without being able to identify it.<ref name="IA State">{{cite web|author=Iowa State University Extension|date=May 2004|title=The Science of Smell Part 1: Odor perception and physiological response|url=http://www.extension.iastate.edu/Publications/PM1963A.pdf|access-date=2012-06-20|work=PM 1963a}}</ref>
* 10–20&nbsp;ppm is the borderline concentration for eye irritation.
* 50–100&nbsp;ppm leads to eye damage.
* At 100–150&nbsp;ppm the [[Biology:Olfactory nerve|olfactory nerve]] is paralyzed after a few inhalations, and the sense of smell disappears, often together with awareness of danger.<ref>USEPA; Health and Environmental Effects Profile for Hydrogen Sulfide p.118-8 (1980) ECAO-CIN-026A</ref><ref>{{cite book|last1=Zenz |first1=C. |first2=O.B. |last2=Dickerson |first3=E.P. |last3=Horvath |title=Occupational Medicine. |edition= 3rd |location=St. Louis, MO. |date=1994 |page=886}}</ref>
* 320–530&nbsp;ppm leads to [[Medicine:Pulmonary edema|pulmonary edema]] with the possibility of death.<ref name="pmid23111938"/>
* 530–1000&nbsp;ppm causes strong stimulation of the [[Biology:Central nervous system|central nervous system]] and rapid breathing, leading to loss of breathing.
* 800&nbsp;ppm is the lethal concentration for 50% of humans for 5 minutes' exposure (LC50).
* Concentrations over 1000&nbsp;ppm cause immediate collapse with loss of breathing, even after inhalation of a single breath.

====Treatment====

Treatment involves immediate inhalation of [[Chemistry:Amyl nitrite|amyl nitrite]], injections of [[Chemistry:Sodium nitrite|sodium nitrite]], or administration of 4-dimethylaminophenol in combination with inhalation of pure oxygen, administration of [[Medicine:Bronchodilator|bronchodilator]]s to overcome eventual bronchospasm, and in some cases hyperbaric oxygen therapy (HBOT).<ref name="pmid23111938"/> HBOT has clinical and anecdotal support.<ref>{{cite journal |last1=Gerasimon |first1=Gregg |last2=Bennett |first2=Steven |last3=Musser |first3=Jeffrey |last4=Rinard |first4=John |title=Acute hydrogen sulfide poisoning in a dairy farmer |journal=Clinical Toxicology |date=January 2007 |volume=45 |issue=4 |pages=420–423 |doi=10.1080/15563650601118010 |pmid=17486486 |s2cid=10952243 |url=https://zenodo.org/record/1234517 }}</ref><ref>{{cite journal |last1=Belley |first1=R. |last2=Bernard |first2=N. |last3=Côté |first3=M |last4=Paquet |first4=F. |last5=Poitras |first5=J. |title=Hyperbaric oxygen therapy in the management of two cases of hydrogen sulfide toxicity from liquid manure |journal=CJEM |volume=7 |issue=4 |pages=257–261 |date=July 2005 |pmid=17355683 |doi=10.1017/s1481803500014408 |doi-access=free }}</ref><ref>{{cite journal |last1=Hsu |first1=P |last2=Li |first2=H-W |last3=Lin |first3=Y-T |title=Acute hydrogen sulfide poisoning treated with hyperbaric oxygen. |journal=Journal of Hyperbaric Medicine |date=1987 |volume=2 |issue=4 |pages=215–221 |url=http://archive.rubicon-foundation.org/4354 |archive-url=https://web.archive.org/web/20081207074326/http://archive.rubicon-foundation.org/4354 |url-status=usurped |archive-date=December 7, 2008 }}</ref>

===Incidents===
Hydrogen sulfide was used by the British Army as a [[Chemistry:Chemical weapon|chemical weapon]] during [[Social:World War I|World War I]]. It was not considered to be an ideal war gas, partially due to its flammability and because the distinctive smell could be detected from even a small leak, alerting the enemy to the presence of the gas. It was nevertheless used on two occasions in 1916 when other gases were in short supply.<ref>{{cite book
| last = Foulkes
| first = Charles Howard
| title = "Gas!" The story of the special brigade
| publisher = Published by Naval & Military P.
| year = 2001
| orig-year = First published Blackwood & Sons, 1934
| isbn = 978-1-84342-088-0
| page = 105 }}</ref>

