Organophosphate: Difference between revisions

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===Water solubility===
===Water solubility===
The water solubility of organophosphates is important factor is important in biological, industrial and environmental settings. The wide variety of substitutes used in organophosphate esters results in great variations in physical properties. OPEs exhibit a wide range of octanol/water [[partition coefficient]]s where log Kow values range from -0.98 up to 10.6.<ref name=":4" /> The majority of OPEs used as flame retardants and plasticisers are tri-esters with positive log Kow values ranging between 1.44 and 9.49, signifying [[hydrophobicity]].<ref name=":4" /><ref>{{cite journal |last1=Möller |first1=A. |last2=Sturm |first2=R. |last3=Xie |first3=Z. |last4=Cai |first4=M. |last5=He |first5=J. |last6=Ebinghaus |first6=R. |date=2012 |title=Organophosphorus Flame Retardants and Plasticizers in Airborne Particles over the Northern Pacific and Indian Ocean toward the Polar Regions: Evidence for Global Occurrence |url=https://doi.org/10.1021/es204272v |journal=Environmental Science and Technology |volume=46 |issue=6 |pages=3127–3134 | pmid=22332897 | doi=10.1021/es204272v|bibcode=2012EnST...46.3127M }}</ref><ref name=":6" /><ref name=":7" /> Hydrophobic OPEs are more likely to be bioaccumulated and biomagnified in aquatic ecosystems.<ref name=":5" /> Halogenated organophosphates tend to be denser than water and sink, causing them to accumulate in sediments.<ref>{{Cite journal|last1=McDonough|first1=Carrie A.|last2=De Silva|first2=Amila O.|last3=Sun|first3=Caoxin|last4=Cabrerizo|first4=Ana|last5=Adelman|first5=David|last6=Soltwedel|first6=Thomas|last7=Bauerfeind|first7=Eduard|last8=Muir|first8=Derek C. G.|last9=Lohmann|first9=Rainer|date=2018-06-05|title=Dissolved Organophosphate Esters and Polybrominated Diphenyl Ethers in Remote Marine Environments: Arctic Surface Water Distributions and Net Transport through Fram Strait|url=https://pubs.acs.org/doi/10.1021/acs.est.8b01127|journal=Environmental Science & Technology|language=en|volume=52|issue=11|pages=6208–6216|doi=10.1021/acs.est.8b01127|pmid=29787253|bibcode=2018EnST...52.6208M|issn=0013-936X}}</ref>
The water solubility of organophosphates is important factor is important in biological, industrial and environmental settings. The wide variety of substitutes used in organophosphate esters results in great variations in physical properties. OPEs exhibit a wide range of octanol/water [[partition coefficient]]s where log Kow values range from -0.98 up to 10.6.<ref name=":4" /> The majority of OPEs used as flame retardants and plasticisers are tri-esters with positive log Kow values ranging between 1.44 and 9.49, signifying [[hydrophobicity]].<ref name=":4" /><ref>{{cite journal |last1=Möller |first1=A. |last2=Sturm |first2=R. |last3=Xie |first3=Z. |last4=Cai |first4=M. |last5=He |first5=J. |last6=Ebinghaus |first6=R. |date=2012 |title=Organophosphorus Flame Retardants and Plasticizers in Airborne Particles over the Northern Pacific and Indian Ocean toward the Polar Regions: Evidence for Global Occurrence |url=https://doi.org/10.1021/es204272v |journal=Environmental Science and Technology |volume=46 |issue=6 |pages=3127–3134 | pmid=22332897 | doi=10.1021/es204272v|bibcode=2012EnST...46.3127M }}</ref><ref name=":6" /><ref name=":7">{{cite journal |last1=Greaves |first1=Alana K. |last2=Letcher |first2=Robert J. |title=A Review of Organophosphate Esters in the Environment from Biological Effects to Distribution and Fate |journal=Bulletin of Environmental Contamination and Toxicology |date=January 2017 |volume=98 |issue=1 |pages=2–7 |doi=10.1007/s00128-016-1898-0}}</ref> Hydrophobic OPEs are more likely to be bioaccumulated and biomagnified in aquatic ecosystems.<ref name=":5" /> Halogenated organophosphates tend to be denser than water and sink, causing them to accumulate in sediments.<ref>{{Cite journal|last1=McDonough|first1=Carrie A.|last2=De Silva|first2=Amila O.|last3=Sun|first3=Caoxin|last4=Cabrerizo|first4=Ana|last5=Adelman|first5=David|last6=Soltwedel|first6=Thomas|last7=Bauerfeind|first7=Eduard|last8=Muir|first8=Derek C. G.|last9=Lohmann|first9=Rainer|date=2018-06-05|title=Dissolved Organophosphate Esters and Polybrominated Diphenyl Ethers in Remote Marine Environments: Arctic Surface Water Distributions and Net Transport through Fram Strait|url=https://pubs.acs.org/doi/10.1021/acs.est.8b01127|journal=Environmental Science & Technology|language=en|volume=52|issue=11|pages=6208–6216|doi=10.1021/acs.est.8b01127|pmid=29787253|bibcode=2018EnST...52.6208M|issn=0013-936X}}</ref>


==In nature==
==Industrial materials==
===Pesticides{{anchor|Insecticides}}===
[[File:Anatoxin-a(S)_skeletal.svg|[[Guanitoxin]] is a naturally occurring organophosphate produced by [[cyanobacteria]]|thumb]]
[[File:Malathion.png|thumb|right|[[Malathion]], one of the first organophosphate insecticides. It remains important as a Vector control agent.]]
The detection of OPEs in the air as far away as Antarctica at concentrations around 1&nbsp;ng/m<sup>3</sup> suggests their persistence in air, and their potential for long-range transport.<ref name=":7" /> OPEs were measured in high frequency in air and water and widely distributed in northern hemisphere.<ref>{{Cite journal|last1=Salamova|first1=Amina|last2=Ma|first2=Yuning|last3=Venier|first3=Marta|last4=Hites|first4=Ronald A.|date=2014-01-14|title=High Levels of Organophosphate Flame Retardants in the Great Lakes Atmosphere|url=https://doi.org/10.1021/ez400034n|journal=[[Environmental Science & Technology Letters]]|volume=1|issue=1|pages=8–14|doi=10.1021/ez400034n}}</ref><ref name=":8">{{Cite journal|last1=Venier|first1=Marta|last2=Dove|first2=Alice|last3=Romanak|first3=Kevin|last4=Backus|first4=Sean|last5=Hites|first5=Ronald|date=2014-08-19|title=Flame Retardants and Legacy Chemicals in Great Lakes' Water|url=https://pubs.acs.org/doi/10.1021/es501509r|journal=[[Environmental Science & Technology]]|language=en|volume=48|issue=16|pages=9563–9572|doi=10.1021/es501509r|pmid=25045802|bibcode=2014EnST...48.9563V|issn=0013-936X}}</ref> The chlorinated OPEs (TCEP, TCIPP, TDCIPP) in urban sampling sites and non-halogenated like TBOEP in rural areas respectively were frequently measured in the environment across multiple sites. In the Laurentian Great Lakes total OPEs concentrations were found to be 2–3 orders of magnitude higher than concentrations of brominated flame retardants measured in similar air.<ref name=":8" /> Waters from rivers in Germany, Austria, and Spain have been consistently recorded for TBOEP and TCIPP at highest concentrations.<ref name=":7" /> From these studies, it is clear that OPE concentrations in both air and water samples are often orders of magnitude higher than other flame retardants, and that concentrations are largely dependent on sampling location, with higher concentrations in more urban, polluted locations.

{{anchor|Insecticides}}
==Pesticides==
Today, organophosphates make up about 50% of the killing agents in chemical [[insecticide]]s.<ref name=":0">{{Cite journal|date=2016-11-29|title=Organophosphates: Background, Pathophysiology, Epidemiology|url=http://emedicine.medscape.com/article/1175139-overview#a4%3E/|url-status=live|archive-url=https://web.archive.org/web/20170424175202/http://emedicine.medscape.com/article/1175139-overview#a4%3E/|archive-date=2017-04-24}}</ref>{{Failed verification|date=May 2021|reason=Referenced sections for both archived and current versions of ref failed verification.}}


Organophosphates are best known for their use as pesticides. The vast majority are [[insecticides]] and are used either to protect crops, or as [[vector control]] agents to reduce the transmission of diseases spread by insects, such as mosquitoes. Health concerns have seen their use significantly decrease since the turn of the century.<ref>{{cite web |title=Status and Trends of Pesticide Use |url=https://wedocs.unep.org/20.500.11822/40351 |website=United Nations Environment Programme |publisher=World Health Organization, & Food and Agriculture Organization of the United Nations |date=2022}}</ref><ref name=Vector-trends>{{cite journal |last1=van den Berg |first1=Henk |last2=da Silva Bezerra |first2=Haroldo Sergio |last3=Al-Eryani |first3=Samira |last4=Chanda |first4=Emmanuel |last5=Nagpal |first5=Bhupender N. |last6=Knox |first6=Tessa B. |last7=Velayudhan |first7=Raman |last8=Yadav |first8=Rajpal S. |title=Recent trends in global insecticide use for disease vector control and potential implications for resistance management |journal=Scientific Reports |date=13 December 2021 |volume=11 |issue=1 |doi=10.1038/s41598-021-03367-9}}</ref> [[Glyphosate]] is sometimes called an organophosphate, but is in-fact a [[phosphonate]]. It's chemistry, mechanism of toxicity and end-use as a herbicide are different from the organophosphate insecticides.
Organophosphate pesticides (OPPs), like some [[nerve agents]], inhibit [[acetylcholinesterase]] (IRAC [[mode of action]] 1b),<ref name="IRAC-MoAs-9.4" /> which is broadly essential for normal function in insects, but also in humans and many other animals.<ref name="webmd.com">{{cite web |last= Goodman |first= Brenda |title= Pesticide Exposure in Womb Linked to Lower IQ |work= Health & Pregnancy |publisher= [[WebMD]]|date= 21 Apr 2011 |url= http://www.webmd.com/baby/news/20110421/pesticide-exposure-in-womb-linked-to-lower-iq |url-status= live |archive-url= https://web.archive.org/web/20110424105631/http://www.webmd.com/baby/news/20110421/pesticide-exposure-in-womb-linked-to-lower-iq |archive-date= 2011-04-24 }}</ref> OPPs affect this enzyme in varied ways, a principal one being through [[irreversible inhibition|irreversible covalent inhibition]],<ref>{{Cite journal | pmc=4238091| year=2014| last1=Peter| first1=J. V.| title=Clinical features of organophosphate poisoning: A review of different classification systems and approaches| journal=[[Indian Journal of Critical Care Medicine]]| volume=18| issue=11| pages=735–745| last2=Sudarsan| first2=T. I.| last3=Moran| first3=J. L.| doi=10.4103/0972-5229.144017| pmid=25425841| doi-access=free}}</ref> and so create potentials for poisoning that vary in degree. The brain sends out neurotransmitters to the nerve endings in the body; organophosphates disrupt this process from occurring. This chemical, organophosphate works by disrupting the enzyme acetylcholinesterase. Acetylcholinesterase breaks down the acetylcholine neurotransmitter, which sends out signals to other nerve endings in the body.<ref name=":0" />


The development of organophosphate insecticides dates back to the 1930s and is generally credited to [[Gerhard Schrader]].<ref name="OPs at 80">{{cite journal |last1=Costa |first1=Lucio G |title=Organophosphorus Compounds at 80: Some Old and New Issues |journal=Toxicological Sciences |date=1 March 2018 |volume=162 |issue=1 |pages=24–35 |doi=10.1093/toxsci/kfx266 |doi-access=free}}</ref> At the time pesticides were largely limited to arsenic salts ([[calcium arsenate]], [[lead arsenate]] and [[Paris green]])<ref>{{cite news|url=https://cen.acs.org/articles/87/i7/Pinpointing-Trends-Pesticide-Use.html|title=Pinpointing Trends In Pesticide Use. Limited data indicate that pesticide use has dropped since the 1970s| vauthors = Ritter SK |work=Chemical & Engineering News|publisher=[[American Chemical Society|ACS]]|year=2009|issue=7|volume=87|issn=0009-2347}}</ref> or [[pyrethrin]] plant extracts, all of which had major problems.<ref>{{cite journal |last1=Costa |first1=Lucio G. |title=Toxicology of Pesticides: A Brief History |journal=Toxicology of Pesticides |date=1987 |pages=1–10 |doi=10.1007/978-3-642-70898-5_1}}</ref> Schrader was seeking more effective agents, however while some organophosphates were found to be far more dangerous to insects than higher animals,<ref>{{cite journal |last1=Richmond |first1=Martha |title=Discovery and Commercial Introduction and Mode of Action of Parathion, Malathion, Diazinon, Tetrachlorvinphos, and Glyphosate |journal=Cancer Hazards: Parathion, Malathion, Diazinon, Tetrachlorvinphos and Glyphosate |date=2021 |pages=3–11 |doi=10.1007/978-3-030-81953-8_1}}</ref> the potential effectiveness of others as [[chemical weapon]]s did not go unnoticed. The development of organophosphate insecticides and the earliest [[nerve agent]]s was conjoined, with Schrader also developing the nerve agents [[Tabun (nerve agent)|tabun]] and [[sarin]]. Organophosphate pesticides were not commercialised until after WWII. [[Parathion]] was among the first marketed, followed by [[malathion]] and [[azinphosmethyl]] <!--very early ones may have also included [[dimefox]], [[diisopropyl fluorophosphate]], [[Schradan]] and Bladan ([[Hexaethyl tetraphosphate]]?) -->. Although organophosphates were used in considerable qualities they were originally less important than [[organochlorine]] insecticides such as [[DDT]], [[dieldrin]], and [[heptachlor]]. When many of the organochlorines were banned in the 1970s, following the publishing of [[Silent Spring]], organophosphates became the most important class of insecticides globally. Nearly 100 were commercialised, with the following being a varied selection:
For instance, [[parathion]], one of the first OPPs commercialized, is many times more potent than [[malathion]], an insecticide used in combating the [[Mediterranean fruit fly]] (Med-fly) and [[West Nile virus]]-transmitting mosquitoes.<ref>{{Cite web | url = https://www.epa.gov/pesticides#malathion | publisher = [[Environmental Protection Agency]] | title = Malathion | date = 20 August 2015 | url-status = live | archive-url = https://web.archive.org/web/20170504113220/https://www.epa.gov/pesticides#malathion | archive-date = 2017-05-04 }}</ref> Human and animal exposure to them can be through ingestion of foods containing them, or via absorption through the skin or lungs.<ref name="webmd.com" />


The human and animal toxicity of OPPs make them a societal health and environmental concern;<ref name="webmd.com"/> the EPA banned most residential uses of organophosphates in 2001, but their agricultural use, as pesticides on fruits and vegetables, is still permitted, as is their use in [[Mosquito control|mosquito abatement]] in public spaces such as parks.<ref name="webmd.com"/> For instance, the most commonly used OPP in the U.S., malathion,<ref name="pmid17720683"/> sees wide application in agriculture, residential landscaping, and pest control programs (including mosquito control in public recreation areas).<ref name=EPAmalathion/> As of 2010, forty such OPPs were registered for use in the U.S.,<ref name=MaughLAT10>{{cite news |url=http://articles.latimes.com/2010/may/16/science/la-sci-pesticides-20100517 |work=Los Angeles Times |first=Thomas H. |last=Maugh II |title=Study links pesticide to ADHD in children |date=16 May 2010 |url-status=live |archive-url=http://archive.wikiwix.com/cache/20110423054445/http://articles.latimes.com/2010/may/16/science/la-sci-pesticides-20100517 |archive-date=23 April 2011 }}</ref> with at least {{Convert|73|e6lb|abbr=off}} used in one time period{{which|date=March 2017}} in agricultural and residential settings.<ref name=MaughLAT10/> Commonly used organophosphates have included:
{{div col|colwidth=18em}}
{{div col|colwidth=18em}}
*[[Acephate]]
*[[Azinphos-methyl]]
*[[Bensulide]]
*[[Chlorethoxyfos]]
*[[Coumaphos]]
*[[Diazinon]]
*[[Dichlorvos]]
*[[Dicrotophos]]
*[[Dimethoate]]
*[[Disulfoton]]
*[[Ethion]]
*[[Ethoprop]]
*[[Ethyl parathion]]
*[[Fenamiphos]]
*[[Fenitrothion]]
*[[Fonofos]]
*[[Isoxathion]]
*[[Malathion]]
*[[Methamidophos]]
*[[Methidathion]]
*[[Mevinphos]]
*[[Naled]]
*[[Phosmet]]
*[[Profenofos]]
*[[Propetamphos]]
*[[Sulfotep]]
*[[Tebupirimfos]]
*[[Temephos]]
*[[Terbufos]]
*[[Tetrachlorvinphos]]
*[[Triazofos]]
*[[Trichlorfon]]
{{div col end}}


