Pyrethroid - Revision history

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	Pyrethroids are toxic to insects such as [[bee]]s, [[dragonflies]], [[mayflies]], [[Horse-fly\|gadflies]], and some other [[invertebrates]], including those that constitute the base of aquatic and terrestrial [[food webs]].<ref name=dc/> They are toxic to aquatic organisms including fish.<ref name=idph/>		Pyrethroids are toxic to insects such as [[bee]]s, [[dragonflies]], [[mayflies]], [[Horse-fly\|gadflies]], and some other [[invertebrates]], including those that constitute the base of aquatic and terrestrial [[food webs]].<ref name=dc/> They are toxic to aquatic organisms including fish.<ref name=idph/>

	Pyrethroids are usually [[Chemical decomposition\|broken apart]] by [[sunlight]] and the atmosphere in one or two days, however when associated with sediment they can persist for some time.{{better reference\|date=October 2024}}<ref>{{cite journal \|doi=10.1371/journal.pone.0015794 \|pmid=21246035 \|pmc=3016336 \|title=Environmental Modeling and Exposure Assessment of Sediment-Associated Pyrethroids in an Agricultural Watershed \|journal=[[PLOS ONE]]\|volume=6 \|issue=1 \|~~pages~~=e15794 \|year=2011 \|last1=Luo \|first1=Yuzhou \|last2=Zhang \|first2=Minghua \|bibcode=2011PLoSO...615794L \|doi-access=free }}</ref>		Pyrethroids are usually [[Chemical decomposition\|broken apart]] by [[sunlight]] and the atmosphere in one or two days, however when associated with sediment they can persist for some time.{{better reference\|date=October 2024}}<ref>{{cite journal \|doi=10.1371/journal.pone.0015794 \|pmid=21246035 \|pmc=3016336 \|title=Environmental Modeling and Exposure Assessment of Sediment-Associated Pyrethroids in an Agricultural Watershed \|journal=[[PLOS ONE]]\|volume=6 \|issue=1 \|article-number=e15794 \|year=2011 \|last1=Luo \|first1=Yuzhou \|last2=Zhang \|first2=Minghua \|bibcode=2011PLoSO...615794L \|doi-access=free }}</ref>

	Pyrethroids are unaffected by conventional secondary treatment systems at municipal [[wastewater treatment]] facilities. They appear in the effluent, usually at levels lethal to invertebrates.{{better reference\|date=October 2024}}<ref name="weston">{{cite journal \|doi=10.1021/es9035573 \|pmid=20121184 \|title=Urban and Agricultural Sources of Pyrethroid Insecticides to the Sacramento-San Joaquin Delta of California \|journal= [[Environmental Science & Technology]] \|volume=44 \|issue=5 \|pages=1833–40 \|year=2010 \|last1=Weston \|first1=Donald P \|last2=Lydy \|first2=Michael J \|bibcode=2010EnST...44.1833W }}</ref>		Pyrethroids are unaffected by conventional secondary treatment systems at municipal [[wastewater treatment]] facilities. They appear in the effluent, usually at levels lethal to invertebrates.{{better reference\|date=October 2024}}<ref name="weston">{{cite journal \|doi=10.1021/es9035573 \|pmid=20121184 \|title=Urban and Agricultural Sources of Pyrethroid Insecticides to the Sacramento-San Joaquin Delta of California \|journal= [[Environmental Science & Technology]] \|volume=44 \|issue=5 \|pages=1833–40 \|year=2010 \|last1=Weston \|first1=Donald P \|last2=Lydy \|first2=Michael J \|bibcode=2010EnST...44.1833W }}</ref>