On September 2, 2005, a leak in the propeller room of a Royal Caribbean Cruise Liner docked in {{wipe|Los Angeles}} resulted in the deaths of 3 crewmen due to a [[Earth:Sewage|sewage]] line leak. As a result, all such compartments are now required to have a ventilation system.<ref>{{cite web |url=http://publichealth.lacounty.gov/acd/reports/spclrpts/spcrpt05/DeathsHydrogenSulfide05.pdf |website=County of Los Angeles: Department of Public Health |title=LA County Department of Public Health |access-date=2017-06-11 |archive-url=https://web.archive.org/web/20170218043631/http://publichealth.lacounty.gov/Acd/reports/spclrpts/spcrpt05/DeathsHydrogenSulfide05.pdf |archive-date=2017-02-18 |url-status=dead }}</ref><ref>{{cite news|title=Gas Kills 3 Crewmen on Ship |url=http://articles.latimes.com/2005/sep/03/local/me-port3 |newspaper=Los Angeles Times|date=2005-09-03 |last1=Becerra |first1=Hector |last2=Pierson |first2=David }}</ref>

A dump of toxic waste containing hydrogen sulfide is believed to have caused 17 deaths and thousands of illnesses in [[Place:Abidjan|Abidjan]], on the [[Place:West Africa|West African]] coast, in the 2006 Côte d'Ivoire toxic waste dump.

In September 2008, three workers were killed and two suffered serious injury, including long term brain damage, at a mushroom growing company in Langley, British Columbia. A valve to a pipe that carried chicken [[Chemistry:Manure|manure]], [[Biology:Straw|straw]] and [[Chemistry:Gypsum|gypsum]] to the compost fuel for the mushroom growing operation became clogged, and as workers unclogged the valve in a confined space without proper ventilation the hydrogen sulfide that had built up due to anaerobic decomposition of the material was released, poisoning the workers in the surrounding area.<ref>{{cite web|title=Details of Langley mushroom farm tragedy finally disclosed|url=https://www.abbynews.com/news/details-of-langley-mushroom-farm-tragedy-finally-disclosed/|first=Dan|last=Ferguson|publisher=Abbotsford News|date=September 16, 2011|access-date=April 13, 2020}}</ref> Investigator said there could have been more fatalities if the pipe had been fully cleared and/or if the wind had changed directions.<ref>{{cite news|title=Dozens could have died because of owner's negligence in B.C. mushroom farm incident: investigator|url=https://www.theglobeandmail.com/news/british-columbia/dozens-could-have-died-because-of-owners-negligence-in-bc-mushroom-farm-incident-investigator/article4106103/|work=The Canadian Press|publisher=The Globe and Mail|first=Terri|last=Theodore|date=May 8, 2012|access-date=April 13, 2020}}</ref>

In 2014, levels of hydrogen sulfide as high as 83&nbsp;ppm were detected at a recently built mall in Thailand called Siam Square One at the Siam Square area. Shop tenants at the mall reported health complications such as sinus inflammation, breathing difficulties and eye irritation. After investigation it was determined that the large amount of gas originated from imperfect treatment and disposal of waste water in the building.<ref>{{cite web|title=Do not breathe: Dangerous, toxic gas found at Siam Square One|url=http://bangkok.coconuts.co/2014/10/21/do-not-breathe-dangerous-toxic-gas-found-siam-square-one|website=Coconuts Bangkok|publisher=Coconuts Media |access-date=20 November 2014|date=2014-10-21}}</ref>

In 2014, hydrogen sulfide gas killed workers at the Promenade shopping center in North Scottsdale, Arizona, USA <ref>{{cite web | url=https://www.cbsnews.com/news/two-sewer-workers-die-apparently-due-to-toxic-fumes/ | title=Two sewer workers die, apparently due to toxic fumes - CBS News | website=CBS News | date=26 August 2014 }}</ref> after climbing into 15ft deep chamber without wearing [[Social:Personal protective equipment|personal protective gear]]. "Arriving crews recorded high levels of [[Chemistry:Hydrogen cyanide|hydrogen cyanide]] and hydrogen sulfide coming out of the sewer."

In November 2014, a substantial amount of hydrogen sulfide gas shrouded the central, eastern and southeastern parts of [[Place:Moscow|Moscow]]. Residents living in the area were urged to stay indoors by the emergencies ministry. Although the exact source of the gas was not known, blame had been placed on a Moscow oil refinery.<ref>{{cite news|title=Russian capital Moscow shrouded in noxious gas|url=https://www.bbc.com/news/world-europe-29990375|publisher=British Broadcasting Corporation|access-date=1 December 2014|work=BBC News|date=2014-11-10}}</ref>