Organophosphate insecticides are [[acetylcholinesterase inhibitor]]s, and when introduced to an organism they act to fatally disrupt the transmission of nerve signals. The risk of human death through [[organophosphate poisoning]]<ref>{{Cite journal | pmc=4238091| year=2014| last1=Peter| first1=J. V.| title=Clinical features of organophosphate poisoning: A review of different classification systems and approaches| journal=Indian Journal of Critical Care Medicine| volume=18| issue=11| pages=735–745| last2=Sudarsan| first2=T. I.| last3=Moran| first3=J. L.| doi=10.4103/0972-5229.144017| pmid=25425841}}</ref> was obvious from the start and let to efforts to lower toxicity again mammals while not reducing efficacy again insects.<ref>{{cite journal |last1=O’Brien |first1=R. D. |last2=Thorn |first2=G. D. |last3=Fisher |first3=R. W. |title=New Organophosphate Insecticides Developed on Rational Principles1 |journal=Journal of Economic Entomology |date=1 October 1958 |volume=51 |issue=5 |pages=714–718 |doi=10.1093/jee/51.5.714}}</ref><ref>{{cite journal |last1=Salgado |first1=Vincent L |last2=David |first2=Michael D |title=Chance and design in proinsecticide discovery |journal=Pest Management Science |date=April 2017 |volume=73 |issue=4 |pages=723–730 |doi=10.1002/ps.4502}}</ref>
* [[parathion]]
* [[malathion]]<ref name=EPAmalathion>{{cite web|url=http://www.epa.gov/opp00001/health/mosquitoes/malathion4mosquitoes.htm|title=Malathion for Mosquito Control - Pesticides - US EPA|date=7 March 2011|access-date=29 April 2018|url-status=bot: unknown|archive-url=https://web.archive.org/web/20110307234024/http://www.epa.gov/opp00001/health/mosquitoes/malathion4mosquitoes.htm|archive-date=7 March 2011}}</ref><ref name="pmid17720683">{{cite journal |author=Bonner MR |title=Malathion Exposure and the Incidence of Cancer in the Agricultural Health Study |journal=[[American Journal of Epidemiology]]|volume= 166 |issue= 9|pages=1023–34|year=2007 |pmid=17720683 |doi=10.1093/aje/kwm182 |name-list-style=vanc|author2=Coble J |author3=Blair A |display-authors=3 |last4=Beane Freeman |first4=L. E. |last5=Hoppin |first5=J. A. |last6=Sandler |first6=D. P. |last7=Alavanja |first7=M. C. R.|doi-access=free }}</ref>
* [[methyl parathion]]
* [[chlorpyrifos]]
* [[diazinon]]
* [[dichlorvos]]
* [[phosmet]]
* [[fenitrothion]]<ref>{{cite web |title= Fenitrothion |work= Pesticide Information Profiles |publisher= Extension Toxicology Network |date= Sep 1995 |url= http://extoxnet.orst.edu/pips/fenitrot.htm |url-status= live |archive-url= https://web.archive.org/web/20040821163731/http://extoxnet.orst.edu/pips/fenitrot.htm |archive-date= 2004-08-21 }}</ref>
* [[tetrachlorvinphos]]
* [[azamethiphos]]
* [[azinphos-methyl]]
* [[terbufos]]{{div col end}}


The majority of organophosphate insecticides are [[organothiophosphate]]s (P=S) or [[phosphorodiamidate]]s (P-N), both of which are significantly weaker acetylcholinesterase inhibitors than the corresponding phosphates (P=O). They are 'activated' biologically by the exposed organism, via oxidative conversion of P=S to P=O,<ref>{{cite journal |last1=Gage |first1=J. C. |title=A cholinesterase inhibitor derived from OO -diethyl O - p -nitrophenyl thiophosphate in vivo |journal=Biochemical Journal |date=1 June 1953 |volume=54 |issue=3 |pages=426–430 |doi=10.1042/bj0540426}}</ref> hydroxylation,<ref>{{cite journal |title=The decomposition of some organophosphorus insecticides and related compounds in plants |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |date=22 December 1955 |volume=239 |issue=663 |pages=191–214 |doi=10.1098/rstb.1955.0009}}</ref><ref>{{cite journal |last1=Spencer |first1=E. Y. |last2=O'Brien |first2=R. D. |last3=White |first3=R. W. |title=Metabolism of Insecticides, Permanganate Oxidation Products of Schradan |journal=Journal of Agricultural and Food Chemistry |date=February 1957 |volume=5 |issue=2 |pages=123–127 |doi=10.1021/jf60072a004}}</ref>, or other related process which see them transformed into organophosphates. In mammals these transformations occur almost exclusively in the liver,<ref>{{cite journal |last1=Davison |first1=A. N. |title=Return of cholinesterase activity in the rat after inhibition by organophosphorus compounds. 2. A comparative study of true and pseudo cholinesterase |journal=Biochemical Journal |date=1 June 1955 |volume=60 |issue=2 |pages=339–346 |doi=10.1042/bj0600339}}</ref> while in insects they take place in the gut and [[fat body]].<ref>{{cite journal |last1=Metcalf |first1=Robert L. |last2=March |first2=Ralph B. |title=Further Studies1 on the Mode of Action of Organic Thionophosphate Insecticides |journal=Annals of the Entomological Society of America |date=1 March 1953 |volume=46 |issue=1 |pages=63–74 |doi=10.1093/aesa/46.1.63}}</ref><ref>{{cite journal |last1=Spencer |first1=E. Y. |last2=O'Brien |first2=R. D. |title=Schradan, Enhancement of Anticholinesterase Activity in Octamethylpyrophosphoramide by Chlorine |journal=Journal of Agricultural and Food Chemistry |date=August 1953 |volume=1 |issue=11 |pages=716–720 |doi=10.1021/jf60011a003}}</ref><ref>{{cite journal |last1=O'Brien |first1=R. D. |title=The effect of SKF 525A (2-diethylaminoethyl 2:2-diphenylvalerate hydrochloride) on organophosphate metabolism in insects and mammals |journal=Biochemical Journal |date=1 May 1961 |volume=79 |issue=2 |pages=229–235 |doi=10.1042/bj0790229}}</ref> As the transformations are handled by different [[enzyme]]s in different classes of organism it is possible to find compounds which activate more rapidly and completely in insects, and thus display more targeted lethal action.
Studies have shown that prolonged exposure to OPPs—e.g., in the case of farm workers—can lead to health problems, including increased risks for cardiovascular and respiratory disease, and cancer. In the case of pregnant women, exposure can result in premature births.<ref>{{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]]|date=May 2011|volume=30|issue=5|pages=879–87|doi=10.1377/hlthaff.2011.0153|pmid=21555471|url=https://escholarship.org/content/qt1kq0196d/qt1kq0196d.pdf?t=onzqj2}}</ref> In addition, permanent damage to the brain's chemical make-up, and changes in human behavior and emotion can occur to the fetus in pregnant women.<ref>{{Cite web|url=https://tools.niehs.nih.gov/srp/research/research4_s3_s5.cfm|title=Organophosphates|website=tools.niehs.nih.gov|access-date=2017-04-24|url-status=live|archive-url=https://web.archive.org/web/20170424180321/https://tools.niehs.nih.gov/srp/research/research4_s3_s5.cfm|archive-date=2017-04-24}}</ref>


This selectivity is far from perfect and organophosphate insecticides remain acutely toxic to humans, with many thousands estimated to be killed each year due to intentional<ref>{{cite journal |last1=Mew |first1=Emma J. |last2=Padmanathan |first2=Prianka |last3=Konradsen |first3=Flemming |last4=Eddleston |first4=Michael |last5=Chang |first5=Shu-Sen |last6=Phillips |first6=Michael R. |last7=Gunnell |first7=David |title=The global burden of fatal self-poisoning with pesticides 2006-15: Systematic review |journal=Journal of Affective Disorders |date=September 2017 |volume=219 |pages=93–104 |doi=10.1016/j.jad.2017.05.002}}</ref> or unintentional poisoning. Beyond their [[acute toxicity]], exposure to organophosphates is associated with a number of heath risks, including [[organophosphate-induced delayed neuropathy]] (muscle weakness) and developmental neurotoxicity.<ref name="OPs at 80" /><ref>{{cite journal |last1=Jokanović |first1=Milan |last2=Oleksak |first2=Patrik |last3=Kuca |first3=Kamil |title=Multiple neurological effects associated with exposure to organophosphorus pesticides in man |journal=Toxicology |date=January 2023 |volume=484 |pages=153407 |doi=10.1016/j.tox.2022.153407}}</ref><ref>{{cite web |title=The environmental, human health and economic impacts of pesticides |url=https://wedocs.unep.org/bitstream/handle/20.500.11822/40354/Pesticides_Ch5.pdf |publisher=United Nations Environment Programme [UNEP] |access-date=2 January 2024}}</ref> There is limited evidence that certain compounds cause cancer, including [[malathion]] and [[diazinon]].<ref>{{Cite journal |date=2017 |title=Some Organophosphate Insecticides and Herbicides |journal=IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. |publisher=[[International Agency for Research on Cancer]] |volume=12 |page=464 |pmid=31829533}}</ref> Children<ref>{{cite journal |last1=Muñoz-Quezada |first1=María Teresa |last2=Lucero |first2=Boris A. |last3=Barr |first3=Dana B. |last4=Steenland |first4=Kyle |last5=Levy |first5=Karen |last6=Ryan |first6=P. Barry |last7=Iglesias |first7=Veronica |last8=Alvarado |first8=Sergio |last9=Concha |first9=Carlos |last10=Rojas |first10=Evelyn |last11=Vega |first11=Catalina |title=Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: A systematic review |journal=NeuroToxicology |date=December 2013 |volume=39 |pages=158–168 |doi=10.1016/j.neuro.2013.09.003}}</ref> and farmworkers<ref>{{cite journal |last1=Muñoz-Quezada |first1=María Teresa |last2=Lucero |first2=Boris Andrés |last3=Iglesias |first3=Verónica Paz |last4=Muñoz |first4=María Pía |last5=Cornejo |first5=Claudia Alejandra |last6=Achu |first6=Eduardo |last7=Baumert |first7=Brittney |last8=Hanchey |first8=Arianna |last9=Concha |first9=Carlos |last10=Brito |first10=Ana María |last11=Villalobos |first11=Marcos |title=Chronic exposure to organophosphate (OP) pesticides and neuropsychological functioning in farm workers: a review |journal=International Journal of Occupational and Environmental Health |date=2 January 2016 |volume=22 |issue=1 |pages=68–79 |doi=10.1080/10773525.2015.1123848}}</ref> are considered to be at greater risk.
Organophosphate pesticides degrade rapidly by hydrolysis on exposure to sunlight, air, and soil, although small amounts can be detected in food and drinking water.{{citation needed|date=March 2017}} Organophosphates contaminate drinking water by moving through the soil to the ground water.<ref name="auto">{{Cite web|url=https://www.cdc.gov/nceh/clusters/fallon/organophosfaq.htm|title=Fallon Nevada: FAQs: Organophosphates|access-date=2018-03-11|publisher=[[Centers for Disease Control and Prevention]], Department of Health and Human Services|url-status=live|archive-url=https://web.archive.org/web/20180312204746/https://www.cdc.gov/nceh/clusters/fallon/organophosfaq.htm|archive-date=2018-03-12}}</ref> When the pesticide degrades, it is broken down into several chemicals.<ref name="auto"/> Organophosphates degrade faster than the organochlorides.{{citation needed|date=March 2017}} The greater acute toxicity of OPPs results in the elevated risk associated with this class of compounds (see the Toxicity section below).


[[Pesticide regulation in the United States]] and the [[regulation of pesticides in the European Union]] have both been increasing restrictions on organophosphate pesticides since the 1990s, particularly when used for crop protection. The use of organophosphates has decreased considerably since that time, having been replaced by [[pyrethroid]]s and [[neonicotinoid]]s, which are effective a much lower levels.<ref>{{cite web |title=Status and Trends of Pesticide Use |url=https://wedocs.unep.org/20.500.11822/40351 |website=United Nations Environment Programme |publisher=World Health Organization, & Food and Agriculture Organization of the United Nations |date=2022}}</ref> Reported cases of organophosphate poisoning in the US have reduced during this period.<ref>{{cite journal |last1=Clune |first1=Alison L. |last2=Ryan |first2=P. Barry |last3=Barr |first3=Dana Boyd |title=Have Regulatory Efforts to Reduce Organophosphorus Insecticide Exposures Been Effective? |journal=Environmental Health Perspectives |date=April 2012 |volume=120 |issue=4 |pages=521–525 |doi=10.1289/ehp.1104323}}</ref><ref>{{cite journal |last1=Stone |first1=David L |last2=Sudakin |first2=Daniel L |last3=Jenkins |first3=Jeffrey J |title=Longitudinal trends in organophosphate incidents reported to the National Pesticide Information Center, 1995–2007 |journal=Environmental Health |date=December 2009 |volume=8 |issue=1 |doi=10.1186/1476-069X-8-18}}</ref> Regulation in the global south can be less extensive.<ref>{{cite journal |last1=Souza |first1=Marília Cristina Oliveira |last2=Cruz |first2=Jonas Carneiro |last3=Cesila |first3=Cibele Aparecida |last4=Gonzalez |first4=Neus |last5=Rocha |first5=Bruno Alves |last6=Adeyemi |first6=Joseph A. |last7=Nadal |first7=Marti |last8=Domingo |first8=José L. |last9=Barbosa |first9=Fernando |title=Recent trends in pesticides in crops: A critical review of the duality of risks-benefits and the Brazilian legislation issue |journal=Environmental Research |date=July 2023 |volume=228 |pages=115811 |doi=10.1016/j.envres.2023.115811}}</ref><ref>{{cite journal |last1=Galt |first1=Ryan E. |title=Beyond the circle of poison: Significant shifts in the global pesticide complex, 1976–2008 |journal=Global Environmental Change |date=October 2008 |volume=18 |issue=4 |pages=786–799 |doi=10.1016/j.gloenvcha.2008.07.003 |url=https://escholarship.org/content/qt1d88g9fw/qt1d88g9fw.pdf}}</ref>
===Resistance===
Arthropod mechanisms of [[insecticide resistance|resistance]] are well studied and well characterized.<ref name="Investigating" /> [[Polymerase chain reaction]] (PCR) [[assay]]s are available for [[molecular diagnosis]] of resistant [[genotype]]s, including that of Carvalho ''et al.'', 2013.<ref name="Investigating">
:{{cite journal|issue=1–2|year=2014|publisher=[[Elsevier BV]]|pages=6–20|first5=Zafar|first4=John|first3=Douglas|first2=Arfan|first1=Rao|last5=Iqbal|last4=Gilleard|last3=Colwell|last2=Zaman|last1=Abbas|journal=[[Veterinary Parasitology]]|issn=0304-4017|volume=203|s2cid=205636621|pmid=24709006|doi=10.1016/j.vetpar.2014.03.006|title=Acaricide resistance in cattle ticks and approaches to its management: The state of play}}
:
:{{cite journal|year=2016|publisher=[[Elsevier BV]]|volume=15|last1=Blanco|first1=C|pages=131–138|last2=Chiaravalle|first2=W|last3=Rizza|first3=M|last4=Farias|first4=J|last5=Garcia|first5=M|last6=Gastaminza|first6=G|last7=Sanchez|first7=D|last8=Murua|first8=M|last9=Omoto|first9=C|last10=Pieralisi|first10=B|last11=Rodriguez|first11=J|last12=Rodriguez|first12=J|last13=Teran|first13=H|last14=Vargas|first14=A|last15=Valencia|first15=S|last16=Willink|first16=E|journal=[[Current Opinion in Insect Science]]|issn=2214-5745|s2cid=24543393|pmid=27436743|doi=10.1016/j.cois.2016.04.012|title=Current situation of pests targeted by Bt crops in Latin America}}
:
:These reviews cite this research.
:
:{{cite journal|year=2013|issue=4|publisher=[[Public Library of Science]] (PLoS)|journal=[[PLoS ONE]]|issn=1932-6203|volume=8|first5=Chris|first4=Martin|first3=Linda|first2=Celso|first1=Renato|last5=Bass|last4=Williamson|last3=Field|last2=Omoto|last1=Carvalho|s2cid=12597068|doi=10.1371/journal.pone.0062268|title=Investigating the Molecular Mechanisms of Organophosphate and Pyrethroid Resistance in the Fall Armyworm ''Spodoptera frugiperda''|page=e62268|pmid=23614047|pmc=3629120|doi-access=free}}
</ref>