	===Humans===		===Humans===
	Pyrethroid absorption can happen via skin, inhalation or ingestion.<ref name=":0">{{Cite journal\|last1=Bradberry\|first1=Sally M.\|last2=Cage\|first2=Sarah A.\|last3=Proudfoot\|first3=Alex T.\|last4=Vale\|first4=J. Allister\|date=2005\|title=Poisoning due to pyrethroids\|journal=[[Toxicological Reviews]]\|volume=24\|issue=2\|pages=93–106\|doi=10.2165/00139709-200524020-00003\|issn=1176-2551\|pmid=16180929\|s2cid=32523158}}</ref> Pyrethroids often do not bind efficiently to mammalian [[sodium channel]]s.<ref>{{Cite journal\|display-authors=etal\|vauthors=Silver KS\|date=2014\|title=Voltage-gated sodium channels as insecticide targets\|journal=[[Advances in Insect Physiology]]\|volume=46\|pages=389–433\|doi=10.1016/B978-0-12-417010-0.00005-7\|pmc=6005695\|pmid=29928068\|isbn=~~9780124170100~~}}</ref> They also absorb poorly via skin and human liver is often able to metabolize them relatively efficiently. Pyrethroids are thus much less toxic to humans than to insects.<ref>{{Cite journal\|last1=Ray\|first1=David E.\|last2=Ray\|first2=Dr David\|last3=Forshaw\|first3=Philip J.\|date=2000-01-01\|title=Pyrethroid Insecticides: Poisoning Syndromes, Synergies, and Therapy\|journal=[[Journal of Toxicology: Clinical Toxicology]]\|volume=38\|issue=2\|pages=95–101\|doi=10.1081/CLT-100100922\|issn=0731-3810\|pmid=10778904\|s2cid=22213256}}</ref>		Pyrethroid absorption can happen via skin, inhalation or ingestion.<ref name=":0">{{Cite journal\|last1=Bradberry\|first1=Sally M.\|last2=Cage\|first2=Sarah A.\|last3=Proudfoot\|first3=Alex T.\|last4=Vale\|first4=J. Allister\|date=2005\|title=Poisoning due to pyrethroids\|journal=[[Toxicological Reviews]]\|volume=24\|issue=2\|pages=93–106\|doi=10.2165/00139709-200524020-00003\|issn=1176-2551\|pmid=16180929\|s2cid=32523158}}</ref> Pyrethroids often do not bind efficiently to mammalian [[sodium channel]]s.<ref>{{Cite journal\|display-authors=etal\|vauthors=Silver KS\|date=2014\|title=Voltage-gated sodium channels as insecticide targets\|journal=[[Advances in Insect Physiology]]\|volume=46\|pages=389–433\|doi=10.1016/B978-0-12-417010-0.00005-7\|pmc=6005695\|pmid=29928068\|isbn=978-0-12-417010-0}}</ref> They also absorb poorly via skin and human liver is often able to metabolize them relatively efficiently. Pyrethroids are thus much less toxic to humans without liver problems than to insects.<ref>{{Cite journal\|last1=Ray\|first1=David E.\|last2=Ray\|first2=Dr David\|last3=Forshaw\|first3=Philip J.\|date=2000-01-01\|title=Pyrethroid Insecticides: Poisoning Syndromes, Synergies, and Therapy\|journal=[[Journal of Toxicology: Clinical Toxicology]]\|volume=38\|issue=2\|pages=95–101\|doi=10.1081/CLT-100100922\|issn=0731-3810\|pmid=10778904\|s2cid=22213256}}</ref>