In June 2016, a mother and her daughter were found dead in their still-running 2006 [[Engineering:Porsche Cayenne|Porsche Cayenne]] [[Engineering:SUV|SUV]] against a guardrail on Florida's Turnpike, initially thought to be victims of [[Medicine:Carbon monoxide poisoning|carbon monoxide poisoning]].<ref>{{cite news |title=Sources: Mom, daughter found dead in Porsche likely died from carbon monoxide |url=https://www.wftv.com/news/local/sources-mom-daughter-found-dead-in-porsche-likely-died-from-carbon-monoxide/328786342/ |work=WFTV |date=7 June 2016 |quote=Both had red skin and rash-like symptoms, and had vomited, sources said. }}</ref><ref name="Salinger">{{cite news|last1=Salinger|first1=Tobias|title=Woman, girl died after inhaling hydrogen sulfide, coroners say|url=http://www.nydailynews.com/news/national/woman-girl-died-inhaling-hydrogen-sulfide-coroners-article-1.2817657|access-date=28 April 2017|work=New York Daily News|date=4 October 2016}}</ref> Their deaths remained unexplained as the medical examiner waited for results of toxicology tests on the victims,<ref name="Lotan">{{cite news|last1=Lotan|first1=Gal Tziperman|title=Hydrogen sulfide inhalation killed mother, toddler found on Florida's Turnpike in June|url=http://www.orlandosentinel.com/news/breaking-news/os-latifa-lincoln-dead-hydrogen-sulfide-20161004-story.html|access-date=28 April 2017|work=Orlando Sentinel|date=4 October 2016}}</ref> until urine tests revealed that hydrogen sulfide was the cause of death. A report from the Orange-Osceola Medical Examiner's Office indicated that toxic fumes came from the Porsche's [[Engineering:Automotive battery|starter battery]], located under the front passenger seat.<ref>{{Cite web|url=http://www.wesh.com/news/medical-examiner-confirms-suspected-cause-of-deaths-in-turnpike-mystery/41939954|title=Medical examiner confirms suspected cause of deaths in Turnpike mystery|last=Kealing|first=Bob|access-date=2016-10-04|url-status=dead|archive-url=https://web.archive.org/web/20161005164308/http://www.wesh.com/news/medical-examiner-confirms-suspected-cause-of-deaths-in-turnpike-mystery/41939954|archive-date=2016-10-05}}</ref><ref>{{cite web|last1=Bell|first1=Lisa|others=Produced by Donovan Myrie |title=Hidden car dangers you should be aware of|url=https://www.clickorlando.com/news/investigators/hidden-car-dangers-you-should-be-aware-of |website=ClickOrlando.com |publisher=WKMG-TV|access-date=28 April 2017|date=19 March 2017|quote=Porsche Cayennes, along with a few other vehicles, have their batteries in the passenger compartment.}}</ref>

In January 2017, three utility workers in Key Largo, Florida, died one by one within seconds of descending into a narrow space beneath a [[Earth:Manhole cover|manhole cover]] to check a section of paved street.<ref>{{cite web|url=https://www.washingtonpost.com/amphtml/news/morning-mix/wp/2017/01/18/three-utility-workers-descend-to-their-deaths-in-florida-manhole-overcome-by-fumes/|archive-url=https://web.archive.org/web/20170118220358/https://www.washingtonpost.com/amphtml/news/morning-mix/wp/2017/01/18/three-utility-workers-descend-to-their-deaths-in-florida-manhole-overcome-by-fumes/|url-status=dead|archive-date=2017-01-18|title=One by one, 3 utility workers descended into a manhole. One by one, they died |website=www.washingtonpost.com}}</ref> In an attempt to save the men, a firefighter who entered the hole without his air tank (because he could not fit through the hole with it) collapsed within seconds and had to be rescued by a colleague.<ref name="Goodhue">{{cite news|last1=Goodhue|first1=David|title=Firefighter who tried to save 3 men in a manhole is fighting for his life|url=http://www.miamiherald.com/news/local/community/florida-keys/article126958804.html|access-date=28 April 2017|work=Miami Herald|date=17 January 2017}}</ref> The firefighter was airlifted to Jackson Memorial Hospital and later recovered.<ref>{{cite news |title=Key Largo firefighter takes first steps since nearly getting killed |url=https://wsvn.com/news/local/key-largo-firefighter-takes-first-steps-since-nearly-getting-killed/ |work=WSVN |date=18 January 2017 }}</ref><ref>{{cite news |title=Firefighter who survived Key Largo rescue attempt that killed 3 leaves hospital |url=https://www.sun-sentinel.com/news/florida/sfl-ap-key-largo-firefighter-recovering-20170126-story.html |work=Sun Sentinel |agency=The Associated Press |date=26 January 2017 }}</ref> A Monroe County Sheriff officer initially determined that the space contained hydrogen sulfide and [[Chemistry:Methane|methane]] gas produced by decomposing vegetation.<ref name="Rabin">{{cite news|last1=Rabin|first1=Charles|last2=Goodhue|first2=David|title=Three Keys utility workers die in wastewater trench|url=http://www.miamiherald.com/news/local/community/florida-keys/article126799319.html|access-date=28 April 2017|work=Miami Herald|date=16 January 2017}}</ref>