In 2015, only 3 of the 50 most common crop-specific pesticides used in the US were organophosphates ([[Chlorpyrifos]], [[Bensulide]], [[Acephate]]),<ref>{{cite journal |last1=Maggi |first1=Federico |last2=Tang |first2=Fiona H. M. |last3=la Cecilia |first3=Daniele |last4=McBratney |first4=Alexander |title=PEST-CHEMGRIDS, global gridded maps of the top 20 crop-specific pesticide application rates from 2015 to 2025 |journal=Scientific Data |date=12 September 2019 |volume=6 |issue=1 |doi=10.1038/s41597-019-0169-4}}</ref> of these [[Chlorpyrifos]] was banned in 2021.<ref>{{cite web |title=Tolerance Revocations: Chlorpyrifos |url=https://www.regulations.gov/document/EPA-HQ-OPP-2021-0523-0001 |website=www.regulations.gov |access-date=2 January 2024 |quote=Federal Register Number: 2021-18091}}</ref> No new organophosphate pesticides have been commercialised in the 21st century.<ref>{{cite journal |last1=Umetsu |first1=Noriharu |last2=Shirai |first2=Yuichi |title=Development of novel pesticides in the 21st century |journal=Journal of Pesticide Science |date=20 May 2020 |volume=45 |issue=2 |pages=54–74 |doi=10.1584/jpestics.D20-201}}</ref> The situation in [[vector control]] is fairly similar, despite different risk trade-offs,<ref>{{cite journal |last1=Gray |first1=George M. |last2=Hammitt |first2=James K. |title=Risk/Risk Trade‐offs in Pesticide Regulation: An Exploratory Analysis of the Public Health Effects of a Ban on Organophosphate and Carbamate Pesticides |journal=Risk Analysis |date=October 2000 |volume=20 |issue=5 |pages=665–680 |doi=10.1111/0272-4332.205060}}</ref> with the global use of organophosphate insecticides falling by nearly half between 2010 and 2019.<ref name=Vector-trends /> [[Pirimiphos-methyl]], [[Malathion]] and [[Temefos]] are still important, primarily for the control of [[malaria]] in the Asia-Pacific region.<ref name=Vector-trends/> The continued use of these agents is being challenged by the emergence of [[insecticide resistance]].<ref>{{cite journal |last1=Siegfried |first1=Blair D. |last2=Scharf |first2=Michael E. |title=Mechanisms of Organophosphate Resistance in Insects |journal=Biochemical Sites of Insecticide Action and Resistance |date=2001 |pages=269–291 |doi=10.1007/978-3-642-59549-3_13}}</ref>
==Nerve agents==
{{main|Nerve agents}}


===History===
=== Flame retardants ===
{{main|flame retardants}}
Early pioneers in the field include [[Jean Louis Lassaigne]] (early 19th century) and [[Philippe de Clermont]] (1854). In 1932, German chemist Willy Lange and his graduate student, Gerde von Krueger, first described the [[cholinergic]] nervous system effects of organophosphates, noting a choking sensation and a dimming of vision after exposure on themselves, which they attributed to the esters themselves.<ref>Petroianu, G.A. 2010. Toxicity of phosphor esters: Willy Lange (1900–1976) and Gerda von
Krueger (1907–after 1970). ''College of Medicine, Florida International University, Miami, USA.'' Retrieved from: {{cite web |url=http://www.ingentaconnect.com/contentone/govi/pharmaz/2010/00000065/00000010/art00013?crawler=true |title=Archived copy |access-date=2018-03-12 |url-status=live |archive-url=https://web.archive.org/web/20180313092938/http://www.ingentaconnect.com/contentone/govi/pharmaz/2010/00000065/00000010/art00013?crawler=true |archive-date=2018-03-13 }} .</ref> This discovery later inspired German chemist [[Gerhard Schrader]] at company [[IG Farben]] in the 1930s to experiment with these compounds as insecticides. Their potential use as chemical warfare agents soon became apparent, and the Nazi government put Schrader in charge of developing organophosphate (in the broader sense of the word) nerve gases. Schrader's laboratory discovered the G series of weapons, which included [[Sarin]], [[Tabun (nerve agent)|Tabun]], and [[Soman]]. The Nazis produced large quantities of these compounds, though did not use them during World War II. British scientists experimented with a [[cholinergic]] organophosphate of their own, called [[diisopropylfluorophosphate]], during the war. The British later produced [[VX (nerve agent)|VX]] nerve agent, which was many times more potent than the G series, in the early 1950s, almost 20 years after the Germans had discovered the G series.


Flame retardants are added to materials to prevent combustion and to delay the spread of fire after ignition. Organophosphate flame retardants are part of a wider family of phosphorous-based agents which include organic [[phosphonate]] and [[phosphinate]] esters, in addition to inorganic salts.<ref name="retardants-review">{{cite journal |last1=van der Veen |first1=Ike |last2=de Boer |first2=Jacob |title=Phosphorus flame retardants: Properties, production, environmental occurrence, toxicity and analysis |journal=Chemosphere |date=August 2012 |volume=88 |issue=10 |pages=1119–1153 |doi=10.1016/j.chemosphere.2012.03.067}}</ref><ref name="Clariant">{{cite journal |last1=Schmitt |first1=Elmar |title=Phosphorus-based flame retardants for thermoplastics |journal=Plastics, Additives and Compounding |date=May 2007 |volume=9 |issue=3 |pages=26–30 |doi=10.1016/S1464-391X(07)70067-3}}</ref> When some prominent [[brominated flame retardant]] were banned in the early 2000s phosphorous-based agents were promoted as safer replacements. This has led to a large increase in their use, with an estimated 1 million tonnes of organophosphate flame retardants produced in 2018.<ref>{{cite journal |last1=He |first1=Huan |last2=Gao |first2=Zhanqi |last3=Zhu |first3=Donglin |last4=Guo |first4=Jiehong |last5=Yang |first5=Shaogui |last6=Li |first6=Shiyin |last7=Zhang |first7=Limin |last8=Sun |first8=Cheng |title=Assessing bioaccessibility and bioavailability of chlorinated organophosphorus flame retardants in sediments |journal=Chemosphere |date=December 2017 |volume=189 |pages=239–246 |doi=10.1016/j.chemosphere.2017.09.017}}</ref> Safety concerns have subsequently been raised about some of these reagents,<ref>{{cite journal |last1=Blum |first1=Arlene |last2=Behl |first2=Mamta |last3=Birnbaum |first3=Linda S. |last4=Diamond |first4=Miriam L. |last5=Phillips |first5=Allison |last6=Singla |first6=Veena |last7=Sipes |first7=Nisha S. |last8=Stapleton |first8=Heather M. |last9=Venier |first9=Marta |title=Organophosphate Ester Flame Retardants: Are They a Regrettable Substitution for Polybrominated Diphenyl Ethers? |journal=Environmental Science & Technology Letters |date=12 November 2019 |volume=6 |issue=11 |pages=638–649 |doi=10.1021/acs.estlett.9b00582|doi-access=free}}</ref><ref>{{cite journal |last1=Du |first1=Jia |last2=Li |first2=Huanxuan |last3=Xu |first3=Shaodan |last4=Zhou |first4=Qingwei |last5=Jin |first5=Meiqing |last6=Tang |first6=Junhong |title=A review of organophosphorus flame retardants (OPFRs): occurrence, bioaccumulation, toxicity, and organism exposure |journal=Environmental Science and Pollution Research |date=August 2019 |volume=26 |issue=22 |pages=22126–22136 |doi=10.1007/s11356-019-05669-y}}</ref> with several under regulatory scrutiny.<ref>{{cite web |title=ECHA identifies certain brominated flame retardants as candidates for restriction |url=https://echa.europa.eu/-/echa-identifies-certain-brominated-flame-retardants-as-candidates-for-restriction |website=echa.europa.eu |publisher=European Chemicals Agency |access-date=3 January 2024}}</ref><ref name=ECHA-PFR>{{cite web |title=Regulatory strategy for flame retardant |url=https://echa.europa.eu/documents/10162/2082415/flame_retardants_strategy_en.pdf/ |publisher=European Chemicals Agency |access-date=3 January 2024}}{{DOI|10.2823/854233}}</ref>
After World War II, American companies gained access to some information from Schrader's laboratory, and began synthesizing organophosphate pesticides in large quantities. [[Parathion]] was among the first marketed, followed by [[malathion]] and azinphosmethyl. The popularity of these insecticides increased after many of the [[organochlorine]] insecticides, such as [[DDT]], [[dieldrin]], and [[heptachlor]], were banned in the 1970s.


Organophosphate flame retardants were first developed in the first half of the twentieth century in the from of [[triphenyl phosphate]], [[tricresyl phosphate]] and [[tributyl phosphate]] for use in plastics like [[cellulose nitrate]] and [[cellulose acetate]].<ref>{{Cite journal |last=Weil |first=E.D. |last2=Levchik |first2=S.V. |date=26 January 2001 |title=Phosphorus Flame Retardants |journal=Kirk-Othmer Encyclopedia of Chemical Technology |doi=10.1002/0471238961.1608151923050912.a01.pub3}}</ref> Use in cellulose products is still significant, but the largest area of application is now in plasticized vinyl polymers, principally [[PVC]]. The more modern organophosphate flame retardants come in 2 major types; [[chlorinated]] aliphatic compounds or aromatic diphosphates.<ref name="retardants-review" /> The chlorinated compounds [[Tris(1,3-dichloro-2-propyl)phosphate|TDCPP]], [[Tris(1-chloro-2-propyl)phosphate|TCPP]] and [[Tris(2-chloroethyl) phosphate|TCEP]] are all involatile liquids, of which TCPP is perhaps the most important. They are used in [[polyurethane]] (soft furnishings), [[PVC]] (wire and cable) [[phenolic resin]]s and [[epoxy resins]]s (varnishes, coatings and adhesives). The most important of the diphosphates is [[bisphenol-A bis(diphenyl phosphate)]], with related analogues based around [[resorcinol]] and [[hydroquinone]]. These are used in [[polymer blend]]s of [[engineering plastic]]s, such as [[Poly(phenylene oxide)|PPO]]/[[High Impact Polystyrene|HIPS]] and [[Polycarbonate|PC]]/[[Acrylonitrile butadiene styrene|ABS]],<ref>{{cite journal |last1=Pawlowski |first1=Kristin H |last2=Schartel |first2=Bernhard |title=Flame retardancy mechanisms of triphenyl phosphate, resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate) in polycarbonate/acrylonitrile–butadiene–styrene blends |journal=Polymer International |date=November 2007 |volume=56 |issue=11 |pages=1404–1414 |doi=10.1002/pi.2290}}</ref> which are commonly used to make casing for electrical items like TVs, computers and home appliances.
===Structural features===
Effective organophosphates have the following structural features:


Organophosphates act multifunctionally to retard fire in both the gas phase and condensed (solid) phase. Halogenated organophosphates are more active overall as their degradation products interfere with combustion directly in the gas phase. All organophosphates have activity in the condensed phase, by forming phosphorus acids which promote [[Charring|char]] formation, insulating the surface from heat and air.
* A terminal [[oxygen]] connected to phosphorus by a double bond, i.e. a phosphoryl group
* Two lipophilic groups bonded to the phosphorus
* A [[leaving group]] bonded to the phosphorus, often a [[halide]]


Organophosphates were originally thought to be a safe replacements for brominated flame retardants, however many are now coming under regulatory pressure due to their apparent health risks.<ref name=ECHA-PFR /><ref>{{cite journal |last1=Blum |first1=Arlene |last2=Behl |first2=Mamta |last3=Birnbaum |first3=Linda S. |last4=Diamond |first4=Miriam L. |last5=Phillips |first5=Allison |last6=Singla |first6=Veena |last7=Sipes |first7=Nisha S. |last8=Stapleton |first8=Heather M. |last9=Venier |first9=Marta |title=Organophosphate Ester Flame Retardants: Are They a Regrettable Substitution for Polybrominated Diphenyl Ethers? |journal=Environmental Science & Technology Letters |date=12 November 2019 |volume=6 |issue=11 |pages=638–649 |doi=10.1021/acs.estlett.9b00582|doi-access=free}}</ref><ref>{{cite journal |last1=Du |first1=Jia |last2=Li |first2=Huanxuan |last3=Xu |first3=Shaodan |last4=Zhou |first4=Qingwei |last5=Jin |first5=Meiqing |last6=Tang |first6=Junhong |title=A review of organophosphorus flame retardants (OPFRs): occurrence, bioaccumulation, toxicity, and organism exposure |journal=Environmental Science and Pollution Research |date=August 2019 |volume=26 |issue=22 |pages=22126–22136 |doi=10.1007/s11356-019-05669-y}}</ref> The chlorinated organophosphates may be carcinogenic, while others such as [[tricresyl phosphate]] have necrotoxic properties.<ref>{{cite journal |last1=Barth |first1=Mary L. |last2=Craig |first2=Peter H. |title=Evaluation of the hazards of industrial exposure to tricresyl phosphate:a review and interpretation of the literature |journal=Journal of Toxicology and Environmental Health, Part B |date=October 1999 |volume=2 |issue=4 |pages=281–300 |doi=10.1080/109374099281142}}</ref>
====Fine tuning====
Bisphenol-A bis(diphenyl phosphate) can hydrolyse to form [[Bisphenol-A]] which is under significant scrutiny as potential [[endocrine-disrupting chemical]]. Although their names imply that they are single discreet species the some compounds are produced as complex mixtures, for instance commercial grade TCPP can contain 7 different isomers,<ref>{{cite journal |last1=Truong |first1=Jimmy W. |last2=Diamond |first2=Miriam L. |last3=Helm |first3=Paul A. |last4=Jantunen |first4=Liisa M. |title=Isomers of tris(chloropropyl) phosphate (TCPP) in technical mixtures and environmental samples |journal=Analytical and Bioanalytical Chemistry |date=December 2017 |volume=409 |issue=30 |pages=6989–6997 |doi=10.1007/s00216-017-0572-7}}</ref> while [[tricresyl phosphate]] can contain up to 10.<ref>{{cite journal |last1=Amiri |first1=Roshanak |last2=Bissram |first2=Meera J. |last3=Hashemihedeshi |first3=Mahin |last4=Dorman |first4=Frank L. |last5=Megson |first5=David |last6=Jobst |first6=Karl J. |title=Differentiating Toxic and Nontoxic Tricresyl Phosphate Isomers Using Ion–Molecule Reactions with Oxygen |journal=Journal of the American Society for Mass Spectrometry |date=5 April 2023 |volume=34 |issue=4 |pages=640–648 |doi=10.1021/jasms.2c00334}}</ref> This makes their safety profiles harder to ascertain, as material from different producers can have different compositions.<ref>{{cite journal |last1=Duarte |first1=Daniel J. |last2=Rutten |first2=Joost M.M. |last3=van den Berg |first3=Martin |last4=Westerink |first4=Remco H.S. |title=In vitro neurotoxic hazard characterization of different tricresyl phosphate (TCP) isomers and mixtures |journal=NeuroToxicology |date=March 2017 |volume=59 |pages=222–230 |doi=10.1016/j.neuro.2016.02.001}}</ref>
Within these requirements, a large number of lipophilic and leaving groups have been used. The variation of these groups is one means of fine tuning the toxicity of the compound. A good example of this chemistry are the ''P''-[[thiocyanate]] compounds which use an [[aryl]] (or [[alkyl]]) group and an alkylamino group as the lipophilic groups. The thiocyanate is the leaving group.


===Plasticisers===
== Flame retardants ==
{{main|Plasticizer}}
Flame retardants (FRs) are chemicals that have been used on diverse consumer materials to prevent combustion and to delay the spread of fire after ignition.<ref>{{Cite journal|last=Kemmlein|first=S|date=September 2003|title=BFR—governmental testing programme|url=http://dx.doi.org/10.1016/s0160-4120(03)00112-0|journal=Environment International|volume=29|issue=6|pages=781–792|doi=10.1016/s0160-4120(03)00112-0|pmid=12850096|issn=0160-4120}}</ref> The increased demand to satisfy fire safety standards for flammability of plastic materials used in devices and appliances along with the strict regulation of brominated flame retardants has driven the high volume of production and consumption of OPEs.<ref name=":4" /><ref name=":7" /> Most flame retardants used are halogenated OPEs, and the effectiveness of the flame retardant increases with the increased number of halogenated substituents.<ref name=":4" /><ref name=":7" />
Plasticisers are added to polymers and plastics to improve their flexibility and processability, giving a softer more easily deformable material. In this way brittle polymers can be made more durable. Organophosphates find use because they are multifunctional; primarily plasticising but also imparting flame resistance. The most frequently plasticised polymers are the vinyls (PVC, [[Polyvinyl butyral|PVB]], [[poly(vinyl acetate)|PVA]] and [[Polyvinyl chloride acetate|PVCA]]), as well as cellulose plastics ([[cellulose acetate]], [[nitrocellulose]] and [[cellulose acetate butyrate]]).<ref name=Ullmann's>{{cite journal | vauthors = Cadogan DF, Howick CJ |title=Plasticizers |journal=Ullmann's Encyclopedia of Industrial Chemistry |date=15 June 2000 |volume=27 |pages=613–614 |doi=10.1002/14356007.a20_439|isbn=3527306730 }}</ref> PVC dominates the market, consuming 80-90% of global plasticiser production.<ref name=Ullmann's /><ref name=Plast-market>{{cite journal |last1=Rahman |first1=M |last2=Brazel |first2=C |title=The plasticizer market: an assessment of traditional plasticizers and research trends to meet new challenges |journal=Progress in Polymer Science |date=December 2004 |volume=29 |issue=12 |pages=1223–1248 |doi=10.1016/j.progpolymsci.2004.10.001}}</ref> PVC can accept large amounts of plasticiser; a PVC item may be 70-80% plasticiser by mass in extreme cases, but loadings of between 0-50% are more common.<ref name="additives handbook">{{cite book | vauthors = Krauskopf LG |title=Plastics additives handbook |date=2009 |publisher=Carl Hanser Verlag |location=Munich |isbn=978-3-446-40801-2 |pages=485–511 |edition=6. |chapter=3.13 Plasticizers}}</ref> The main applications of these products are in wire and cable insulation, flexible pipe, automotive interiors, plastic sheeting, [[vinyl flooring]], and toys.