	It is not well established if chronic exposure to small amounts of pyrethroids is hazardous or not.<ref>{{Cite journal\|last1=Burns\|first1=C\|last2=Pastoor\|first2=T\|date=2018\|title=Pyrethroid epidemiology: a quality-based review\|journal=[[Critical Reviews in Toxicology]]\|volume=48\|issue=4\|pages=297–311\|doi=10.1080/10408444.2017.1423463\|pmid=29389244\|doi-access=free}}</ref> However, large doses can cause acute poisoning, which is rarely life threatening. Typical symptoms include facial [[paresthesia]], itching, burning, dizziness, nausea, vomiting and more severe cases of muscle twitching. Severe poisoning is often caused by ingestion of pyrethroids and can result in a variety of symptoms like seizures, [[coma]], bleeding or [[pulmonary edema]].<ref name=":0" /> There is an association of pyrethroids with poorer early social-emotional and language development.<ref name=VHEMBE />		It is not well established if chronic exposure to small amounts of pyrethroids is hazardous or not.<ref>{{Cite journal\|last1=Burns\|first1=C\|last2=Pastoor\|first2=T\|date=2018\|title=Pyrethroid epidemiology: a quality-based review\|journal=[[Critical Reviews in Toxicology]]\|volume=48\|issue=4\|pages=297–311\|doi=10.1080/10408444.2017.1423463\|pmid=29389244\|doi-access=free}}</ref> However, large doses can cause acute poisoning, which is rarely life threatening. Typical symptoms include facial [[paresthesia]], itching, burning, dizziness, nausea, vomiting and more severe cases of muscle twitching. Severe poisoning is often caused by ingestion of pyrethroids and can result in a variety of symptoms like seizures, [[coma]], bleeding or [[pulmonary edema]].<ref name=":0" /> There is an association of pyrethroids with poorer early social-emotional and language development.<ref name=VHEMBE />
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	The use of pyrethroids as insecticides has led to the development of widespread resistance to them among some insect populations, especially mosquitoes.<ref name="Jeran-et-al-2020">{{cite journal \| last1=Jeran \| first1=Nina \| last2=Grdiša \| first2=Martina \| last3=Varga \| first3=Filip \| last4=Šatović \| first4=Zlatko \| last5=Liber \| first5=Zlatko \| last6=Dabić \| first6=Dario \| last7=Biošić \| first7=Martina \| title=Pyrethrin from Dalmatian pyrethrum (''Tanacetum cinerariifolium''/Trevir./Sch. Bip.): biosynthesis, biological activity, methods of extraction and determination \| journal=[[Phytochemistry Reviews]] \| publisher=[[Springer Science+Business Media]]\| volume=20 \| issue=5 \| date=2020-10-06 \| issn=1568-7767 \| doi=10.1007/s11101-020-09724-2 \| pages=875–905\| s2cid=225152789\|id=[[Phytochemical Society of Europe]]+[[Phytochemical Society of North America]]. MG [[ORCID]]: [http://orcid.org/0000-0002-4584-4851 0000-0002-4584-4851])}}</ref>		The use of pyrethroids as insecticides has led to the development of widespread resistance to them among some insect populations, especially mosquitoes.<ref name="Jeran-et-al-2020">{{cite journal \| last1=Jeran \| first1=Nina \| last2=Grdiša \| first2=Martina \| last3=Varga \| first3=Filip \| last4=Šatović \| first4=Zlatko \| last5=Liber \| first5=Zlatko \| last6=Dabić \| first6=Dario \| last7=Biošić \| first7=Martina \| title=Pyrethrin from Dalmatian pyrethrum (''Tanacetum cinerariifolium''/Trevir./Sch. Bip.): biosynthesis, biological activity, methods of extraction and determination \| journal=[[Phytochemistry Reviews]] \| publisher=[[Springer Science+Business Media]]\| volume=20 \| issue=5 \| date=2020-10-06 \| issn=1568-7767 \| doi=10.1007/s11101-020-09724-2 \| pages=875–905\| s2cid=225152789\|id=[[Phytochemical Society of Europe]]+[[Phytochemical Society of North America]]. MG [[ORCID]]: [http://orcid.org/0000-0002-4584-4851 0000-0002-4584-4851])}}</ref>