On May 24, 2018, two workers were killed, another seriously injured, and 14 others hospitalized by hydrogen sulfide inhalation at a Norske Skog paper mill in Albury, New South Wales.<ref name="Clantar 2020">{{cite news |last=Clantar |first=Claire |title=Former Victorian paper mill fined $1 million after deaths of two workers |work=9News |date=25 Sep 2020 |url=https://www.9news.com.au/national/norske-skog-paper-mill-1-million-fine-after-deaths-of-two-employees/2320f231-debc-4ae4-9fae-e4933bbb9c8b |access-date=30 May 2021}}</ref><ref>{{cite news |author=<!--Staff writer(s)/no by-line.--> |title=Two fatalities in suspected hydrogen sulfide gas leak at paper mill |work=Australian Institute of Health & Safety |date=31 May 2018 |url=https://www.aihs.org.au/news-and-publications/news/two-fatalities-in-suspected-hydrogen-sulfide-gas-leak-paper-mill |access-date=30 May 2021}}</ref> An investigation by [[Organization:Safe Work Australia|SafeWork NSW]] found that the gas was released from a tank used to hold process water. The workers were exposed at the end of a 3-day maintenance period. Hydrogen sulfide had built up in an upstream tank, which had been left stagnant and untreated with [[Biology:Biocide|biocide]] during the maintenance period. These conditions allowed sulfate-reducing bacteria to grow in the upstream tank, as the water contained small quantities of [[Chemistry:Pulp (paper)#Wood pulp|wood pulp]] and [[Chemistry:Wood fibre|fiber]]. The high rate of pumping from this tank into the tank involved in the incident caused hydrogen sulfide gas to escape from various openings around its top when pumping was resumed at the end of the maintenance period. The area above it was sufficiently enclosed for the gas to pool there, despite not being identified as a confined space by Norske Skog. One of the workers who was killed was exposed while investigating an apparent fluid leak in the tank, while the other who was killed and the worker who was badly injured were attempting to rescue the first after he collapsed on top of it. In a resulting criminal case, Norske Skog was accused of failing to ensure the health and safety of its workforce at the plant to a reasonably practicable extent. It pleaded guilty, and was fined AU$1,012,500 and ordered to fund the production of an anonymized educational video about the incident.<ref>{{cite news |last=Brescia |first=Paul |title=SafeWork investigating Norske Skog |work=Sprinter |date=28 May 2018 |url=https://www.sprinter.com.au/safework-investigating-norske-skog/ |access-date=30 May 2021}}</ref><ref>{{cite court |litigants=SafeWork NSW v Norske Skog Paper Mills (Australia) Limited |court=District Court of New South Wales |reporter=NSWDC 559 |date=25 September 2020 |url=https://www.caselaw.nsw.gov.au/decision/174be35ee49dc41d188b23cd |access-date=30 May 2021}}</ref><ref name="Clantar 2020" /><ref>{{cite AV media |author=SafeWork NSW |title=Incident Animation – Hazardous Gas |type=Motion picture |date=29 Mar 2021 |url=https://www.youtube.com/watch?v=bo2XN43lXAc | archive-url=https://ghostarchive.org/varchive/youtube/20211030/bo2XN43lXAc| archive-date=2021-10-30|access-date=30 May 2021}}{{cbignore}}</ref>

In October 2019, an Odessa, Texas employee of Aghorn Operating Inc. and his wife were killed due to a water pump failure. [[Earth:Produced water|Produced water]] with a high concentration of hydrogen sulfide was released by the pump. The worker died while responding to an automated phone call he had received alerting him to a mechanical failure in the pump, while his wife died after driving to the facility to check on him.<ref>{{cite news |author=<!--Staff writer(s)/no by-line.--> |title=Feds Probe Fatal 2019 Hydrogen Sulfide Release in Texas |work=Industrial Fire World |date=27 July 2020 |url=https://www.industrialfireworld.com/566266/feds-probe-fatal-2019-hydrogen-sulfide-release-in-texas |access-date=29 May 2021 }}</ref> A [[Chemistry:U.S. Chemical Safety and Hazard Investigation Board|CSB]] investigation cited lax safety practices at the facility, such as an informal [[Engineering:Lockout-tagout|lockout-tagout]] procedure and a nonfunctioning hydrogen sulfide alert system.<ref>{{cite web |url=https://www.csb.gov/aghorn-operating-waterflood-station-hydrogen-sulfide-release-/ |title=Aghorn Operating Waterflood Station Hydrogen Sulfide Release |publisher=U.S. Chemical Safety and Hazardous Investigation Board |author=<!--Staff writer(s); no by-line.--> |date=21 May 2021 |access-date=29 May 2021}}</ref>