Pure PVC is more than 60% chlorine by mass and difficult to burn, but its flammability increases the more it is plasticised.<ref>{{cite journal |last1=William Coaker |first1=A. |title=Fire and flame retardants for PVC |journal=Journal of Vinyl and Additive Technology |date=September 2003 |volume=9 |issue=3 |pages=108–115 |doi=10.1002/vnl.10072}}</ref> Organophosphates can act as both plasticisers and flame retarders. Compounds used are typically triaryl or alkyl diaryl phosphates, with [[cresyl diphenyl phosphate]] and [[2-ethylhexyl diphenyl phosphate]] being important respective examples type.<ref>{{cite book | last=Grossman | first=Richard F | title=Handbook of Vinyl Formulating | publisher=John Wiley & Sons | page=289 | date=2008-05-02 | isbn=978-0-470-25354-0}}</ref> These are both liquids with high boiling points. Organophosphates are more expensive than traditional plasticisers and so tend used in combination with other plasticisers and flame retardants.<ref>{{cite journal |last1=Levchik |first1=Sergei V. |last2=Weil |first2=Edward D. |title=Overview of the recent literature on flame retardancy and smoke suppression in PVC |journal=Polymers for Advanced Technologies |date=October 2005 |volume=16 |issue=10 |pages=707–716 |doi=10.1002/pat.645}}</ref>
OPEs are utilized as additive flame retardants which means the concentration of these flame retardants decreases with time as they readily leak into the environment.<ref name=":7" /> There are several mechanisms flame retardants use to prevent fire, however the most effective ones are the gas phase and the solid phase reactions.<ref name=":4" /> In the solid phase, halogenated flame retardants produce a char layer on burning materials suffocating the combustion, as well as in the gas phase they remove H<sup>+</sup> and OH<sup>−</sup> radicals from the flammable gasses, by reaction with the Br and Cl atoms to further slow down the burning process.<ref name=":7" /> Non-halogenated OPEs are effective mainly in the solid phase of burning materials. Upon exposure to heat the phosphorus compounds react to form a polymeric form of phosphorous acid. The acid causes a char layer that covers the burning material, blocking it from contact with oxygen, which in turn slows down the combustion reaction.<ref name=":4" />


===Hydraulic fluids and lubricant additives===
==Health effects==
Similar to their use as plastisiers, organophosphates are well suited to use as [[hydraulic fluid]]s due to their low freezing points and high boiling points, fire-resistance, non-corrosiveness, excellent boundary lubrication properties and good general chemical stability. The triaryl phosphates are the most important group, with tricresyl phosphate being the first to be commercialised in the 1940s, with [[trixylyl phosphate]] following shortly after. Butylphenyl diphenyl phosphate and propylphenyl diphenyl phosphate became available after 1960.<ref>{{Cite book |last=Rudnick |first=L.R. |url=https://books.google.co.uk/books?id=9YXRBQAAQBAJ&pg=PA81 |title=Synthetics, Mineral Oils, and Bio-Based Lubricants: Chemistry and Technology, Second Edition |publisher=CRC Press |year=2013 |isbn=978-1-4398-5538-6 |series=Chemical Industries |pages=81-104 |chapter=Chapter 4: Neutral Phosphate Esters |doi=10.1201/9781315158150-4 |access-date=2024-01-07}}</ref>
===Poisoning===
{{Main|Organophosphate poisoning}}
{{See also|Organophosphate-induced delayed neuropathy}}
Many "organophosphates" are potent nerve agents, functioning by inhibiting the action of acetylcholinesterase (AChE) in nerve cells. They are one of the most common causes of poisoning worldwide, and are frequently intentionally used in suicides in agricultural areas. Organophosphate pesticides can be absorbed by all routes, including inhalation, ingestion, and dermal absorption. Their inhibitory effects on the acetylcholinesterase enzyme lead to a pathological excess of acetylcholine in the body. Their toxicity is not limited to the acute phase, however, and chronic effects have long been noted. Neurotransmitters such as acetylcholine (which is affected by organophosphate pesticides) are profoundly important in the brain's development, and many organophosphates have [[neurotoxic]] effects on developing organisms, even from low levels of exposure. Other organophosphates are not toxic, yet their main metabolites, such as their [[Oxon (chemical)|oxon]]s, are. Treatment includes both a [[pralidoxime]] binder and an [[anticholinergic]] such as [[atropine]].


In addition to their use as hydraulic base-stock, organophosphates (tricresyl phosphate) and metal organothiophosphates ([[zinc dithiophosphate]]) are used as both an [[antiwear additive]]s and [[extreme pressure additive]]s in [[lubricant]]s, where they remain effective even at high temperatures.<ref>{{cite journal |last1=Guan |first1=Bihan |last2=Pochopien |first2=Bernadeta A. |last3=Wright |first3=Dominic S. |title=The chemistry, mechanism and function of tricresyl phosphate (TCP) as an anti‐wear lubricant additive |journal=Lubrication Science |date=August 2016 |volume=28 |issue=5 |pages=257–265 |doi=10.1002/ls.1327}}</ref><ref>{{cite journal |last1=Johnson |first1=David |last2=Hils |first2=John |title=Phosphate Esters, Thiophosphate Esters and Metal Thiophosphates as Lubricant Additives |journal=Lubricants |date=18 December 2013 |volume=1 |issue=4 |pages=132–148 |doi=10.3390/lubricants1040132}}</ref><ref>{{cite journal |last1=Li |first1=Haogang |last2=Zhang |first2=Yanbin |last3=Li |first3=Changhe |last4=Zhou |first4=Zongming |last5=Nie |first5=Xiaolin |last6=Chen |first6=Yun |last7=Cao |first7=Huajun |last8=Liu |first8=Bo |last9=Zhang |first9=Naiqing |last10=Said |first10=Zafar |last11=Debnath |first11=Sujan |last12=Jamil |first12=Muhammad |last13=Ali |first13=Hafiz Muhammad |last14=Sharma |first14=Shubham |title=Extreme pressure and antiwear additives for lubricant: academic insights and perspectives |journal=The International Journal of Advanced Manufacturing Technology |date=May 2022 |volume=120 |issue=1-2 |pages=1–27 |doi=10.1007/s00170-021-08614-x}}</ref>
===Chronic toxicity===
Repeated or prolonged exposure to organophosphates may result in the same effects as acute exposure including the delayed symptoms. Other effects reported in workers repeatedly exposed include impaired memory and concentration, disorientation, severe depression, irritability, confusion, headache, speech difficulties, delayed reaction times, nightmares, sleepwalking, drowsiness, or insomnia. An influenza-like condition with headache, nausea, weakness, loss of appetite, and malaise has also been reported.<ref>{{cite web |title= PARATHION |work= Pesticide Information Profiles |publisher= Extension Toxicology Network |date= Sep 1993 |url= http://extoxnet.orst.edu/pips/parathio.htm |url-status= live |archive-url= https://web.archive.org/web/20070722085944/http://extoxnet.orst.edu/pips/parathio.htm |archive-date= 2007-07-22 }}</ref>


===Metal extractants===
The physiological difference of OPEs in size and polarity greatly influences the physical and biochemical toxicity of the compound group.<ref name=":3" /> The chemical structures of OP triesters used as flame retardants and plasticizers are essentially similar to those of OP insecticides that target the nervous system of insects.<ref name=":7" /> Multiple toxicological studies have shown that OPEs such as TBOEP, TCIPP, TDCIPP, triethyl phosphate (TEP), and tris(methylphenyl)phosphate (TMPP) elicit effects on embryonic development, mRNA expression, thyroid hormones, circulating bile acid concentrations, and the neurological system in fish, birds, rodents, and/or humans.<ref>{{Cite journal|last1=Greaves|first1=Alana K.|last2=Letcher|first2=Robert J.|date=2014-07-15|title=Comparative Body Compartment Composition and In Ovo Transfer of Organophosphate Flame Retardants in North American Great Lakes Herring Gulls|url=https://pubs.acs.org/doi/10.1021/es501334w|journal=Environmental Science & Technology|language=en|volume=48|issue=14|pages=7942–7950|doi=10.1021/es501334w|pmid=24905208|bibcode=2014EnST...48.7942G|issn=0013-936X}}</ref>
Organophosphates have long been used in the field of [[extractive metallurgy]] to liberate valuable [[rare earth]]s from their [[ore]]s.<ref>{{cite journal |last1=Hidayah |first1=Nur Nadiatul |last2=Abidin |first2=Sumaiya Zainal |title=The evolution of mineral processing in extraction of rare earth elements using liquid-liquid extraction: A review |journal=Minerals Engineering |date=June 2018 |volume=121 |pages=146–157 |doi=10.1016/j.mineng.2018.03.018}}</ref> [[Di(2-ethylhexyl)phosphoric acid]] and [[tributyl phosphate]] are used for the [[liquid–liquid extraction]] of these elements from the acidic mixtures form by the [[Leaching (metallurgy)|leaching]] of mineral deposits.<ref>{{cite journal |last1=Xie |first1=Feng |last2=Zhang |first2=Ting An |last3=Dreisinger |first3=David |last4=Doyle |first4=Fiona |title=A critical review on solvent extraction of rare earths from aqueous solutions |journal=Minerals Engineering |date=February 2014 |volume=56 |pages=10–28 |doi=10.1016/j.mineng.2013.10.021 |doi-access=free}}</ref> These compounds are also used for the [[PUREX]] (plutonium uranium reduction extraction) process, which is used for [[nuclear reprocessing]].<ref>{{cite journal|title=Recent advances on the chemistry of solvent extraction applied to the reprocessing of spent nuclear fuels and radioactive wastes|author1=Paiva, A. P. |author2=Malik, P.|journal=Journal of Radioanalytical and Nuclear Chemistry|year=2004|volume=261|issue=2|pages=485–496|doi=10.1023/B:JRNC.0000034890.23325.b5|s2cid=94173845 }}</ref>


===Low-level exposure===
===Surfactants===
Mono- and di- phosphate esters of alcohols or alcohol [[ethoxylate]]s are used as [[surfactant]]s.<ref name="Farn2008">{{cite book | last=Farn | first=R.J. | title=Chemistry and Technology of Surfactants | publisher=Wiley | year=2008 | isbn=978-1-4051-7179-3 | url=https://books.google.co.uk/books?id=CCn81pnPrgwC&pg=PP2 | access-date=2023-05-27 | pages=122-124}}</ref> Compared to the more common sulfur-based anionic surfactants (such as [[Alkylbenzene sulfonates|LAS]] or [[Sodium laureth sulfate|SLES]]), phosphate ester surfactants are more expensive and generate less foam.<ref name="Farn2008" /> Benefits include stability over a broad pH range, low skin irritation and a high tolerance to dissolved salts.<ref>{{cite journal |last1=Arora |first1=Pinklesh |last2=Singh |first2=Rakhi |last3=Seshadri |first3=Geetha |last4=Tyagi |first4=Ajay Kumar |title=Synthesis, Properties and Applications of Anionic Phosphate Ester Surfactants: A Review |journal=Tenside Surfactants Detergents |date=16 July 2018 |volume=55 |issue=4 |pages=266–272 |doi=10.3139/113.110570}}</ref>
Even at relatively low levels, organophosphates may be hazardous to human health.<ref>{{Citation |date=2015-03-16 |url=http://dx.doi.org/10.1201/b18221-21 |work=Everyday Environmental Toxins |pages=232–251 |publisher=Apple Academic Press |doi=10.1201/b18221-21 |access-date=2022-08-23|title=- Seven-Year Neurodevelopmental Scores and Prenatal Exposure to Chlorpyrifos, A Common Agricultural Pesticide |isbn=9780429162145 |hdl=20.500.12648/7724 |hdl-access=free }}</ref> These pesticides act on [[acetylcholinesterase]],<ref>{{cite web|title=Organophosphates FAQs|url=https://www.cdc.gov/nceh/clusters/fallon/organophosfaq.htm|website=Centers for Disease Control and Prevention|publisher=DHHS Department of Health and Human Services|access-date=6 February 2016|url-status=live|archive-url=https://web.archive.org/web/20160120233638/http://www.cdc.gov/nceh/clusters/fallon/organophosfaq.htm|archive-date=20 January 2016}}</ref> an enzyme found in the brain. Thus, fetuses and young children, whose brain development depends on a strict sequence of biological events, may be most at risk.<ref>{{cite journal |last1= Jurewicz |first1= Joanna |last2= Hanke |first2= Wojciech |title= Prenatal and Childhood Exposure to Pesticides and Neurobehavioral Development: Review of Epidemiological Studies |journal= International Journal of Occupational Medicine and Environmental Health |volume= 21 |issue= 2 |pages= 121–132 |publisher= Versita, Warsaw |date= 9 Jul 2008 |url= http://versita.metapress.com/content/g4470858487t28u4/ |archive-url= https://archive.today/20120717203917/http://versita.metapress.com/content/g4470858487t28u4/ |url-status= dead |archive-date= 17 July 2012 |doi= 10.2478/v10001-008-0014-z |issn= 1896-494X |pmid= 18614459 }}</ref> They can be absorbed through the lungs or skin or by eating them on food. According to a 2008 report from the U.S. Department of Agriculture, ″detectable″ traces of organophosphate were found in a representative sample of produce tested by the agency, 28% of frozen blueberries, 20% of celery, 27% of green beans, 17% of peaches, 8% of broccoli, and 25% of strawberries.<ref>{{cite news |url=http://www.cnn.com/2010/HEALTH/05/17/pesticides.adhd/ |work=CNN |title=Study: ADHD linked to pesticide exposure |date=17 May 2010 |url-status=live |archive-url=https://web.archive.org/web/20100518101356/http://www.cnn.com/2010/HEALTH/05/17/pesticides.adhd/ |archive-date=18 May 2010 }}</ref>
In agricultural settings monoesters of fatty alcohol ethoxylates are used, which are able to disperse poorly miscible or insoluble pesticides into water. As they are low-foaming these mixtures can be sprayed effectively onto fields, while a high salt tolerance allows co-spraying of pesticides and inorganic fertilisers.<ref >{{cite book | last=Kaneko | first=T.M. | last2=Spicer | first2=L.D. | title=Pesticide Formulations and Application Systems: Fourth Symposium : a Symposium Sponsored by ASTM Committee E-35 on Pesticides, New Orleans, La., 2-3 Nov. 1983 | publisher=ASTM | series=ASTM special technical publication | issue=no. 875, v. 4 | year=1985 | isbn=978-0-8031-0413-6 | url=https://books.google.co.uk/books?id=NSvmvgBsn8cC&pg=PA5 | access-date=2023-05-27 | pages=5-14}}</ref>
Low-levels of phosphate mono-esters, such as [[potassium cetyl phosphate]], find use in cosmetic creams and lotions.<ref>{{cite journal |last1=Miller |first1=Dennis |last2=Wiener |first2=Eva-Maria |last3=Turowski |first3=Angelika |last4=Thunig |first4=Christine |last5=Hoffmann |first5=Heinz |title=O/W emulsions for cosmetics products stabilized by alkyl phosphates — rheology and storage tests |journal=Colloids and Surfaces A: Physicochemical and Engineering Aspects |date=July 1999 |volume=152 |issue=1-2 |pages=155–160 |doi=10.1016/S0927-7757(98)00630-X}}</ref> These in oil-in-water formulations are primarily based on non-ionic surfactants, with the anionic phosphate acting as emulsion-stabilisers. Phosphate tri-esters such as [[tributyl phosphate]] are used as [[anti-foaming agent]] in paints and concrete.