	Pyrethroids have been used against bedbugs, but resistant populations have developed to them.<ref name="JAMA2009">{{cite journal \|doi=10.1001/jama.2009.405 \|pmid=19336711 \|title=Bed Bugs ''Cimex lectularius'' and Clinical Consequences of Their Bites \|journal=[[JAMA]]\|volume=301 \|issue=13 \|pages=1358–66 \|year=2009 \|last1=Goddard \|first1=Jerome \|last2=Deshazo \|first2=R \|doi-access= }}</ref><ref name="Kolb2009">{{cite journal \|doi=10.1111/j.1529-8019.2009.01246.x \|pmid=19580578 \|title=Bedbugs \|journal=[[Dermatologic Therapy]]\|volume=22 \|issue=4 \|pages=347–52 \|year=2009 \|last1=Kolb \|first1=Adam \|last2=Needham \|first2=Glen R \|last3=Neyman \|first3=Kimberly M \|last4=High \|first4=Whitney A \|s2cid=221648188 \|doi-access=free }}</ref><ref name="voiland">Voiland, Adam. [http://health.usnews.com/usnews/health/articles/070708/16bedbug.htm "You May not be Alone"] {{webarchive\|url=https://web.archive.org/web/20111107010535/http://health.usnews.com/usnews/health/articles/070708/16bedbug.htm \|date=2011-11-07 }} U.S. News & World Report 16 July 2007, Vol. 143, Issue 2, p53–54.</ref><ref>{{cite journal \|doi=10.1603/0022-2585(2008)45[1092:BAMAOD]2.0.CO;2 \|pmid=19058634 \|year=2008 \|volume=45 \|issue=6 \|pages=1092–101 \|title=Biochemical and Molecular Analysis of Deltamethrin Resistance in the Common Bed Bug (Hemiptera: Cimicidae) \|journal=[[Journal of Medical Entomology]]\|last1=Yoon \|first1=Kyong Sup \|last2=Kwon \|first2=Deok Ho \|last3=Strycharz \|first3=Joseph P \|last4=Hollingsworth \|first4=Craig S \|last5=Lee \|first5=Si Hyeock \|last6=Clark \|first6=J. Marshall \|doi-broken-date=~~16 January~~ 2025 \|s2cid=27422270 }}</ref> Populations of [[diamondback moth]]s have also commonly developed resistance to pyrethroids<ref>{{cite journal\|last1=Leibee\|first1=Gary L.\|last2=Savage\|first2=Kenneth E.\|year=1992\|title=Evaluation of Selected Insecticides for Control of Diamondback Moth and Cabbage Looper in Cabbage in Central Florida with Observations on Insecticide Resistance in the Diamondback Moth\|journal=The Florida Entomologist\|volume=75\|issue=4\|~~pages~~=585\|doi=10.2307/3496140\|issn=0015-4040\|jstor=3496140}}</ref>{{better source needed\|date=January 2022}} {{endash}} including in U.S. states [[North Dakota]]<ref name="NDSUExt">{{cite web \| title=Pyrethroid Complaints for Diamondback Moth Control in Canola (08/26/21) \| website=[[NDSU Extension\|NDSU Agriculture and Extension]] \| date=2021-08-26 \| url=http://www.ag.ndsu.edu:8000/agriculture/ag-hub/ag-topics/crop-production/crop-pest-report/entomology/pyrethroid-complaints-diamondback-moth \| access-date=2022-01-08 }}{{Dead link\|date=December 2024 \|bot=InternetArchiveBot \|fix-attempted=yes }}</ref> and [[Wisconsin]]<ref name="WiscHortDBM">{{cite web \| last=Marsden \| first=Christy \| title=Diamondback Moth \| website=[[Wisconsin Horticulture]] \| date=2021-10-15 \| url=http://hort.extension.wisc.edu/articles/diamondback-moth/ \| access-date=2022-01-08}}</ref> while pyrethroids are still recommended in [[California]].<ref name="UCANRDBM">{{cite web \| url=http://www2.ipm.ucanr.edu/agriculture/floriculture-and-ornamental-nurseries/Diamondback-moth/ \| title=Diamondback Moth - Floriculture and Ornamental Nurseries Pest Management Guidelines \| website=[[University of California Agriculture and Natural Resources]] (UCANR)}}</ref> Various mosquito populations have been discovered to have a high level of resistance, including ''[[Anopheles gambiae sensu lato\|Anopheles gambiae s.l.]]'' in [[West Africa]] by Chandre et al 1999 through Pwalia et al 2019, ''[[Anopheles arabiensis\|A. arabiensis]]'' in [[Sudan]] by Ismail et al 2018 and [[The Gambia]] by Opondo et al 2019, and ''[[Aedes aegypti]]'' in [[South East Asia]] by Amelia-Yap et al 2018, [[Papua New Guinea]] by Demok et al 2019, and various other locations by Smith et al 2016.<ref name="Jeran-et-al-2020" />		Pyrethroids have been used against bedbugs, but resistant populations have developed to them.<ref name="JAMA2009">{{cite journal \|doi=10.1001/jama.2009.405 \|pmid=19336711 \|title=Bed Bugs ''Cimex lectularius'' and Clinical Consequences of Their Bites \|journal=[[JAMA]]\|volume=301 \|issue=13 \|pages=1358–66 \|year=2009 \|last1=Goddard \|first1=Jerome \|last2=Deshazo \|first2=R \|doi-access= }}</ref><ref name="Kolb2009">{{cite journal \|doi=10.1111/j.1529-8019.2009.01246.x \|pmid=19580578 \|title=Bedbugs \|journal=[[Dermatologic Therapy]]\|volume=22 \|issue=4 \|pages=347–52 \|year=2009 \|last1=Kolb \|first1=Adam \|last2=Needham \|first2=Glen R \|last3=Neyman \|first3=Kimberly M \|last4=High \|first4=Whitney A \|s2cid=221648188 \|doi-access=free }}</ref><ref name="voiland">Voiland, Adam. [http://health.usnews.com/usnews/health/articles/070708/16bedbug.htm "You May not be Alone"] {{webarchive\|url=https://web.archive.org/web/20111107010535/http://health.usnews.com/usnews/health/articles/070708/16bedbug.htm \|date=2011-11-07 }} U.S. News & World Report 16 July 2007, Vol. 143, Issue 2, p53–54.</ref><ref>{{cite journal \|doi=10.1603/0022-2585(2008)45[1092:BAMAOD]2.0.CO;2 \|pmid=19058634 \|year=2008 \|volume=45 \|issue=6 \|pages=1092–101 \|title=Biochemical and Molecular Analysis of Deltamethrin Resistance in the Common Bed Bug (Hemiptera: Cimicidae) \|journal=[[Journal of Medical Entomology]]\|last1=Yoon \|first1=Kyong Sup \|last2=Kwon \|first2=Deok Ho \|last3=Strycharz \|first3=Joseph P \|last4=Hollingsworth \|first4=Craig S \|last5=Lee \|first5=Si Hyeock \|last6=Clark \|first6=J. Marshall \|doi-broken-date=1 July 2025 \|s2cid=27422270 }}</ref> Populations of [[diamondback moth]]s have also commonly developed resistance to pyrethroids<ref>{{cite journal\|last1=Leibee\|first1=Gary L.\|last2=Savage\|first2=Kenneth E.\|year=1992\|title=Evaluation of Selected Insecticides for Control of Diamondback Moth and Cabbage Looper in Cabbage in Central Florida with Observations on Insecticide Resistance in the Diamondback Moth\|journal=The Florida Entomologist\|volume=75\|issue=4\|page=585\|doi=10.2307/3496140\|issn=0015-4040\|jstor=3496140\|doi-access=free}}</ref>{{better source needed\|date=January 2022}} {{endash}} including in U.S. states [[North Dakota]]<ref name="NDSUExt">{{cite web \| title=Pyrethroid Complaints for Diamondback Moth Control in Canola (08/26/21) \| website=[[NDSU Extension\|NDSU Agriculture and Extension]] \| date=2021-08-26 \| url=http://www.ag.ndsu.edu:8000/agriculture/ag-hub/ag-topics/crop-production/crop-pest-report/entomology/pyrethroid-complaints-diamondback-moth \| access-date=2022-01-08 }}{{Dead link\|date=December 2024 \|bot=InternetArchiveBot \|fix-attempted=yes }}</ref> and [[Wisconsin]]<ref name="WiscHortDBM">{{cite web \| last=Marsden \| first=Christy \| title=Diamondback Moth \| website=[[Wisconsin Horticulture]] \| date=2021-10-15 \| url=http://hort.extension.wisc.edu/articles/diamondback-moth/ \| access-date=2022-01-08}}</ref> while pyrethroids are still recommended in [[California]].<ref name="UCANRDBM">{{cite web \| url=http://www2.ipm.ucanr.edu/agriculture/floriculture-and-ornamental-nurseries/Diamondback-moth/ \| title=Diamondback Moth - Floriculture and Ornamental Nurseries Pest Management Guidelines \| website=[[University of California Agriculture and Natural Resources]] (UCANR)}}</ref> Various mosquito populations have been discovered to have a high level of resistance, including ''[[Anopheles gambiae sensu lato\|Anopheles gambiae s.l.]]'' in [[West Africa]] by Chandre et al 1999 through Pwalia et al 2019, ''[[Anopheles arabiensis\|A. arabiensis]]'' in [[Sudan]] by Ismail et al 2018 and [[The Gambia]] by Opondo et al 2019, and ''[[Aedes aegypti]]'' in [[South East Asia]] by Amelia-Yap et al 2018, [[Papua New Guinea]] by Demok et al 2019, and various other locations by Smith et al 2016.<ref name="Jeran-et-al-2020" />