===Suicides===
The gas, produced by mixing certain household ingredients, was used in a [[Medicine:Suicide|suicide]] wave in 2008 in Japan.<ref>{{Cite magazine|url=https://www.wired.com/threatlevel/2009/03/japanese-deterg/|title=Dangerous Japanese 'Detergent Suicide' Technique Creeps Into U.S|date=March 13, 2009|magazine=Wired}}</ref> The wave prompted staff at Tokyo's suicide prevention center to set up a special hotline during "Golden Week", as they received an increase in calls from people wanting to kill themselves during the annual May holiday.<ref>{{cite news |last1=Namiki |first1=Noriko |title=Terrible Twist in Japan Suicide Spates |url=https://abcnews.go.com/Health/story?id=4908320 |work=ABC News |date=23 May 2008 }}</ref>

As of 2010, this phenomenon has occurred in a number of US cities, prompting warnings to those arriving at the site of the suicide.<ref>http://info.publicintelligence.net/LARTTAChydrogensulfide.pdf{{full citation needed|date=September 2020}}</ref><ref>http://info.publicintelligence.net/MAchemicalsuicide.pdf{{full citation needed|date=September 2020}}</ref><ref>http://info.publicintelligence.net/illinoisH2Ssuicide.pdf{{full citation needed|date=September 2020}}</ref><ref>http://info.publicintelligence.net/NYhydrogensulfide.pdf{{full citation needed|date=September 2020}}</ref><ref>http://info.publicintelligence.net/KCTEWhydrogensulfide.pdf{{full citation needed|date=September 2020}}</ref> These first responders, such as emergency services workers or family members are at risk of death or injury from inhaling the gas, or by fire.<ref>{{Cite web|title=Chemical Suicide on Campus |website=www.maryland.gov |url=https://www.maryland.gov/Pages/default.aspx |archiveurl=https://web.archive.org/web/20120103193036/http://www.dhmh.maryland.gov/suicideprevention/safety%20alert.pdf|archivedate=January 3, 2012 |url-status=dead}}</ref><ref>{{cite web |title=Chemical Suicides |url=http://www.policemag.com/Channel/Patrol/Articles/Print/Story/2011/04/Duty-Dangers-Chemical-Suicides.aspx |last=Scoville |first=Dean |publisher=POLICE Magazine |date=April 2011 |access-date=2013-12-19}}</ref> Local governments have also initiated campaigns to prevent such suicides.

In 2020, {{chem2|H2S}} ingestion was used as a suicide method by Japanese pro wrestler Hana Kimura.<ref>{{cite news |url=https://comicbook.com/wwe/news/hana-kimura-cause-of-death-suicide-hydrogen-sulfide-suicide-wwe-stardom/ |title=Hana Kimura Cause Of Death Revealed |work=ComicBook.com |first=Connor |last=Casey |date=26 May 2020 |quote=More details about her death have since come to light, as Dave Meltzer provided details about what happened on the night of her death during a recent Wrestling Observer Radio. According to Meltzer, Kimura died after inhalation of hydrogen sulfide. He explained that concerns about her health first popped up when she posted a tweet early Saturday morning indicating that she was going to cause self-harm.}}</ref>

==Hydrogen sulfide in the natural environment==
===Microbial: The sulfur cycle===
{{Anchor|Microbial|Sulfur cycle}}
{{main|Biology:Sulfur cycle}}
[[File:Teichschlamm1.jpg|thumb|left|[[Engineering:Sludge|Sludge]] from a pond; the black color is due to metal sulfides]]

Hydrogen sulfide is a central participant in the [[Biology:Sulfur cycle|sulfur cycle]], the [[Biology:Biogeochemical cycle|biogeochemical cycle]] of sulfur on Earth.<ref>{{cite book |doi=10.1007/978-94-017-9269-1_10 |chapter=Hydrogen Sulfide: A Toxic Gas Produced by Dissimilatory Sulfate and Sulfur Reduction and Consumed by Microbial Oxidation |title=The Metal-Driven Biogeochemistry of Gaseous Compounds in the Environment |series=Metal Ions in Life Sciences |year=2014 |last1=Barton |first1=Larry L. |last2=Fardeau |first2=Marie-Laure |last3=Fauque |first3=Guy D. |volume=14 |pages=237–277 |pmid=25416397 |isbn=978-94-017-9268-4 }}</ref>

In the absence of [[Chemistry:Oxygen|oxygen]], [[Biology:Sulfur-reducing bacteria|sulfur-reducing]] and sulfate-reducing bacteria derive energy from [[Chemistry:Redox|oxidizing]] hydrogen or organic molecules by reducing elemental sulfur or sulfate to hydrogen sulfide. Other bacteria liberate hydrogen sulfide from sulfur-containing [[Chemistry:Amino acid|amino acid]]s; this gives rise to the odor of rotten eggs and contributes to the odor of [[Medicine:Flatulence|flatulence]].