===Cancer===
===Nerve agents===
{{main|Nerve agents}}
Although the first phosphorous compounds observed to act as cholinesterase inhibitors were organophosphates,<ref>{{cite journal |last=Petroianu |first=G. A. |date=2010-10-01 |title=Toxicity of phosphor esters: Willy Lange (1900-1976) and Gerda von Krueger (1907-after 1970) |journal=Die Pharmazie |volume=65 |issue=10 |pages=776–780 |issn=0031-7144 |pmid=21105582}}</ref> the vast majority of nerve agents are instead [[phosphonate]]s containing a P-C bond. Only a handful of organophosphate nerve agents were developed between the 1930s and 1960s, including [[diisopropylfluorophosphate]], [[VG (nerve agent)|VG]] and [[Neopentylene fluorophosphate|NPF]]. Between 1971 and 1993 the [[Soviet Union]] developed many new potential nerve agents, commonly known as the [[Novichok agents]].<ref>{{cite journal |last1=Chai |first1=Peter R. |last2=Hayes |first2=Bryan D. |last3=Erickson |first3=Timothy B. |last4=Boyer |first4=Edward W. |title=Novichok agents: a historical, current, and toxicological perspective |journal=Toxicology Communications |date=January 2018 |volume=2 |issue=1 |pages=45–48 |doi=10.1080/24734306.2018.1475151 |pmid=30003185 |pmc=6039123 |s2cid=49661943 }}</ref> Some of these can be considered organophosphates (in a broad sense), being derivatives of [[fluorophosphoric acid]]. Examples include [[A-232]], [[A-234]], [[A-262]], [[C01-A035]] and [[C01-A039]]. The most notable of these in A-234, which was claimed to be responsible for the [[poisoning of Sergei and Yulia Skripal]] in Salisbury (UK) 2018.<ref>{{cite journal |last1=Vale |first1=J. Allister |last2=Marrs |first2=Timothy C. |last3=Maynard |first3=Robert L. |title=Novichok: a murderous nerve agent attack in the UK |journal=Clinical Toxicology |date=2 November 2018 |volume=56 |issue=11 |pages=1093–1097 |doi=10.1080/15563650.2018.1469759}}</ref>


==In nature==
The United States Environmental Protection Agency lists parathion as a possible human [[carcinogen]].<ref>{{cite web |title= Parathion (CASRN 56-38-2) |work= IRIS Summaries |publisher= U.S. EPA |date= 9 Aug 2012 |url= http://www.epa.gov/iris/subst/0327.htm |url-status= live |archive-url= https://web.archive.org/web/20061010065849/http://www.epa.gov/iris/subst/0327.htm |archive-date= 2006-10-10 }}</ref> The [[International Agency for Research on Cancer]] (IARC), found that some organophosphates may increase cancer risk.<ref name=IARC112>{{Cite web|url=https://www.iarc.fr/en/media-centre/iarcnews/pdf/MonographVolume112.pdf|title=IARC Monographs Volume 112: evaluation of five organophosphate insecticides and herbicides|website=World Health Organization|archive-url=https://web.archive.org/web/20170417003550/https://www.iarc.fr/en/media-centre/iarcnews/pdf/MonographVolume112.pdf|archive-date=2017-04-17|url-status=live}}</ref> [[Tetrachlorvinphos]] and [[parathion]] were classified as "possibly carcinogenic", whereas [[malathion]] and [[diazinon]] were classified as probably carcinogenic to humans.<ref>{{cite web |url=https://www.iarc.fr/en/media-centre/iarcnews/pdf/MonographVolume112.pdf |title=Archived copy |access-date=2016-05-20 |url-status=live |archive-url=https://web.archive.org/web/20170417003550/https://www.iarc.fr/en/media-centre/iarcnews/pdf/MonographVolume112.pdf |archive-date=2017-04-17 }}</ref>
The detection of OPEs in the air as far away as Antarctica at concentrations around 1&nbsp;ng/m<sup>3</sup> suggests their persistence in air, and their potential for long-range transport.<ref name=":7" /> OPEs were measured in high frequency in air and water and widely distributed in northern hemisphere.<ref>{{Cite journal|last1=Salamova|first1=Amina|last2=Ma|first2=Yuning|last3=Venier|first3=Marta|last4=Hites|first4=Ronald A.|date=2014-01-14|title=High Levels of Organophosphate Flame Retardants in the Great Lakes Atmosphere|url=https://doi.org/10.1021/ez400034n|journal=Environmental Science & Technology Letters|volume=1|issue=1|pages=8–14|doi=10.1021/ez400034n}}</ref><ref name=":8">{{Cite journal|last1=Venier|first1=Marta|last2=Dove|first2=Alice|last3=Romanak|first3=Kevin|last4=Backus|first4=Sean|last5=Hites|first5=Ronald|date=2014-08-19|title=Flame Retardants and Legacy Chemicals in Great Lakes' Water|url=https://pubs.acs.org/doi/10.1021/es501509r|journal=Environmental Science & Technology|language=en|volume=48|issue=16|pages=9563–9572|doi=10.1021/es501509r|pmid=25045802|bibcode=2014EnST...48.9563V|issn=0013-936X}}</ref> The chlorinated OPEs (TCEP, TCIPP, TDCIPP) in urban sampling sites and non-halogenated like TBOEP in rural areas respectively were frequently measured in the environment across multiple sites. In the Laurentian Great Lakes total OPEs concentrations were found to be 2–3 orders of magnitude higher than concentrations of brominated flame retardants measured in similar air.<ref name=":8" /> Waters from rivers in Germany, Austria, and Spain have been consistently recorded for TBOEP and TCIPP at highest concentrations.<ref name=":7" /> From these studies, it is clear that OPE concentrations in both air and water samples are often orders of magnitude higher than other flame retardants, and that concentrations are largely dependent on sampling location, with higher concentrations in more urban, polluted locations.

===Health effects on children===

A 2013 review of 27 studies on prenatal and early childhood exposures to organophosphate pesticides found all but one showed negative neurodevelopmental outcomes. In the ten studies that assessed prenatal exposure, "cognitive deficits (related to working memory) were found in children at age 7 years, behavioral deficits (related to attention) seen mainly in toddlers, and motor deficits (abnormal reflexes), seen mainly in neonates."<ref>{{cite journal |title=Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: a systematic review. |journal=Neurotoxicology |volume=39 |pages=158–68 |pmid=24121005 |pmc=3899350 |year=2013 |last1=Muñoz-Quezada |first1=M. T. |last2=Lucero |first2=B. A. |last3=Barr |first3=D. B. |last4=Steenland |first4=K. |last5=Levy |first5=K. |last6=Ryan |first6=P. B. |last7=Iglesias |first7=V. |last8=Alvarado |first8=S. |last9=Concha |first9=C. |last10=Rojas |first10=E. |last11=Vega |first11=C. |doi=10.1016/j.neuro.2013.09.003 }}</ref>

A [[systematic review]] of neurodevelopmental effects of prenatal and postnatal organophosphate pesticide exposure was done in 2014. The review found that "Most of the studies evaluating prenatal exposure observed a negative effect on mental development and an increase in attention problems in preschool and school children."<ref>{{cite journal |title=A systematic review of neurodevelopmental effects of prenatal and postnatal organophosphate pesticide exposure. |journal=Toxicology Letters |volume=230 |issue=2 |pages=104–21 |pmid=24291036 |year=2014 |last1=González-Alzaga |first1=B. |last2=Lacasaña |first2=M. |last3=Aguilar-Garduño |first3=C. |last4=Rodríguez-Barranco |first4=M. |last5=Ballester |first5=F. |last6=Rebagliato |first6=M. |last7=Hernández |first7=A. F. |doi=10.1016/j.toxlet.2013.11.019 }}</ref>

In the US the organophosphate [[phosmet]] was banned for use on household fruit trees, ornamentals, and domestic pets in 2001 as other pesticides became available for these uses. Many other uses of phosmet were still allowed, especially commercial ones.<ref>{{cite journal |title=Phosmet (Imidan) |url=https://agrilife.org/aes/files/2010/06/December-02-Chemogram2.pdf |journal=Chemogram |pages=2 |date=December 2002 |last1=Holloway |first1=Rodney L. }}</ref>

==Affected populations==
According to the [[United States Environmental Protection Agency|EPA]], organophosphate use in 2004 accounts for 40% of all insecticide products used in the United States.<ref name=":1">{{Cite journal|url=https://ehp.niehs.nih.gov/1206015/|title=Environmental Health Perspectives – Population-Based Biomonitoring of Exposure to Organophosphate and Pyrethroid Pesticides in New York City|journal=Environmental Health Perspectives|date=January 2013 |volume=121 |issue=11–12 |pages=1349–1356 |doi=10.1289/ehp.1206015 |language=en-US|access-date=2017-04-24|url-status=live|archive-url=https://web.archive.org/web/20170428170626/https://ehp.niehs.nih.gov/1206015/|archive-date=2017-04-28|last1=McKelvey |first1=Wendy |last2=Jacobson |first2=J. Bryan |last3=Kass |first3=Daniel |last4=Barr |first4=Dana Boyd |last5=Davis |first5=Mark |last6=Calafat |first6=Antonia M. |last7=Aldous |first7=Kenneth M. |pmid=24076605 |pmc=3855501 }}</ref>&nbsp;Out of concerns for potential hazards of organophosphate exposure to child development, the EPA began phasing out forms of organophosphates used indoors in 2001.<ref name=":1" /> While it is used in forestry, urban, and public health spraying (mosquito abatement programs, etc.) as well, the general population has been observed to have low exposure.<ref>{{cite web|url=https://www.iarc.fr/en/media-centre/iarcnews/pdf/MonographVolume112.pdf|title=IARC Monographs Volume 112: evaluation of five organophosphate insecticides and herbicides|website=iarc.fr|access-date=29 April 2018|url-status=live|archive-url=https://web.archive.org/web/20170417003550/https://www.iarc.fr/en/media-centre/iarcnews/pdf/MonographVolume112.pdf|archive-date=17 April 2017}}</ref> Thus, the primary affected population that faces exposure to organophosphates are farmworkers, especially those in countries that have fewer restrictions on its usage, such as in India.<ref>{{Cite news|url=http://news.nationalgeographic.com/news/2013/07/130718-organophosphates-pesticides-indian-food-poisoning/|title=Organophosphates: A Common But Deadly Pesticide|date=2013-07-18|access-date=2017-04-24|url-status=dead|archive-url=https://web.archive.org/web/20170409175551/http://news.nationalgeographic.com/news/2013/07/130718-organophosphates-pesticides-indian-food-poisoning/|archive-date=2017-04-09}}</ref>

===Farmworkers in the United States===
In the United States, migrant and seasonal farmworkers are the most susceptible to organophosphate exposure. Of the U.S. farmworker population, there are about 4.2 million seasonal or migrant men, women, and even children, 70% of whom are born in Mexico and an overwhelming 90% majority of these are Latino.<ref>{{Cite journal|last1=Arcury|first1=T A|last2=Quandt|first2=S A|last3=Dearry|first3=A|date=2017-04-24|title=Farmworker pesticide exposure and community-based participatory research: rationale and practical applications.|journal=Environmental Health Perspectives|volume=109|issue=Suppl 3|pages=429–434|issn=0091-6765|pmc=1240561|pmid=11427392|doi=10.1289/ehp.01109s3429}}</ref> This almost homogenous racial aspect of employment in farm work in the United States highly suggests social, economic, and political factors undercurrents that would explain their vulnerability.<ref>[http://scholarship.law.ufl.edu/facultypub/268 Joan D. Flocks, e Environmental and Social Injustice of Farmworker Pesticide Exposure], 19 Geo. J. on Poverty L. & Pol'y 255 (2012).</ref> Half of the farmworker population in the United States do not have legal documentation and two thirds live in poverty, making it difficult to fully understand and document the characteristics of this population with relative certainty.<ref>{{Cite journal|title=The Health of U.S. Hired Farm Workers |journal = Annual Review of Public Health|volume = 24|pages = 175–193|last=Villarejo|first=Don|date=2003-11-28|language=en|doi=10.1146/annurev.publhealth.24.100901.140901| doi-access=free |pmid = 12359914}}</ref> Furthermore, the group faces linguistic barriers, with about 70% of the migrant seasonal farmworker population reporting that they cannot speak English well.<ref>''Farmworker Health Factsheet''. N.p.: National Center For Farmworker Health, Aug. 2012. PDF. {{cite web |url=http://www.ncfh.org/uploads/3/8/6/8/38685499/fs-facts_about_farmworkers.pdf |title=Archived copy |access-date=2017-04-24 |url-status=live |archive-url=https://web.archive.org/web/20150922001717/http://www.ncfh.org/uploads/3/8/6/8/38685499/fs-facts_about_farmworkers.pdf |archive-date=2015-09-22 }}&nbsp;</ref>&nbsp;

In the United States, poverty and lack of documentation status puts migrant farmworkers in housing situations that make them far more likely to contract infectious or parasitic diseases and to suffer from chemical related ailments than the general U.S. population.<ref name=":2">{{Cite journal|last1=Hansen|first1=Eric|last2=Donohoe|first2=Martin|date=2003-05-01|title=Health issues of migrant and seasonal farmworkers|journal=Journal of Health Care for the Poor and Underserved|volume=14|issue=2|pages=153–164|issn=1049-2089|pmid=12739296|doi=10.1353/hpu.2010.0790|s2cid=37962307}}</ref>&nbsp;Field workers who are exposed to pesticides continue to further expose their families in their residences, especially through contaminated clothing in which the residue settles as house dust.<ref name=":2" /> Increased rates of a full range of adverse birth outcomes result from high exposure to pesticides in a study of 500,000 births among farm workers in California's San Joaquin Valley.<ref>{{Cite journal|last1=Larsen|first1=Ashley|last2=Gaines|first2=Steven|date=2017-08-29|title=Agricultural pesticide use and adverse birth outcomes in the San Joaquin Valley of California|journal=Nature Communications|volume=8|issue=1|pages=302|issn=2041-1723|pmid=28851866|pmc=5575123|doi=10.1038/s41467-017-00349-2|bibcode=2017NatCo...8..302L}}</ref>

Economic, social, racial, and political barriers make passing policy and creating protective measures less likely to occur; in the context of their jobs, migrant seasonal farm workers are structurally vulnerable to exploitation and working conditions that are Occupational Factors not up to health standards if they are unable to find the necessary physical and social resources to protect themselves.<ref>{{Cite journal|last1=Quesada|first1=James|last2=Hart|first2=Laurie K.|last3=Bourgois|first3=Philippe|date=2017-04-24|title=Structural Vulnerability and Health: Latino Migrant Laborers in the United States|journal=Medical Anthropology|volume=30|issue=4|pages=339–362|doi=10.1080/01459740.2011.576725|issn=0145-9740|pmc=3146033|pmid=21777121}}</ref>&nbsp; &nbsp;&nbsp;

The nature of their job may require constant exposure to toxins and pesticides and subjects them to increasingly extreme weather as climate change progresses. Thus, migrant farm work has been ranked conservatively as possibly the second most dangerous job in the country.<ref>{{Cite web|url=https://www.pbs.org/now/politics/migrants.html|title=NOW with Bill Moyers. Politics & Economy. On the Border. Migrant Labor in United States {{!}} PBS|website=www.pbs.org|access-date=2017-04-24|url-status=live|archive-url=https://web.archive.org/web/20170506054339/http://www.pbs.org/now/politics/migrants.html|archive-date=2017-05-06}}</ref>

==Regulatory efforts==
Organophosphates (OPs) were among the most widely used insecticides until the 21st century.<ref name=npic>{{cite book|last1=Roberts|first1=J.R.|last2=Reigart|first2=J.R.|title=Recognition and Management of Pesticide Poisonings|date=2013|publisher=Environmental Protection Agency|page=43|edition=6th|url=http://npic.orst.edu/RMPP/rmpp_main2a.pdf|access-date=10 March 2018|url-status=live|archive-url=https://web.archive.org/web/20170513145709/http://npic.orst.edu/RMPP/rmpp_main2a.pdf|archive-date=13 May 2017}}</ref> And until the mid 1990s, general pesticide regulation was dependent on the Federal Food, Drug and Cosmetic Act (FFDCA) and the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) passed in 1938 and 1947, respectively.<ref name="ehp"/> In 1993, the Environmental Protection Agency (EPA) was bound by a pledge made to Congress to significantly reduce the amount of pesticides used in the United States, and the U.S. Department of Agriculture, along with the Food and Drug Administration, joined the EPA in this commitment.<ref name="agri">{{cite journal|last1=Fenske|first1=R.|title=Organophosphates and the Risk Cup|journal=Agrichemical and Environmental News|date=November 1999|issue=163|pages=6–8|url=http://nasdonline.org/1710/d001833/organophosphates-and-the-risk-cup.html|access-date=10 March 2018|url-status=live|archive-url=https://web.archive.org/web/20180311141005/http://nasdonline.org/1710/d001833/organophosphates-and-the-risk-cup.html|archive-date=11 March 2018}}</ref> Then, in 1996, The Food Quality Protection Act (FQPA) was signed into law to strengthen the regulation of pesticide in food and make regulation practices more consistent.<ref name="ehp">{{cite journal|last1=Clune|first1=A.L.|last2=Ryan|first2=P.B.|last3=Barr|first3=D.B.|title=Have Regulatory Efforts to Reduce Organophosphorus Insecticide Exposures Been Effective?|journal=Environmental Health Perspectives|date=April 2012|volume=120|issue=4|pages=521–525|doi=10.1289/ehp.1104323|pmid=22251442|pmc=3339465}}</ref> One way that this strengthening was accomplished was through mandating aggregate and cumulative exposure risk assessments in derivative food tolerance levels.<ref name="ehp"/> The EPA selected OPs as the first class of pesticides for assessing food tolerances because of their specific toxicity behavior as acetylcholinesterase inhibitors.<ref name="ehp"/>

Between 1996 and 1999, the use of OPs actually increased (despite the passing of the FQPA) from 75 million to 91 million pounds per year.<ref name= "ehp"/> However, this is mainly due to the cotton boll weevil eradication program through the U.S Department of Agriculture and the use of OPs eventually decreased to 46 million pounds per year by 2004.<ref name= "ehp"/> The residential use of OP pesticides may have declined more quickly, when compared to commercial use, largely due to the voluntary cancellation of chlorpyrifos and diazinon as approved pesticides for home use.<ref name="ehp"/> The phaseout of both chlorpyrifos and diazinon for most residential uses was complete in 2005.<ref name="ehp"/>

