Editing Formaldehyde (section)

==Occurrence==
Processes in the upper [[Earth's atmosphere|atmosphere]] contribute more than 80% of the total formaldehyde in the environment.<ref>{{Cite journal |last1=Luecken |first1=D. J. |last2=Hutzell |first2=W. T. |last3=Strum |first3=M. L. |last4=Pouliot |first4=G. A. |date=2012-02-01 |title=Regional sources of atmospheric formaldehyde and acetaldehyde, and implications for atmospheric modeling |url=https://www.sciencedirect.com/science/article/pii/S1352231011010508 |journal=Atmospheric Environment |volume=47 |pages=477–490 |doi=10.1016/j.atmosenv.2011.10.005 |bibcode=2012AtmEn..47..477L |issn=1352-2310|url-access=subscription }}</ref> Formaldehyde is an intermediate in the oxidation (or [[combustion]]) of [[methane]], as well as of other carbon compounds, e.g. in [[forest fire]]s, [[automobile]] exhaust, and [[tobacco smoke]]. When produced in the atmosphere by the action of sunlight and [[oxygen]] on [[atmospheric methane]] and other [[hydrocarbon]]s, it becomes part of [[smog]]. Formaldehyde has also been detected in outer space.

Formaldehyde and its [[adducts]] are ubiquitous in nature. Food may contain formaldehyde at levels 1–100&nbsp;mg/kg.<ref>{{Cite book |title=Air Quality Guidelines |publisher=WHO Regional Office for Europe |year=2001 |edition=2nd |location=Copenhagen, Denmark |language=en |chapter=Chapter 5.8 Formaldehyde |chapter-url=https://intranet.euro.who.int/__data/assets/pdf_file/0014/123062/AQG2ndEd_5_8Formaldehyde.pdf |access-date=2023-02-18 |archive-date=2023-02-18 |archive-url=https://web.archive.org/web/20230218053951/https://intranet.euro.who.int/__data/assets/pdf_file/0014/123062/AQG2ndEd_5_8Formaldehyde.pdf |url-status=live}}</ref> Formaldehyde, formed in the metabolism of the amino acids [[serine]] and [[threonine]], is found in the bloodstream of humans and other primates at concentrations of approximately 50&nbsp;[[micromolar]].<ref name=Chang>{{cite journal |doi=10.1126/science.abp9201 |title=Formaldehyde regulates ''S'' -adenosylmethionine biosynthesis and one-carbon metabolism |date=2023 |last1=Pham |first1=Vanha N. |last2=Bruemmer |first2=Kevin J. |last3=Toh |first3=Joel D. W. |last4=Ge |first4=Eva J. |last5=Tenney |first5=Logan |last6=Ward |first6=Carl C. |last7=Dingler |first7=Felix A. |last8=Millington |first8=Christopher L. |last9=Garcia-Prieto |first9=Carlos A. |last10=Pulos-Holmes |first10=Mia C. |last11=Ingolia |first11=Nicholas T. |last12=Pontel |first12=Lucas B. |last13=Esteller |first13=Manel |last14=Patel |first14=Ketan J. |last15=Nomura |first15=Daniel K. |last16=Chang |first16=Christopher J. |journal=Science |volume=382 |issue=6670 |pages=eabp9201 |pmid=37917677 |bibcode=2023Sci...382P9201P |s2cid=264935787|pmc=11500418 }}</ref> Experiments in which animals are exposed to an atmosphere containing isotopically labeled formaldehyde have demonstrated that even in deliberately exposed animals, the majority of formaldehyde-DNA adducts found in non-respiratory tissues are derived from endogenously produced formaldehyde.<ref>{{cite journal |doi=10.1093/toxsci/kfq371 |title=Endogenous versus Exogenous DNA Adducts: Their Role in Carcinogenesis, Epidemiology, and Risk Assessment |year=2011 |last1=Swenberg |first1=J. A. |last2=Lu |first2=K. |last3=Moeller |first3=B. C. |last4=Gao |first4=L. |last5=Upton |first5=P. B. |last6=Nakamura |first6=J. |last7=Starr |first7=T. B. |journal=Toxicological Sciences |volume=120 |issue=Suppl 1 |pages=S130–S145 |pmid=21163908 |pmc=3043087}}</ref>