As organic matter decays under low-oxygen (or [[Earth:Hypoxia (environmental)|hypoxic]]) conditions (such as in swamps, eutrophic lakes or [[Earth:Dead zone (ecology)|dead zones]] of oceans), sulfate-reducing bacteria will use the sulfates present in the water to oxidize the organic matter, producing hydrogen sulfide as waste. Some of the hydrogen sulfide will react with metal ions in the water to produce metal sulfides, which are not water-soluble. These metal sulfides, such as ferrous sulfide FeS, are often black or brown, leading to the dark color of [[Engineering:Sludge|sludge]].

Several groups of bacteria can use hydrogen sulfide as fuel, oxidizing it to elemental sulfur or to sulfate by using dissolved oxygen, metal oxides (e.g., [[Chemistry:Iron(III) oxide-hydroxide|iron oxyhydroxides]] and [[Chemistry:Manganese oxide|manganese oxide]]s), or nitrate as electron acceptors.<ref>{{cite book|last1=Jørgensen |first1=B. B. |first2=D. C. |last2=Nelson |date=2004 |chapter=Sulfide oxidation in marine sediments: Geochemistry meets microbiology |pages=36–81 |editor1-first=J. P. |editor1-last=Amend |editor2-first=K. J. |editor2-last=Edwards |editor3-first=T. W. |editor3-last=Lyons |title=Sulfur Biogeochemistry – Past and Present |publisher=Geological Society of America}}</ref>

The [[Biology:Purple sulfur bacteria|purple sulfur bacteria]] and the [[Biology:Green sulfur bacteria|green sulfur bacteria]] use hydrogen sulfide as an [[Chemistry:Electron donor|electron donor]] in [[Earth:Photosynthesis|photosynthesis]], thereby producing elemental sulfur. This mode of photosynthesis is older than the mode of [[Biology:Cyanobacteria|cyanobacteria]], [[Biology:Algae|algae]], and [[Biology:Plant|plant]]s, which uses water as electron donor and liberates oxygen.

The biochemistry of hydrogen sulfide is a key part of the chemistry of the iron-sulfur world. In this model of the origin of life on Earth, geologically produced hydrogen sulfide is postulated as an electron donor driving the reduction of carbon dioxide.<ref>{{cite journal |last1=Wächtershäuser |first1=G |title=Before enzymes and templates: theory of surface metabolism. |journal=Microbiological Reviews |date=December 1988 |volume=52 |issue=4 |pages=452–484 |doi=10.1128/MMBR.52.4.452-484.1988 |pmid=3070320 |pmc=373159 }}</ref>

===Animals===
Hydrogen sulfide is lethal to most animals, but a few highly specialized species ([[Earth:Extremophile|extremophile]]s) do thrive in habitats that are rich in this compound.<ref name=Tobler2008>{{cite journal |last1=Tobler |first1=M |last2=Riesch |first2=R. |last3=García de León |first3=F. J. |last4=Schlupp |first4=I. |last5=Plath |first5=M. |date=2008 |title=Two endemic and endangered fishes, ''Poecilia sulphuraria'' (Álvarez, 1948) and ''Gambusia eurystoma'' Miller, 1975 (Poeciliidae, Teleostei) as only survivors in a small sulphidic habitat |journal=Journal of Fish Biology |volume=72 |issue=3 |pages=523–533 |doi=10.1111/j.1095-8649.2007.01716.x |bibcode=2008JFBio..72..523T |s2cid=27303725 }}</ref>

In the deep sea, [[Earth:Hydrothermal vent|hydrothermal vent]]s and [[Earth:Cold seep|cold seep]]s with high levels of hydrogen sulfide are home to a number of extremely specialized lifeforms, ranging from bacteria to fish.{{which|date=June 2015}}<ref>{{cite journal|last1=Bernardino|first1=Angelo F. |last2=Levin|first2=Lisa A. |last3=Thurber|first3=Andrew R. |last4=Smith|first4=Craig R. |date=2012 |title=Comparative Composition, Diversity and Trophic Ecology of Sediment Macrofauna at Vents, Seeps and Organic Falls. |journal=PLOS ONE |volume=7|issue=4|page=e33515|doi=10.1371/journal.pone.0033515 |pmid=22496753 |pmc=3319539|bibcode=2012PLoSO...733515B|doi-access=free }}</ref> Because of the absence of sunlight at these depths, these ecosystems rely on [[Earth:Chemosynthesis|chemosynthesis]] rather than [[Earth:Photosynthesis|photosynthesis]].<ref>{{cite web|work=Marine Society of Australia|url=http://www.mesa.edu.au/deep_sea/hydrothermal_vents.asp|title=Hydrothermal Vents|access-date=28 December 2014}}</ref>