	{{Vanchor\|[[Knockdown resistance]]\|knockdown resistance\|kdr}} (''kdr'') is one of the stronger kinds of resistance.<ref name="Molecular" /> ''kdr'' [[mutation]]s confer [[target-site resistance]] to [[DDT]] and pyrethroids and [[cross-resistance]] to DDT.<ref name="Molecular" /> Most ''kdr'' mutations are within or proximate to the two arthropod [[sodium channel]] genes.<ref name="Molecular">{{cite journal\|year=2014\|publisher=[[Elsevier BV]]\|pages=1–17\|first8=Boris\|first7=Kristopher\|volume=50\|first6=Lingxin\|first5=Peng\|first4=Yoshiko\|first3=Frank\|first2=Yuzhe\|first1=Ke\|last8=Zhorov\|last7=Silver\|last6=Wang\|last5=Xu\|last4=Nomura\|last3=Rinkevich\|last2=Du\|last1=Dong\|journal=[[Insect Biochemistry and Molecular Biology]]\|issn=0965-1748\|id=[[NIHMSID]]: 582398\|s2cid=6332754\|pmc=4484874\|pmid=24704279\|doi=10.1016/j.ibmb.2014.03.012\|title=Molecular biology of insect sodium channels and pyrethroid resistance\|bibcode=2014IBMB...50....1D }}</ref>		{{Vanchor\|[[Knockdown resistance]]\|knockdown resistance\|kdr}} (''kdr'') is one of the stronger kinds of resistance.<ref name="Molecular" /> ''kdr'' [[mutation]]s confer [[target-site resistance]] to [[DDT]] and pyrethroids and [[cross-resistance]] to DDT.<ref name="Molecular" /> Most ''kdr'' mutations are within or proximate to the two arthropod [[sodium channel]] genes.<ref name="Molecular">{{cite journal\|year=2014\|publisher=[[Elsevier BV]]\|pages=1–17\|first8=Boris\|first7=Kristopher\|volume=50\|first6=Lingxin\|first5=Peng\|first4=Yoshiko\|first3=Frank\|first2=Yuzhe\|first1=Ke\|last8=Zhorov\|last7=Silver\|last6=Wang\|last5=Xu\|last4=Nomura\|last3=Rinkevich\|last2=Du\|last1=Dong\|journal=[[Insect Biochemistry and Molecular Biology]]\|issn=0965-1748\|id=[[NIHMSID]]: 582398\|s2cid=6332754\|pmc=4484874\|pmid=24704279\|doi=10.1016/j.ibmb.2014.03.012\|title=Molecular biology of insect sodium channels and pyrethroid resistance\|bibcode=2014IBMB...50....1D }}</ref>