Parathion (Ethyl) use is banned or restricted in 23 countries and its import is illegal in a total of 50 countries.<ref name="pmep">{{cite web |title= Parathion (Ethyl) - Remaining Use Canceled 9/00 |work= Pesticide Active Ingredient Information |publisher= Cornell University |date= 13 Oct 2000 |url= http://pmep.cce.cornell.edu/profiles/insect-mite/mevinphos-propargite/parathion/parath_can_0900.html |url-status= live |archive-url= https://web.archive.org/web/20110927044246/http://pmep.cce.cornell.edu/profiles/insect-mite/mevinphos-propargite/parathion/parath_can_0900.html |archive-date= 2011-09-27 }}</ref> Its use was banned in the U.S. in 2000 and it has not been used since 2003.<ref name="pmep"/>

In 2001, the EPA placed new restrictions on the use of the organophosphates phosmet and azinphos-methyl to increase protection of agricultural workers.{{citation needed|date=March 2018}} The crop uses reported at that time as being phased out in four years included those for almonds, tart cherries, cotton, cranberries, peaches, pistachios, and walnuts.{{citation needed|date=March 2018}} The crops with time-limited registration included apples/crab apples, blueberries, sweet cherries, pears, pine seed orchards, brussels sprouts, cane berries, and the use of azinphos-methyl by nurseries for quarantine requirements.<ref>{{cite news |last= Hess |first= Glenn |title= US EPA restricts pesticides azinphos-methyl, phosmet |publisher= ICIS.com |date= 1 Nov 2011 | url =http://www.icis.com/Articles/2001/11/01/150226/us-epa-restricts-pesticides-azinphos-methyl-phosmet.html }}</ref> The labeled uses of phosmet include alfalfa, orchard crops (e.g. almonds, walnuts, apples, cherries), blueberries, citrus, grapes, ornamental trees (not for use in residential, park, or recreational areas) and nonbearing fruit trees, Christmas trees and conifers (tree farms), potatoes, and peas.<ref>{{cite web |last1= Peck |first1= Chuck |last2= Aubee |first2= Catherine |title= Risks of Phosmet Use to the Federally Threatened and Endangered California Tiger Salamander (Ambystoma californiense) |work= Pesticide Effects Determinations |publisher= Environmental Fate and Effects Division, Office of Pesticide Programs |date= 29 Mar 2010 |url= http://www.epa.gov/espp/litstatus/effects/redleg-frog/2010/phosmet/assessment.pdf |url-status= live |archive-url= https://web.archive.org/web/20110204104419/http://www.epa.gov/espp/litstatus/effects/redleg-frog/2010/phosmet/assessment.pdf |archive-date= 2011-02-04 }}</ref> Azinphos-methyl has been banned in Europe since 2006.<ref>{{cite news |last= Scott |first= Alex |title= Europe Rejects Appeal for Use of Azinphos-methyl Pesticide |publisher= IHS Chemical Week |date= 4 Aug 2008 |url= http://www.chemweek.com/envirotech/regulatory/13435.html |url-status= live |archive-url= https://web.archive.org/web/20110708141949/http://www.chemweek.com/envirotech/regulatory/13435.html |archive-date= 2011-07-08 }}</ref>

In May 2006, the Environmental Protection Agency (EPA) reviewed the use of [[dichlorvos]] and proposed its continued sale, despite concerns over its safety and considerable evidence suggesting it is carcinogenic and harmful to the brain and nervous system, especially in children.{{citation needed|date=March 2018}} Environmentalists charge that the latest decision was the product of backroom deals with industry and political interference.<ref>{{cite magazine |last= Raeburn |first= Paul |title= Slow-Acting |magazine= [[Scientific American]] |date= 14 Aug 2006 |url= http://www.scientificamerican.com/article.cfm?id=slow-acting |url-status= live |archive-url= https://web.archive.org/web/20130921112017/http://www.scientificamerican.com/article.cfm?id=slow-acting |archive-date= 2013-09-21 }}</ref>

As of 2013, thirty-six types of organophosphates were registered for use in the United States.<ref name="npic" /> Organophosphates are currently used in a variety of environments (e.g. agriculture, gardens and veterinary practices), however, several notable OPs have been discontinued for use.<ref name="npic" /> This includes parathion, which is no longer registered for any use, and chlorpyrifos (as mentioned previously), which is no longer registered for home use.<ref name="npic" /> And again, other than for agricultural use, the OP diazinon has been banned in the U.S.{{citation needed|date=March 2018}}

==See also==
* [[Activity-based protein profiling]] using organophosphate-containing activity-based probes
* [[Pesticide toxicity to bees]]
* [[Toxic oil syndrome]]
* [[Cholinesterase inhibitor]]


==References==
==References==
{{Reflist|2|refs=
{{Reflist|2|}}
<ref name="IRAC-MoAs-9.4">{{cite web|url=http://irac-online.org/documents/moa-classification/|title=IRAC Mode of Action Classification Scheme Version 9.4|website=IRAC ([[Insecticide Resistance Action Committee]])|type=pdf|date=March 2020}}</ref>
}}

==Further reading==
* {{cite journal |doi=10.1016/j.scitotenv.2017.09.223|title=Organophosphonates: A review on environmental relevance, biodegradability and removal in wastewater treatment plants |year=2018 |last1=Rott |first1=Eduard |last2=Steinmetz |first2=Heidrun |last3=Metzger |first3=Jörg W. |journal=Science of the Total Environment |volume=615 |pages=1176–1191 |pmid=29751423 |bibcode=2018ScTEn.615.1176R }}
* {{cite journal | pmid = 16337171 | doi=10.1016/j.cca.2005.10.008 | volume=366 | issue=1–2 | title=Current issues in organophosphate toxicology |date=April 2006 | author=Costa LG | journal=Clin. Chim. Acta | pages=1–13}}.
* [https://www.atsdr.cdc.gov/csem/cholinesterase/ ATSDR Case Studies in Environmental Medicine: Cholinesterase Inhibitors, Including Pesticides and Chemical Warfare Nerve Agents] U.S. [[Department of Health and Human Services]]
* [http://www.emedicine.com/neuro/topic286.htm Organophosphates - an article by Frances M Dyro, MD]
* [https://www.nytimes.com/2006/08/04/washington/04pest.html NYTimes: E.P.A. Recommends Limits On Thousands of Pesticides]
* [http://www.epa.gov/pesticides/cumulative/common_mech_groups.htm#op EPA OP pesticide site]
* Phase [https://web.archive.org/web/20150924035941/http://www.iom-world.org/pubs/IOM_TM9902a.pdf 1], [https://web.archive.org/web/20150924035958/http://www.iom-world.org/pubs/IOM_TM9902b.pdf 2], and [https://web.archive.org/web/20161006161211/http://www.iom-world.org/pubs/IOM_TM9902c.pdf 3] reports from "Epidemiological study of the relationships between exposure to organophosphate pesticides and indices of chronic peripheral neuropathy, and neuropsychological abnormalities in sheep farmers and dippers." [[Institute of Occupational Medicine]].


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[[Category:Organophosphates| ]]
[[Category:Organophosphates| ]]

Revision as of 00:40, 8 January 2024

General chemical structure of the organophosphate functional group

In organic chemistry, organophosphates (also known as phosphate esters, or OPEs) are a class of organophosphorus compounds with the general structure O=P(OR)3, a central phosphate molecule with alkyl or aromatic substituents.[1] They can be considered as esters of phosphoric acid.

Like most functional groups, organophosphates occur in a diverse range of forms,[2] with important examples including key biomolecules such as DNA, RNA and ATP, as well as many insecticides, herbicides, nerve agents and flame retardants. OPEs have been widely used in various products as flame retardants, plasticizers, and performance additives to engine oil. The popularity of OPEs as flame retardants came as a substitution for the highly regulated brominated flame retardants.[3] The low cost of production and compatibility to diverse polymers made OPEs to be widely used in industry including textile, furniture, electronics as plasticizers and flame retardants. These compounds are added to the final product physically rather than by chemical bond.[4] Due to this, OPEs leak into the environment more readily through volatilization, leaching, and abrasion.[5] OPEs have been detected in diverse environmental compartments such as air, dust, water, sediment, soil and biota samples at higher frequency and concentration.[1][5]

Synthesis

Alcoholysis of POCl3

Phosphorus oxychloride reacts readily with alcohols to give organophosphates. This is the dominant industrial route and is responsible for almost all organophosphate production.

O=PCl3 + 3 ROH → O=P(OR)3 + 3 HCl
Esterification of phosphoric acid

In stark contrast to carboxylic acids, phosphoric acid does not readily esterify with alcohols. The use of activating species such as trichloroacetonitrile[6][7] or acetic anhydride[8] permit mono-esters to be formed, but tri-substituted organophosphates cannot be made in this way.

OP(OH)3 + ROH → OP(OH)2(OR) + H2O
Oxidation of phosphite esters

Organophosphites can be easily oxidised to give organophosphates. This might normally be considered a specialised method for academic labs, however large quantities of organophosphites are produced as antioxidant stabilisers for plastics, with their gradual oxidation forming organophosphates in the human environment.[9]

P(OR)3 + [O] → OP(OR)3
Phosphorylation

The formation of organophosphates is an important part of biochemistry and living systems achieve this using a variety of enzymes. Phosphorylation is essential to the processes of both anaerobic and aerobic respiration, which involve the production of adenosine triphosphate (ATP), the "high-energy" exchange medium in the cell.

Properties

Bonding

The bonding in organophosphates has been a matter of prolonged debate; the phosphorous atom is classically hypervalent, as it possesses more bonds than the octet rule should allow.[10] The focus of debate is usually on the nature of the phosphoryl P=O bond, which displays (in spite of the common depiction) non-classical bonding, with a bond order somewhere between 1 and 2. Early papers explained the hypervalence in terms of d-orbital hybridisation, with the energy penalty of promoting electrons into the higher energy orbitals being off-set by the stabilisation of additional bonding.[11] Later advances in computational chemistry showed that d-orbitals played little significant role in bonding.[12][13] Current models rely on either negative hyperconjugation,[14] or a more complex arraignment with a dative-type bond from P to O, combined with back-donation from a 2p orbital on the oxygen.[13][15] These models agree with the experimental observations of the phosphoryl as being shorter than P-OR bonds[16] and much more polarised. It has been argued that a more accurate depiction is dipolar (i.e. (RO)3P+-O-),[17] which is similar to the depiction phosphorous ylides such as methylenetriphenylphosphorane. However in contrast to ylides, the phosphoryl group is unreactive and organophosphates are poor nucleophiles, despite the high concentration of charge on the phosphoryl oxygen. The polarisation accounts in part for the higher melting points of phosphates when compared to their corresponding phosphites. The bonding in penta-coordinate phosphoranes (i.e. P(OR)5) is entirely different and involves three-center four-electron bonds.

Acidity

Phosphate esters bearing OH groups are acidic. The pKa of the first OH group is typically between 1-2, with the second OH deprotonating at a pKa of 6-7.[18] This is great practical importance as it means that phosphate mono- and di-esters are negatively charged at physiological pH. This includes biomolecules such as DNA and RNA. The presence of this negative charge make these compound much more water soluble and more resistant to degradation by hydrolysis or other forms of nucleophilic attack.

Water solubility

The water solubility of organophosphates is important factor is important in biological, industrial and environmental settings. The wide variety of substitutes used in organophosphate esters results in great variations in physical properties. OPEs exhibit a wide range of octanol/water partition coefficients where log Kow values range from -0.98 up to 10.6.[3] The majority of OPEs used as flame retardants and plasticisers are tri-esters with positive log Kow values ranging between 1.44 and 9.49, signifying hydrophobicity.[3][19][5][20] Hydrophobic OPEs are more likely to be bioaccumulated and biomagnified in aquatic ecosystems.[4] Halogenated organophosphates tend to be denser than water and sink, causing them to accumulate in sediments.[21]

Industrial materials

Pesticides

Malathion, one of the first organophosphate insecticides. It remains important as a Vector control agent.

Organophosphates are best known for their use as pesticides. The vast majority are insecticides and are used either to protect crops, or as vector control agents to reduce the transmission of diseases spread by insects, such as mosquitoes. Health concerns have seen their use significantly decrease since the turn of the century.[22][23] Glyphosate is sometimes called an organophosphate, but is in-fact a phosphonate. It's chemistry, mechanism of toxicity and end-use as a herbicide are different from the organophosphate insecticides.

The development of organophosphate insecticides dates back to the 1930s and is generally credited to Gerhard Schrader.[24] At the time pesticides were largely limited to arsenic salts (calcium arsenate, lead arsenate and Paris green)[25] or pyrethrin plant extracts, all of which had major problems.[26] Schrader was seeking more effective agents, however while some organophosphates were found to be far more dangerous to insects than higher animals,[27] the potential effectiveness of others as chemical weapons did not go unnoticed. The development of organophosphate insecticides and the earliest nerve agents was conjoined, with Schrader also developing the nerve agents tabun and sarin. Organophosphate pesticides were not commercialised until after WWII. Parathion was among the first marketed, followed by malathion and azinphosmethyl . Although organophosphates were used in considerable qualities they were originally less important than organochlorine insecticides such as DDT, dieldrin, and heptachlor. When many of the organochlorines were banned in the 1970s, following the publishing of Silent Spring, organophosphates became the most important class of insecticides globally. Nearly 100 were commercialised, with the following being a varied selection:

Organophosphate insecticides are acetylcholinesterase inhibitors, and when introduced to an organism they act to fatally disrupt the transmission of nerve signals. The risk of human death through organophosphate poisoning[28] was obvious from the start and let to efforts to lower toxicity again mammals while not reducing efficacy again insects.[29][30]

The majority of organophosphate insecticides are organothiophosphates (P=S) or phosphorodiamidates (P-N), both of which are significantly weaker acetylcholinesterase inhibitors than the corresponding phosphates (P=O). They are 'activated' biologically by the exposed organism, via oxidative conversion of P=S to P=O,[31] hydroxylation,[32][33], or other related process which see them transformed into organophosphates. In mammals these transformations occur almost exclusively in the liver,[34] while in insects they take place in the gut and fat body.[35][36][37] As the transformations are handled by different enzymes in different classes of organism it is possible to find compounds which activate more rapidly and completely in insects, and thus display more targeted lethal action.

This selectivity is far from perfect and organophosphate insecticides remain acutely toxic to humans, with many thousands estimated to be killed each year due to intentional[38] or unintentional poisoning. Beyond their acute toxicity, exposure to organophosphates is associated with a number of heath risks, including organophosphate-induced delayed neuropathy (muscle weakness) and developmental neurotoxicity.[24][39][40] There is limited evidence that certain compounds cause cancer, including malathion and diazinon.[41] Children[42] and farmworkers[43] are considered to be at greater risk.

Pesticide regulation in the United States and the regulation of pesticides in the European Union have both been increasing restrictions on organophosphate pesticides since the 1990s, particularly when used for crop protection. The use of organophosphates has decreased considerably since that time, having been replaced by pyrethroids and neonicotinoids, which are effective a much lower levels.[44] Reported cases of organophosphate poisoning in the US have reduced during this period.[45][46] Regulation in the global south can be less extensive.[47][48]

In 2015, only 3 of the 50 most common crop-specific pesticides used in the US were organophosphates (Chlorpyrifos, Bensulide, Acephate),[49] of these Chlorpyrifos was banned in 2021.[50] No new organophosphate pesticides have been commercialised in the 21st century.[51] The situation in vector control is fairly similar, despite different risk trade-offs,[52] with the global use of organophosphate insecticides falling by nearly half between 2010 and 2019.[23] Pirimiphos-methyl, Malathion and Temefos are still important, primarily for the control of malaria in the Asia-Pacific region.[23] The continued use of these agents is being challenged by the emergence of insecticide resistance.[53]

Flame retardants

Flame retardants are added to materials to prevent combustion and to delay the spread of fire after ignition. Organophosphate flame retardants are part of a wider family of phosphorous-based agents which include organic phosphonate and phosphinate esters, in addition to inorganic salts.[54][55] When some prominent brominated flame retardant were banned in the early 2000s phosphorous-based agents were promoted as safer replacements. This has led to a large increase in their use, with an estimated 1 million tonnes of organophosphate flame retardants produced in 2018.[56] Safety concerns have subsequently been raised about some of these reagents,[57][58] with several under regulatory scrutiny.[59][60]

Organophosphate flame retardants were first developed in the first half of the twentieth century in the from of triphenyl phosphate, tricresyl phosphate and tributyl phosphate for use in plastics like cellulose nitrate and cellulose acetate.[61] Use in cellulose products is still significant, but the largest area of application is now in plasticized vinyl polymers, principally PVC. The more modern organophosphate flame retardants come in 2 major types; chlorinated aliphatic compounds or aromatic diphosphates.[54] The chlorinated compounds TDCPP, TCPP and TCEP are all involatile liquids, of which TCPP is perhaps the most important. They are used in polyurethane (soft furnishings), PVC (wire and cable) phenolic resins and epoxy resinss (varnishes, coatings and adhesives). The most important of the diphosphates is bisphenol-A bis(diphenyl phosphate), with related analogues based around resorcinol and hydroquinone. These are used in polymer blends of engineering plastics, such as PPO/HIPS and PC/ABS,[62] which are commonly used to make casing for electrical items like TVs, computers and home appliances.