Freshwater springs rich in hydrogen sulfide are mainly home to invertebrates, but also include a small number of fish: ''Cyprinodon bobmilleri'' (a [[Biology:Pupfish|pupfish]] from Mexico), ''[[Biology:Limia sulphurophila|Limia sulphurophila]]'' (a poeciliid from the Dominican Republic), ''Gambusia eurystoma'' (a poeciliid from Mexico), and a few ''[[Biology:Poecilia|Poecilia]]'' (poeciliids from Mexico).<ref name=Tobler2008/><ref>{{cite journal|last1=Palacios|first1=Maura |last2=Arias-Rodríguez|first2=Lenín |last3=Plath|first3=Martin |last4=Eifert|first4=Constanze |last5=Lerp|first5=Hannes |last6=Lamboj|first6=Anton |last7=Voelker |first7=Gary|last8=Tobler|first8=Michael |date=2013 |title=The Rediscovery of a Long Described Species Reveals Additional Complexity in Speciation Patterns of Poeciliid Fishes in Sulfide Springs.|journal=PLOS ONE |volume=8|issue=8 |page=e71069|doi=10.1371/journal.pone.0071069 |pmid=23976979 |pmc=3745397|bibcode=2013PLoSO...871069P|doi-access=free }}</ref> Invertebrates and microorganisms in some cave systems, such as [[Earth:Movile Cave|Movile Cave]], are adapted to high levels of hydrogen sulfide.<ref>{{cite journal |last1=Kumaresan |first1=Deepak |last2=Wischer |first2=Daniela |last3=Stephenson |first3=Jason |last4=Hillebrand-Voiculescu |first4=Alexandra |last5=Murrell |first5=J. Colin |title=Microbiology of Movile Cave—A Chemolithoautotrophic Ecosystem |journal=Geomicrobiology Journal |date=16 March 2014 |volume=31 |issue=3 |pages=186–193 |doi=10.1080/01490451.2013.839764 |bibcode=2014GmbJ...31..186K |s2cid=84472119 }}</ref>

===Interstellar and planetary occurrence===
Hydrogen sulfide has often been detected in the interstellar medium.<ref>{{cite journal |last1=Despois |first1=D. |title=Radio Line Observations Of Molecular And Isotopic Species In Comet C/1995 O1 (Hale-Bopp) |journal=Earth, Moon, and Planets |date=1997 |volume=79 |issue=1/3 |pages=103–124 |doi=10.1023/A:1006229131864 |bibcode=1997EM&P...79..103D |s2cid=118540103 }}</ref> It also occurs in the clouds of planets in our solar system.<ref>{{cite journal |last1=Irwin |first1=Patrick G. J. |last2=Toledo |first2=Daniel |last3=Garland |first3=Ryan |last4=Teanby |first4=Nicholas A. |last5=Fletcher |first5=Leigh N. |last6=Orton |first6=Glenn A. |last7=Bézard |first7=Bruno |title=Detection of hydrogen sulfide above the clouds in Uranus's atmosphere |journal=Nature Astronomy |date=May 2018 |volume=2 |issue=5 |pages=420–427 |doi=10.1038/s41550-018-0432-1 |bibcode=2018NatAs...2..420I |hdl=2381/42547 |s2cid=102775371 |url=https://research-information.bris.ac.uk/en/publications/detection-of-hydrogen-sulfide-above-the-clouds-in-uranuss-atmosphere(099d2fdd-8d3d-4e78-b009-bebffdece302).html |hdl-access=free }}</ref><ref name=lissauer2019>{{Cite book |title=Fundamental Planetary Sciences : physics, chemistry, and habitability |last1=Lissauer|first1=Jack J. |last2=de Pater|first2=Imke |year=2019 |publisher=Cambridge University Press |pages=149–152|isbn=9781108411981 |location=New York, NY, USA }}{{page needed|date=September 2020}}</ref>