Formaldehyde does not accumulate in the environment, because it is broken down within a few hours by sunlight or by bacteria present in soil or water. Humans metabolize formaldehyde quickly, converting it to [[formic acid]].<ref>{{cite press release | date = 2014-01-29 | title = Formaldehyde Is Biodegradable, Quickly Broken Down in the Air By Sunlight or By Bacteria in Soil or Water | url = https://www.americanchemistry.com/Media/PressReleasesTranscripts/ACC-news-releases/Formaldehyde-Is-Biodegradable.html | publisher = Formaldehyde Panel of the American Chemistry Council | access-date = 2017-04-22 | archive-url = https://web.archive.org/web/20190328042754/https://www.americanchemistry.com/Media/PressReleasesTranscripts/ACC-news-releases/Formaldehyde-Is-Biodegradable.html | archive-date = 2019-03-28 | url-status = dead}}</ref><ref>{{Cite web |date=2019-03-28 |title=Toxicological Profile for Formaldehyde |url=https://www.atsdr.cdc.gov/ToxProfiles/tp111.pdf |archive-url=https://web.archive.org/web/20190328010414/https://www.atsdr.cdc.gov/ToxProfiles/tp111.pdf |archive-date=2019-03-28 |access-date=2023-02-18}}</ref> It nonetheless presents [[#Safety|significant health concerns]], as a [[contaminant]].

===Interstellar formaldehyde===
{{Main|Interstellar formaldehyde}}
Formaldehyde appears to be a useful probe in astrochemistry due to prominence of the 1<sub>10</sub>←1<sub>11</sub> and 2<sub>11</sub>←2<sub>12</sub> ''K''-doublet transitions. It was the first polyatomic [[Organic chemistry|organic]] molecule detected in the [[interstellar medium]].<ref>{{cite journal|last1=Zuckerman|first1=B.|last2=Buhl|first2=D.|last3=Palmer|first3=P.|last4=Snyder|first4=L. E.|year=1970|title=Observation of interstellar formaldehyde|journal=Astrophys. J.|volume=160|pages=485–506|doi=10.1086/150449|bibcode=1970ApJ...160..485Z}}</ref> Since its initial detection in 1969, it has been observed in many regions of the [[Milky Way galaxy|galaxy]]. Because of the widespread interest in interstellar formaldehyde, it has been extensively studied, yielding new extragalactic sources.<ref name="mangum">{{cite journal|first1=Jeffrey G.|last1=Mangum|first2=Jeremy|last2=Darling|first3=Karl M.|last3=Menten|first4=Christian|last4=Henkel|s2cid=14035123|year=2008|title=Formaldehyde Densitometry of Starburst Galaxies|journal=Astrophys. J.|volume=673|issue=2|pages=832–46|doi=10.1086/524354|bibcode=2008ApJ...673..832M |arxiv = 0710.2115}}</ref> A proposed mechanism for the formation is the hydrogenation of CO ice:<ref name="Woon">{{cite journal|last=Woon|first=David E.|year=2002|title=Modeling Gas-Grain Chemistry with Quantum Chemical Cluster Calculations. I. Heterogeneous Hydrogenation of CO and H<sub>2</sub>CO on Icy Grain Mantles|journal=Astrophys. J.|volume=569|issue=1|pages=541–48|doi=10.1086/339279|bibcode=2002ApJ...569..541W |doi-access=free}}</ref>
: H + CO → HCO
: HCO + H → CH<sub>2</sub>O

[[Hydrogen cyanide|HCN]], [[Hydrogen isocyanide|HNC]], H<sub>2</sub>CO, and [[dust]] have also been observed inside the [[Coma (cometary)|comae]] of [[comet]]s [[C/2012 F6 (Lemmon)]] and [[Comet ISON|C/2012 S1 (ISON)]].<ref name="NASA-20140811">{{cite web |last1=Zubritsky |first1=Elizabeth |last2=Neal-Jones |first2=Nancy |title=RELEASE 14-038 - NASA's 3-D Study of Comets Reveals Chemical Factory at Work |url=http://www.nasa.gov/press/2014/august/goddard/nasa-s-3-d-study-of-comets-reveals-chemical-factory-at-work |date=11 August 2014 |work=[[NASA]] |access-date=12 August 2014 |archive-date=12 August 2014 |archive-url=https://web.archive.org/web/20140812210755/http://www.nasa.gov/press/2014/august/goddard/nasa-s-3-d-study-of-comets-reveals-chemical-factory-at-work |url-status=live}}</ref><ref name="AJL-20140811">{{cite journal |author=Cordiner, M.A. |s2cid=26277035 |title=Mapping the Release of Volatiles in the Inner Comae of Comets C/2012 F6 (Lemmon) and C/2012 S1 (ISON) Using the Atacama Large Millimeter/Submillimeter Array |date=11 August 2014 |journal=[[The Astrophysical Journal]] |volume=792 |number=1 |doi=10.1088/2041-8205/792/1/L2 |display-authors=etal |pages=L2 |bibcode=2014ApJ...792L...2C|arxiv=1408.2458}}</ref>