Organophosphates act multifunctionally to retard fire in both the gas phase and condensed (solid) phase. Halogenated organophosphates are more active overall as their degradation products interfere with combustion directly in the gas phase. All organophosphates have activity in the condensed phase, by forming phosphorus acids which promote char formation, insulating the surface from heat and air.

Organophosphates were originally thought to be a safe replacements for brominated flame retardants, however many are now coming under regulatory pressure due to their apparent health risks.[60][63][64] The chlorinated organophosphates may be carcinogenic, while others such as tricresyl phosphate have necrotoxic properties.[65] Bisphenol-A bis(diphenyl phosphate) can hydrolyse to form Bisphenol-A which is under significant scrutiny as potential endocrine-disrupting chemical. Although their names imply that they are single discreet species the some compounds are produced as complex mixtures, for instance commercial grade TCPP can contain 7 different isomers,[66] while tricresyl phosphate can contain up to 10.[67] This makes their safety profiles harder to ascertain, as material from different producers can have different compositions.[68]

Plasticisers

Plasticisers are added to polymers and plastics to improve their flexibility and processability, giving a softer more easily deformable material. In this way brittle polymers can be made more durable. Organophosphates find use because they are multifunctional; primarily plasticising but also imparting flame resistance. The most frequently plasticised polymers are the vinyls (PVC, PVB, PVA and PVCA), as well as cellulose plastics (cellulose acetate, nitrocellulose and cellulose acetate butyrate).[69] PVC dominates the market, consuming 80-90% of global plasticiser production.[69][70] PVC can accept large amounts of plasticiser; a PVC item may be 70-80% plasticiser by mass in extreme cases, but loadings of between 0-50% are more common.[71] The main applications of these products are in wire and cable insulation, flexible pipe, automotive interiors, plastic sheeting, vinyl flooring, and toys.

Pure PVC is more than 60% chlorine by mass and difficult to burn, but its flammability increases the more it is plasticised.[72] Organophosphates can act as both plasticisers and flame retarders. Compounds used are typically triaryl or alkyl diaryl phosphates, with cresyl diphenyl phosphate and 2-ethylhexyl diphenyl phosphate being important respective examples type.[73] These are both liquids with high boiling points. Organophosphates are more expensive than traditional plasticisers and so tend used in combination with other plasticisers and flame retardants.[74]

Hydraulic fluids and lubricant additives

Similar to their use as plastisiers, organophosphates are well suited to use as hydraulic fluids due to their low freezing points and high boiling points, fire-resistance, non-corrosiveness, excellent boundary lubrication properties and good general chemical stability. The triaryl phosphates are the most important group, with tricresyl phosphate being the first to be commercialised in the 1940s, with trixylyl phosphate following shortly after. Butylphenyl diphenyl phosphate and propylphenyl diphenyl phosphate became available after 1960.[75]

In addition to their use as hydraulic base-stock, organophosphates (tricresyl phosphate) and metal organothiophosphates (zinc dithiophosphate) are used as both an antiwear additives and extreme pressure additives in lubricants, where they remain effective even at high temperatures.[76][77][78]

Metal extractants

Organophosphates have long been used in the field of extractive metallurgy to liberate valuable rare earths from their ores.[79] Di(2-ethylhexyl)phosphoric acid and tributyl phosphate are used for the liquid–liquid extraction of these elements from the acidic mixtures form by the leaching of mineral deposits.[80] These compounds are also used for the PUREX (plutonium uranium reduction extraction) process, which is used for nuclear reprocessing.[81]

Surfactants

Mono- and di- phosphate esters of alcohols or alcohol ethoxylates are used as surfactants.[82] Compared to the more common sulfur-based anionic surfactants (such as LAS or SLES), phosphate ester surfactants are more expensive and generate less foam.[82] Benefits include stability over a broad pH range, low skin irritation and a high tolerance to dissolved salts.[83] In agricultural settings monoesters of fatty alcohol ethoxylates are used, which are able to disperse poorly miscible or insoluble pesticides into water. As they are low-foaming these mixtures can be sprayed effectively onto fields, while a high salt tolerance allows co-spraying of pesticides and inorganic fertilisers.[84] Low-levels of phosphate mono-esters, such as potassium cetyl phosphate, find use in cosmetic creams and lotions.[85] These in oil-in-water formulations are primarily based on non-ionic surfactants, with the anionic phosphate acting as emulsion-stabilisers. Phosphate tri-esters such as tributyl phosphate are used as anti-foaming agent in paints and concrete.

Nerve agents

Although the first phosphorous compounds observed to act as cholinesterase inhibitors were organophosphates,[86] the vast majority of nerve agents are instead phosphonates containing a P-C bond. Only a handful of organophosphate nerve agents were developed between the 1930s and 1960s, including diisopropylfluorophosphate, VG and NPF. Between 1971 and 1993 the Soviet Union developed many new potential nerve agents, commonly known as the Novichok agents.[87] Some of these can be considered organophosphates (in a broad sense), being derivatives of fluorophosphoric acid. Examples include A-232, A-234, A-262, C01-A035 and C01-A039. The most notable of these in A-234, which was claimed to be responsible for the poisoning of Sergei and Yulia Skripal in Salisbury (UK) 2018.[88]

In nature

The detection of OPEs in the air as far away as Antarctica at concentrations around 1 ng/m3 suggests their persistence in air, and their potential for long-range transport.[20] OPEs were measured in high frequency in air and water and widely distributed in northern hemisphere.[89][90] The chlorinated OPEs (TCEP, TCIPP, TDCIPP) in urban sampling sites and non-halogenated like TBOEP in rural areas respectively were frequently measured in the environment across multiple sites. In the Laurentian Great Lakes total OPEs concentrations were found to be 2–3 orders of magnitude higher than concentrations of brominated flame retardants measured in similar air.[90] Waters from rivers in Germany, Austria, and Spain have been consistently recorded for TBOEP and TCIPP at highest concentrations.[20] From these studies, it is clear that OPE concentrations in both air and water samples are often orders of magnitude higher than other flame retardants, and that concentrations are largely dependent on sampling location, with higher concentrations in more urban, polluted locations.