===Mass extinctions===
{{main|Earth:Anoxic event}}
[[File:Hydrogen Sulfide Emissions off of Africa.jpg|thumb|A hydrogen sulfide bloom (green) stretching for about 150km along the coast of Namibia. As oxygen-poor water reaches the coast, bacteria in the organic-matter rich sediment produce hydrogen sulfide, which is toxic to fish.]]
Hydrogen sulfide has been implicated in several [[Biology:Extinction event|mass extinctions]] that have occurred in the Earth's past. In particular, a buildup of hydrogen sulfide in the atmosphere may have caused, or at least contributed to, the Permian-Triassic extinction event 252 million years ago.<ref name="sciam" /><ref>{{cite journal |last1=Lamarque |first1=J.-F. |last2=Kiehl |first2=J. T. |last3=Orlando |first3=J. J. |date=16 January 2007 |title=Role of hydrogen sulfide in a Permian-Triassic boundary ozone collapse |journal=[[Earth:Geophysical Research Letters|Geophysical Research Letters]] |volume=34 |issue=2 |pages=1–4 |doi=10.1029/2006GL028384 |bibcode=2007GeoRL..34.2801L |s2cid=55812439 |doi-access=free }}</ref><ref name=Kump2005>{{cite journal |last1=Kump |first1=Lee |last2=Pavlov |first2=Alexander |first3=Michael A. |last3=Arthur |title=Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia |journal=Geology |date=1 May 2005 |volume=33 |issue=5 |pages=397–400 |url=https://www.researchgate.net/publication/253144294 |doi=10.1130/G21295.1 |bibcode=2005Geo....33..397K |access-date=2 April 2023}}</ref>

Organic residues from these extinction boundaries indicate that the oceans were anoxic (oxygen-depleted) and had species of shallow plankton that metabolized {{chem2|H2S}}. The formation of {{chem2|H2S}} may have been initiated by massive volcanic eruptions, which emitted [[Chemistry:Carbon dioxide|carbon dioxide]] and [[Chemistry:Methane|methane]] into the atmosphere, which warmed the oceans, lowering their capacity to absorb oxygen that would otherwise oxidize {{chem2|H2S}}. The increased levels of hydrogen sulfide could have killed oxygen-generating plants as well as depleted the ozone layer, causing further stress. Small {{chem2|H2S}} blooms have been detected in modern times in the [[Earth:Dead Sea|Dead Sea]] and in the Atlantic ocean off the coast of Namibia.<ref name="sciam">{{cite magazine|url=http://www.sciam.com/article.cfm?articleID=00037A5D-A938-150E-A93883414B7F0000&sc=I100322|title=Impact from the Deep|magazine=Scientific American | date = October 2006 }}</ref>

==See also==<!-- Please respect alphabetical order -->
*{{annotated link|Chemistry:Hydrogen chalcogenide}}
*[[Biology:Hydrogen sulfide chemosynthesis|Hydrogen sulfide chemosynthesis]]
*{{annotated link|Engineering:Sewer gas}}
*{{annotated link|Biology:Targeted temperature management|aka=induced hypothermia}}
*[[Physics:Marsh gas|Marsh gas]]

==References==
{{Reflist|30em}}

== Additional resources ==
*{{cite book|title=Hydrogen Sulfide|author=Committee on Medical and Biological Effects of Environmental Pollutants|publisher=University Park Press|date=1979|location=Baltimore|isbn=978-0-8391-0127-7}}
*{{cite thesis|degree=MS|last=Siefers|first=Andrea|title=A novel and cost-effective hydrogen sulfide removal technology using tire derived rubber particles|publisher=Iowa State University|year=2010|url=http://lib.dr.iastate.edu/etd/11281/|access-date=8 February 2013}}

==External links==
* [http://www.inchem.org/documents/icsc/icsc/eics0165.htm International Chemical Safety Card 0165]
* [http://www.inchem.org/documents/cicads/cicads/cicad53.htm Concise International Chemical Assessment Document 53]
* [https://web.archive.org/web/20060309114102/http://www.npi.gov.au/database/substance-info/profiles/49.html National Pollutant Inventory - Hydrogen sulfide fact sheet]
* [https://www.cdc.gov/niosh/npg/npgd0337.html NIOSH Pocket Guide to Chemical Hazards]
* [https://www.nace.org/ NACE (National Association of Corrosion Epal)]
{{Chemical agents}}
{{Hydrogen compounds}}
{{Neurotransmitters}}
{{Sulfur compounds}}
{{Molecules detected in outer space}}
{{Hydrides by group}}


{{DEFAULTSORT:Hydrogen Sulfide}}
[[Category:Acids]]
[[Category:Foul-smelling chemicals]]
[[Category:Hydrogen compounds]]
[[Category:Triatomic molecules]]
[[Category:Industrial gases]]
[[Category:Sulfides]]
[[Category:Flatulence]]
[[Category:Gaseous signaling molecules]]

{{Sourceattribution|Hydrogen sulfide}}