References

  1. ^ a b Greaves, Alana K.; Letcher, Robert J.; Chen, Da; McGoldrick, Daryl J.; Gauthier, Lewis T.; Backus, Sean M. (2016-10-01). "Retrospective analysis of organophosphate flame retardants in herring gull eggs and relation to the aquatic food web in the Laurentian Great Lakes of North America". Environmental Research. 150: 255–263. Bibcode:2016ER....150..255G. doi:10.1016/j.envres.2016.06.006. ISSN 0013-9351. PMID 27322497.
  2. ^ Ung, Sosthène P.-M.; Li, Chao-Jun (2023). "From rocks to bioactive compounds: a journey through the global P( v ) organophosphorus industry and its sustainability". RSC Sustainability. 1 (1): 11–37. doi:10.1039/D2SU00015F.
  3. ^ a b c Veen, Ike van der; Boer, Jacob de (2012). "Phosphorus flame retardants: Properties, production, environmental occurrence, toxicity and analysis". Chemosphere. 88 (10): 1119–1153. Bibcode:2012Chmsp..88.1119V. doi:10.1016/j.chemosphere.2012.03.067. PMID 22537891.
  4. ^ a b Wang, Xiaolei; Zhong, Wenjue; Xiao, Bowen; Liu, Qing; Yang, Liping; Covaci, Adrian; Zhu, Lingyan (2019-04-01). "Bioavailability and biomagnification of organophosphate esters in the food web of Taihu Lake, China: Impacts of chemical properties and metabolism". Environment International. 125: 25–32. doi:10.1016/j.envint.2019.01.018. hdl:10067/1585250151162165141. ISSN 0160-4120. PMID 30690428.
  5. ^ a b c Wei, Gao-Ling; Li, Ding-Qiang; Zhuo, Mu-Ning; Liao, Yi-Shan; Xie, Zhen-Yue; Guo, Tai-Long; Li, Jun-Jie; Zhang, Si-Yi; Liang, Zhi-Quan (January 2015). "Organophosphorus flame retardants and plasticizers: Sources, occurrence, toxicity and human exposure". Environmental Pollution. 196: 29–46. doi:10.1016/j.envpol.2014.09.012. PMID 25290907.
  6. ^ Kasemsuknimit, Atthapol; Satyender, Apuri; Chavasiri, Warinthorn; Jang, Doo-Ok (20 September 2011). "Efficient Amidation and Esterification of Phosphoric Acid Using Cl3CCN/ Ph3P". Bulletin of the Korean Chemical Society. 32 (9): 3486–3488. doi:10.5012/bkcs.2011.32.9.3486.
  7. ^ Escobedo-Hinojosa, Wendy; Hammer, Stephan C.; Wissner, Julian L.; Hauer, Bernhard (2021). "Fast and easy synthesis of the non-commercially available standard isobutyl monophosphate (ammonium salt)". MethodsX. 8: 101455. doi:10.1016/j.mex.2021.101455. PMC 8374633. PMID 34430336.
  8. ^ Dueymes, Cyril; Pirat, Céline; Pascal, Robert (September 2008). "Facile synthesis of simple mono-alkyl phosphates from phosphoric acid and alcohols". Tetrahedron Letters. 49 (36): 5300–5301. doi:10.1016/j.tetlet.2008.06.083.
  9. ^ Liu, Runzeng; Mabury, Scott A. (19 February 2019). "Organophosphite Antioxidants in Indoor Dust Represent an Indirect Source of Organophosphate Esters". Environmental Science & Technology. 53 (4): 1805–1811. doi:10.1021/acs.est.8b05545. PMID 30657667. S2CID 58665691.
  10. ^ Fugel, Malte; Malaspina, Lorraine A.; Pal, Rumpa; Thomas, Sajesh P.; Shi, Ming W.; Spackman, Mark A.; Sugimoto, Kunihisa; Grabowsky, Simon (7 May 2019). "Revisiting a Historical Concept by Using Quantum Crystallography: Are Phosphate, Sulfate and Perchlorate Anions Hypervalent?". Chemistry – A European Journal. 25 (26): 6523–6532. doi:10.1002/chem.201806247.
  11. ^ Cundari, Thomas R. (2013). "Chemical bonding involving d-orbitals". Chemical Communications. 49 (83): 9521. doi:10.1039/c3cc45204b.
  12. ^ Magnusson, Eric (October 1990). "Hypercoordinate molecules of second-row elements: d functions or d orbitals?". Journal of the American Chemical Society. 112 (22): 7940–7951. doi:10.1021/ja00178a014.
  13. ^ a b Gamoke, Benjamin; Neff, Diane; Simons, Jack (14 May 2009). "Nature of PO Bonds in Phosphates". The Journal of Physical Chemistry A. 113 (19): 5677–5684. doi:10.1021/jp810014s.
  14. ^ Rajani, Puchakayala; Gopakumar, Gopinadhanpillai; Nagarajan, Sivaraman; Brahmmananda Rao, Cherukuri Venkata Siva (July 2021). "Does the basicity of phosphoryl oxygen change with alkyl chain length in phosphate ligands?". Chemical Physics Letters. 775: 138641. doi:10.1016/j.cplett.2021.138641.
  15. ^ Chesnut, D. B. (1 May 2003). "Atoms-in-Molecules and Electron Localization Function Study of the Phosphoryl Bond". The Journal of Physical Chemistry A. 107 (21): 4307–4313. doi:10.1021/jp022292r.
  16. ^ Corbridge, Derek E. C. (1971). "The structural chemistry of phosphates". Bulletin de la Société française de Minéralogie et de Cristallographie. 94 (3): 271–299. doi:10.3406/bulmi.1971.6534.
  17. ^ Rai, Uma S.; Symons, Martyn C. R. (1994). "EPR data do not support the P=O representation for trialkyl phosphates and phosphine oxides or sulfides". J. Chem. Soc., Faraday Trans. 90 (18): 2649–2652. doi:10.1039/FT9949002649.
  18. ^ Kumler, W. D.; Eiler, John J. (December 1943). "The Acid Strength of Mono and Diesters of Phosphoric Acid. The n-Alkyl Esters from Methyl to Butyl, the Esters of Biological Importance, and the Natural Guanidine Phosphoric Acids". Journal of the American Chemical Society. 65 (12): 2355–2361. doi:10.1021/ja01252a028.
  19. ^ Möller, A.; Sturm, R.; Xie, Z.; Cai, M.; He, J.; Ebinghaus, R. (2012). "Organophosphorus Flame Retardants and Plasticizers in Airborne Particles over the Northern Pacific and Indian Ocean toward the Polar Regions: Evidence for Global Occurrence". Environmental Science and Technology. 46 (6): 3127–3134. Bibcode:2012EnST...46.3127M. doi:10.1021/es204272v. PMID 22332897.
  20. ^ a b c Greaves, Alana K.; Letcher, Robert J. (January 2017). "A Review of Organophosphate Esters in the Environment from Biological Effects to Distribution and Fate". Bulletin of Environmental Contamination and Toxicology. 98 (1): 2–7. doi:10.1007/s00128-016-1898-0.
  21. ^ McDonough, Carrie A.; De Silva, Amila O.; Sun, Caoxin; Cabrerizo, Ana; Adelman, David; Soltwedel, Thomas; Bauerfeind, Eduard; Muir, Derek C. G.; Lohmann, Rainer (2018-06-05). "Dissolved Organophosphate Esters and Polybrominated Diphenyl Ethers in Remote Marine Environments: Arctic Surface Water Distributions and Net Transport through Fram Strait". Environmental Science & Technology. 52 (11): 6208–6216. Bibcode:2018EnST...52.6208M. doi:10.1021/acs.est.8b01127. ISSN 0013-936X. PMID 29787253.
  22. ^ "Status and Trends of Pesticide Use". United Nations Environment Programme. World Health Organization, & Food and Agriculture Organization of the United Nations. 2022.
  23. ^ a b Costa, Lucio G (1 March 2018). "Organophosphorus Compounds at 80: Some Old and New Issues". Toxicological Sciences. 162 (1): 24–35. doi:10.1093/toxsci/kfx266.
  24. ^ Ritter SK (2009). "Pinpointing Trends In Pesticide Use. Limited data indicate that pesticide use has dropped since the 1970s". Chemical & Engineering News. Vol. 87, no. 7. ACS. ISSN 0009-2347.
  25. ^ Costa, Lucio G. (1987). "Toxicology of Pesticides: A Brief History". Toxicology of Pesticides: 1–10. doi:10.1007/978-3-642-70898-5_1.
  26. ^ Richmond, Martha (2021). "Discovery and Commercial Introduction and Mode of Action of Parathion, Malathion, Diazinon, Tetrachlorvinphos, and Glyphosate". Cancer Hazards: Parathion, Malathion, Diazinon, Tetrachlorvinphos and Glyphosate: 3–11. doi:10.1007/978-3-030-81953-8_1.
  27. ^ Peter, J. V.; Sudarsan, T. I.; Moran, J. L. (2014). "Clinical features of organophosphate poisoning: A review of different classification systems and approaches". Indian Journal of Critical Care Medicine. 18 (11): 735–745. doi:10.4103/0972-5229.144017. PMC 4238091. PMID 25425841.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  28. ^ O’Brien, R. D.; Thorn, G. D.; Fisher, R. W. (1 October 1958). "New Organophosphate Insecticides Developed on Rational Principles1". Journal of Economic Entomology. 51 (5): 714–718. doi:10.1093/jee/51.5.714.
  29. ^ Salgado, Vincent L; David, Michael D (April 2017). "Chance and design in proinsecticide discovery". Pest Management Science. 73 (4): 723–730. doi:10.1002/ps.4502.
  30. ^ Gage, J. C. (1 June 1953). "A cholinesterase inhibitor derived from OO -diethyl O - p -nitrophenyl thiophosphate in vivo". Biochemical Journal. 54 (3): 426–430. doi:10.1042/bj0540426.
  31. ^ "The decomposition of some organophosphorus insecticides and related compounds in plants". Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences. 239 (663): 191–214. 22 December 1955. doi:10.1098/rstb.1955.0009.
  32. ^ Spencer, E. Y.; O'Brien, R. D.; White, R. W. (February 1957). "Metabolism of Insecticides, Permanganate Oxidation Products of Schradan". Journal of Agricultural and Food Chemistry. 5 (2): 123–127. doi:10.1021/jf60072a004.
  33. ^ Davison, A. N. (1 June 1955). "Return of cholinesterase activity in the rat after inhibition by organophosphorus compounds. 2. A comparative study of true and pseudo cholinesterase". Biochemical Journal. 60 (2): 339–346. doi:10.1042/bj0600339.
  34. ^ Metcalf, Robert L.; March, Ralph B. (1 March 1953). "Further Studies1 on the Mode of Action of Organic Thionophosphate Insecticides". Annals of the Entomological Society of America. 46 (1): 63–74. doi:10.1093/aesa/46.1.63.
  35. ^ Spencer, E. Y.; O'Brien, R. D. (August 1953). "Schradan, Enhancement of Anticholinesterase Activity in Octamethylpyrophosphoramide by Chlorine". Journal of Agricultural and Food Chemistry. 1 (11): 716–720. doi:10.1021/jf60011a003.
  36. ^ O'Brien, R. D. (1 May 1961). "The effect of SKF 525A (2-diethylaminoethyl 2:2-diphenylvalerate hydrochloride) on organophosphate metabolism in insects and mammals". Biochemical Journal. 79 (2): 229–235. doi:10.1042/bj0790229.
  37. ^ Mew, Emma J.; Padmanathan, Prianka; Konradsen, Flemming; Eddleston, Michael; Chang, Shu-Sen; Phillips, Michael R.; Gunnell, David (September 2017). "The global burden of fatal self-poisoning with pesticides 2006-15: Systematic review". Journal of Affective Disorders. 219: 93–104. doi:10.1016/j.jad.2017.05.002.
  38. ^ Jokanović, Milan; Oleksak, Patrik; Kuca, Kamil (January 2023). "Multiple neurological effects associated with exposure to organophosphorus pesticides in man". Toxicology. 484: 153407. doi:10.1016/j.tox.2022.153407.
  39. ^ "The environmental, human health and economic impacts of pesticides" (PDF). United Nations Environment Programme [UNEP]. Retrieved 2 January 2024.
  40. ^ "Some Organophosphate Insecticides and Herbicides". IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. 12. International Agency for Research on Cancer: 464. 2017. PMID 31829533.
  41. ^ Muñoz-Quezada, María Teresa; Lucero, Boris A.; Barr, Dana B.; Steenland, Kyle; Levy, Karen; Ryan, P. Barry; Iglesias, Veronica; Alvarado, Sergio; Concha, Carlos; Rojas, Evelyn; Vega, Catalina (December 2013). "Neurodevelopmental effects in children associated with exposure to organophosphate pesticides: A systematic review". NeuroToxicology. 39: 158–168. doi:10.1016/j.neuro.2013.09.003.
  42. ^ Muñoz-Quezada, María Teresa; Lucero, Boris Andrés; Iglesias, Verónica Paz; Muñoz, María Pía; Cornejo, Claudia Alejandra; Achu, Eduardo; Baumert, Brittney; Hanchey, Arianna; Concha, Carlos; Brito, Ana María; Villalobos, Marcos (2 January 2016). "Chronic exposure to organophosphate (OP) pesticides and neuropsychological functioning in farm workers: a review". International Journal of Occupational and Environmental Health. 22 (1): 68–79. doi:10.1080/10773525.2015.1123848.
  43. ^ "Status and Trends of Pesticide Use". United Nations Environment Programme. World Health Organization, & Food and Agriculture Organization of the United Nations. 2022.
  44. ^ Clune, Alison L.; Ryan, P. Barry; Barr, Dana Boyd (April 2012). "Have Regulatory Efforts to Reduce Organophosphorus Insecticide Exposures Been Effective?". Environmental Health Perspectives. 120 (4): 521–525. doi:10.1289/ehp.1104323.
  45. ^ Stone, David L; Sudakin, Daniel L; Jenkins, Jeffrey J (December 2009). "Longitudinal trends in organophosphate incidents reported to the National Pesticide Information Center, 1995–2007". Environmental Health. 8 (1). doi:10.1186/1476-069X-8-18.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  46. ^ Souza, Marília Cristina Oliveira; Cruz, Jonas Carneiro; Cesila, Cibele Aparecida; Gonzalez, Neus; Rocha, Bruno Alves; Adeyemi, Joseph A.; Nadal, Marti; Domingo, José L.; Barbosa, Fernando (July 2023). "Recent trends in pesticides in crops: A critical review of the duality of risks-benefits and the Brazilian legislation issue". Environmental Research. 228: 115811. doi:10.1016/j.envres.2023.115811.
  47. ^ Galt, Ryan E. (October 2008). "Beyond the circle of poison: Significant shifts in the global pesticide complex, 1976–2008" (PDF). Global Environmental Change. 18 (4): 786–799. doi:10.1016/j.gloenvcha.2008.07.003.
  48. ^ Maggi, Federico; Tang, Fiona H. M.; la Cecilia, Daniele; McBratney, Alexander (12 September 2019). "PEST-CHEMGRIDS, global gridded maps of the top 20 crop-specific pesticide application rates from 2015 to 2025". Scientific Data. 6 (1). doi:10.1038/s41597-019-0169-4.
  49. ^ "Tolerance Revocations: Chlorpyrifos". www.regulations.gov. Retrieved 2 January 2024. Federal Register Number: 2021-18091
  50. ^ Umetsu, Noriharu; Shirai, Yuichi (20 May 2020). "Development of novel pesticides in the 21st century". Journal of Pesticide Science. 45 (2): 54–74. doi:10.1584/jpestics.D20-201.
  51. ^ Gray, George M.; Hammitt, James K. (October 2000). "Risk/Risk Trade‐offs in Pesticide Regulation: An Exploratory Analysis of the Public Health Effects of a Ban on Organophosphate and Carbamate Pesticides". Risk Analysis. 20 (5): 665–680. doi:10.1111/0272-4332.205060.
  52. ^ Siegfried, Blair D.; Scharf, Michael E. (2001). "Mechanisms of Organophosphate Resistance in Insects". Biochemical Sites of Insecticide Action and Resistance: 269–291. doi:10.1007/978-3-642-59549-3_13.
  53. ^ a b van der Veen, Ike; de Boer, Jacob (August 2012). "Phosphorus flame retardants: Properties, production, environmental occurrence, toxicity and analysis". Chemosphere. 88 (10): 1119–1153. doi:10.1016/j.chemosphere.2012.03.067.
  54. ^ Schmitt, Elmar (May 2007). "Phosphorus-based flame retardants for thermoplastics". Plastics, Additives and Compounding. 9 (3): 26–30. doi:10.1016/S1464-391X(07)70067-3.
  55. ^ He, Huan; Gao, Zhanqi; Zhu, Donglin; Guo, Jiehong; Yang, Shaogui; Li, Shiyin; Zhang, Limin; Sun, Cheng (December 2017). "Assessing bioaccessibility and bioavailability of chlorinated organophosphorus flame retardants in sediments". Chemosphere. 189: 239–246. doi:10.1016/j.chemosphere.2017.09.017.
  56. ^ Blum, Arlene; Behl, Mamta; Birnbaum, Linda S.; Diamond, Miriam L.; Phillips, Allison; Singla, Veena; Sipes, Nisha S.; Stapleton, Heather M.; Venier, Marta (12 November 2019). "Organophosphate Ester Flame Retardants: Are They a Regrettable Substitution for Polybrominated Diphenyl Ethers?". Environmental Science & Technology Letters. 6 (11): 638–649. doi:10.1021/acs.estlett.9b00582.
  57. ^ Du, Jia; Li, Huanxuan; Xu, Shaodan; Zhou, Qingwei; Jin, Meiqing; Tang, Junhong (August 2019). "A review of organophosphorus flame retardants (OPFRs): occurrence, bioaccumulation, toxicity, and organism exposure". Environmental Science and Pollution Research. 26 (22): 22126–22136. doi:10.1007/s11356-019-05669-y.
  58. ^ "ECHA identifies certain brominated flame retardants as candidates for restriction". echa.europa.eu. European Chemicals Agency. Retrieved 3 January 2024.
  59. ^ a b "Regulatory strategy for flame retardant". European Chemicals Agency. Retrieved 3 January 2024.doi:10.2823/854233
  60. ^ Weil, E.D.; Levchik, S.V. (26 January 2001). "Phosphorus Flame Retardants". Kirk-Othmer Encyclopedia of Chemical Technology. doi:10.1002/0471238961.1608151923050912.a01.pub3.
  61. ^ Pawlowski, Kristin H; Schartel, Bernhard (November 2007). "Flame retardancy mechanisms of triphenyl phosphate, resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate) in polycarbonate/acrylonitrile–butadiene–styrene blends". Polymer International. 56 (11): 1404–1414. doi:10.1002/pi.2290.
  62. ^ Blum, Arlene; Behl, Mamta; Birnbaum, Linda S.; Diamond, Miriam L.; Phillips, Allison; Singla, Veena; Sipes, Nisha S.; Stapleton, Heather M.; Venier, Marta (12 November 2019). "Organophosphate Ester Flame Retardants: Are They a Regrettable Substitution for Polybrominated Diphenyl Ethers?". Environmental Science & Technology Letters. 6 (11): 638–649. doi:10.1021/acs.estlett.9b00582.
  63. ^ Du, Jia; Li, Huanxuan; Xu, Shaodan; Zhou, Qingwei; Jin, Meiqing; Tang, Junhong (August 2019). "A review of organophosphorus flame retardants (OPFRs): occurrence, bioaccumulation, toxicity, and organism exposure". Environmental Science and Pollution Research. 26 (22): 22126–22136. doi:10.1007/s11356-019-05669-y.
  64. ^ Barth, Mary L.; Craig, Peter H. (October 1999). "Evaluation of the hazards of industrial exposure to tricresyl phosphate:a review and interpretation of the literature". Journal of Toxicology and Environmental Health, Part B. 2 (4): 281–300. doi:10.1080/109374099281142.
  65. ^ Truong, Jimmy W.; Diamond, Miriam L.; Helm, Paul A.; Jantunen, Liisa M. (December 2017). "Isomers of tris(chloropropyl) phosphate (TCPP) in technical mixtures and environmental samples". Analytical and Bioanalytical Chemistry. 409 (30): 6989–6997. doi:10.1007/s00216-017-0572-7.
  66. ^ Amiri, Roshanak; Bissram, Meera J.; Hashemihedeshi, Mahin; Dorman, Frank L.; Megson, David; Jobst, Karl J. (5 April 2023). "Differentiating Toxic and Nontoxic Tricresyl Phosphate Isomers Using Ion–Molecule Reactions with Oxygen". Journal of the American Society for Mass Spectrometry. 34 (4): 640–648. doi:10.1021/jasms.2c00334.
  67. ^ Duarte, Daniel J.; Rutten, Joost M.M.; van den Berg, Martin; Westerink, Remco H.S. (March 2017). "In vitro neurotoxic hazard characterization of different tricresyl phosphate (TCP) isomers and mixtures". NeuroToxicology. 59: 222–230. doi:10.1016/j.neuro.2016.02.001.
  68. ^ a b Cadogan DF, Howick CJ (15 June 2000). "Plasticizers". Ullmann's Encyclopedia of Industrial Chemistry. 27: 613–614. doi:10.1002/14356007.a20_439. ISBN 3527306730.
  69. ^ Rahman, M; Brazel, C (December 2004). "The plasticizer market: an assessment of traditional plasticizers and research trends to meet new challenges". Progress in Polymer Science. 29 (12): 1223–1248. doi:10.1016/j.progpolymsci.2004.10.001.
  70. ^ Krauskopf LG (2009). "3.13 Plasticizers". Plastics additives handbook (6. ed.). Munich: Carl Hanser Verlag. pp. 485–511. ISBN 978-3-446-40801-2.
  71. ^ William Coaker, A. (September 2003). "Fire and flame retardants for PVC". Journal of Vinyl and Additive Technology. 9 (3): 108–115. doi:10.1002/vnl.10072.
  72. ^ Grossman, Richard F (2008-05-02). Handbook of Vinyl Formulating. John Wiley & Sons. p. 289. ISBN 978-0-470-25354-0.
  73. ^ Levchik, Sergei V.; Weil, Edward D. (October 2005). "Overview of the recent literature on flame retardancy and smoke suppression in PVC". Polymers for Advanced Technologies. 16 (10): 707–716. doi:10.1002/pat.645.
  74. ^ Rudnick, L.R. (2013). "Chapter 4: Neutral Phosphate Esters". Synthetics, Mineral Oils, and Bio-Based Lubricants: Chemistry and Technology, Second Edition. Chemical Industries. CRC Press. pp. 81–104. doi:10.1201/9781315158150-4. ISBN 978-1-4398-5538-6. Retrieved 2024-01-07.
  75. ^ Guan, Bihan; Pochopien, Bernadeta A.; Wright, Dominic S. (August 2016). "The chemistry, mechanism and function of tricresyl phosphate (TCP) as an anti‐wear lubricant additive". Lubrication Science. 28 (5): 257–265. doi:10.1002/ls.1327.
  76. ^ Johnson, David; Hils, John (18 December 2013). "Phosphate Esters, Thiophosphate Esters and Metal Thiophosphates as Lubricant Additives". Lubricants. 1 (4): 132–148. doi:10.3390/lubricants1040132.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  77. ^ Li, Haogang; Zhang, Yanbin; Li, Changhe; Zhou, Zongming; Nie, Xiaolin; Chen, Yun; Cao, Huajun; Liu, Bo; Zhang, Naiqing; Said, Zafar; Debnath, Sujan; Jamil, Muhammad; Ali, Hafiz Muhammad; Sharma, Shubham (May 2022). "Extreme pressure and antiwear additives for lubricant: academic insights and perspectives". The International Journal of Advanced Manufacturing Technology. 120 (1–2): 1–27. doi:10.1007/s00170-021-08614-x.
  78. ^ Hidayah, Nur Nadiatul; Abidin, Sumaiya Zainal (June 2018). "The evolution of mineral processing in extraction of rare earth elements using liquid-liquid extraction: A review". Minerals Engineering. 121: 146–157. doi:10.1016/j.mineng.2018.03.018.
  79. ^ Xie, Feng; Zhang, Ting An; Dreisinger, David; Doyle, Fiona (February 2014). "A critical review on solvent extraction of rare earths from aqueous solutions". Minerals Engineering. 56: 10–28. doi:10.1016/j.mineng.2013.10.021.
  80. ^ Paiva, A. P.; Malik, P. (2004). "Recent advances on the chemistry of solvent extraction applied to the reprocessing of spent nuclear fuels and radioactive wastes". Journal of Radioanalytical and Nuclear Chemistry. 261 (2): 485–496. doi:10.1023/B:JRNC.0000034890.23325.b5. S2CID 94173845.
  81. ^ a b Farn, R.J. (2008). Chemistry and Technology of Surfactants. Wiley. pp. 122–124. ISBN 978-1-4051-7179-3. Retrieved 2023-05-27.
  82. ^ Arora, Pinklesh; Singh, Rakhi; Seshadri, Geetha; Tyagi, Ajay Kumar (16 July 2018). "Synthesis, Properties and Applications of Anionic Phosphate Ester Surfactants: A Review". Tenside Surfactants Detergents. 55 (4): 266–272. doi:10.3139/113.110570.
  83. ^ Kaneko, T.M.; Spicer, L.D. (1985). Pesticide Formulations and Application Systems: Fourth Symposium : a Symposium Sponsored by ASTM Committee E-35 on Pesticides, New Orleans, La., 2-3 Nov. 1983. ASTM special technical publication. ASTM. pp. 5–14. ISBN 978-0-8031-0413-6. Retrieved 2023-05-27.
  84. ^ Miller, Dennis; Wiener, Eva-Maria; Turowski, Angelika; Thunig, Christine; Hoffmann, Heinz (July 1999). "O/W emulsions for cosmetics products stabilized by alkyl phosphates — rheology and storage tests". Colloids and Surfaces A: Physicochemical and Engineering Aspects. 152 (1–2): 155–160. doi:10.1016/S0927-7757(98)00630-X.
  85. ^ Petroianu, G. A. (2010-10-01). "Toxicity of phosphor esters: Willy Lange (1900-1976) and Gerda von Krueger (1907-after 1970)". Die Pharmazie. 65 (10): 776–780. ISSN 0031-7144. PMID 21105582.
  86. ^ Chai, Peter R.; Hayes, Bryan D.; Erickson, Timothy B.; Boyer, Edward W. (January 2018). "Novichok agents: a historical, current, and toxicological perspective". Toxicology Communications. 2 (1): 45–48. doi:10.1080/24734306.2018.1475151. PMC 6039123. PMID 30003185. S2CID 49661943.
  87. ^ Vale, J. Allister; Marrs, Timothy C.; Maynard, Robert L. (2 November 2018). "Novichok: a murderous nerve agent attack in the UK". Clinical Toxicology. 56 (11): 1093–1097. doi:10.1080/15563650.2018.1469759.
  88. ^ Salamova, Amina; Ma, Yuning; Venier, Marta; Hites, Ronald A. (2014-01-14). "High Levels of Organophosphate Flame Retardants in the Great Lakes Atmosphere". Environmental Science & Technology Letters. 1 (1): 8–14. doi:10.1021/ez400034n.
  89. ^ a b Venier, Marta; Dove, Alice; Romanak, Kevin; Backus, Sean; Hites, Ronald (2014-08-19). "Flame Retardants and Legacy Chemicals in Great Lakes' Water". Environmental Science & Technology. 48 (16): 9563–9572. Bibcode:2014EnST...48.9563V. doi:10.1021/es501509r. ISSN 0013-936X. PMID 25045802.