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{{Short description|Class of insecticides}}
[[File:Allethrin 2D.svg|300px|thumb|Chemical structure of [[Allethrin]] isomers]]
[[File:Permethrin-2D-skeletal.png|300px|thumb|Chemical structure of [[Permethrin]] isomers]]

A '''pyrethroid''' is an [[organic compound]] similar to the natural [[pyrethrin]]s, which are produced by the flowers of [[pyrethrum]]s (''[[Chrysanthemum cinerariaefolium]]'' and ''[[Chrysanthemum coccineum|C. coccineum]]''). Pyrethroids are used as commercial and household [[insecticides]].<ref name="Ullmann" />

In household concentrations pyrethroids are generally harmless to humans.<ref name=Ullmann>{{Ullmann |doi=10.1002/14356007.a14_263 |chapter=Insect Control |year=2000 |last1=Metcalf |first1=Robert L |isbn=3527306730 }}</ref> However, pyrethroids are toxic to insects such as [[bee]]s, [[dragonflies]], [[mayflies]], [[Horse-fly|gadflies]], and some other [[invertebrates]], including those that constitute the base of aquatic and terrestrial [[food webs]].<ref name=dc>{{cite news |url=http://archive.dailycal.org/article/108103/study_links_pesticides_to_river_contamination|title=Study Links Pesticides to River Contamination |last=Zaveri |first=Mihir |date=February 4, 2010|work=The Daily Californian|publisher=The [[Daily Californian]]|access-date=9 June 2012}}</ref> Pyrethroids are toxic to [[aquatic organism]]s, especially fish.<ref name=idph>[http://www.idph.state.il.us/envhealth/factsheets/pyrethroid.htm Pyrethroids fact sheet] from the Illinois Department of Public Health.</ref> They have been shown to be an effective control measure for malaria outbreaks, through indoor applications.<ref name=VHEMBE>{{cite Q|Q52880664}}</ref>

==Mode of action==
Pyrethroids are [[excitotoxin|excitotoxic]] to [[axon]]s. They act by preventing the closure of the [[voltage-gated sodium channel]]s in the axonal [[membrane]]s. The sodium channel is a [[membrane protein]] with a [[hydrophilic]] interior. This interior is shaped precisely to allow [[sodium ion#aqueous solutions|sodium ions]] to pass through the membrane, enter the axon, and propagate an [[action potential]]. When the toxin keeps the channels in their open state, the nerves cannot [[repolarization|repolarize]], leaving the axonal membrane permanently [[depolarization|depolarized]], thereby paralyzing the organism.<ref name=Soderlund>{{cite journal |doi=10.1016/s0300-483x(01)00569-8 |pmid=11812616 |title=Mechanisms of pyrethroid neurotoxicity: Implications for cumulative risk assessment |journal=[[Toxicology (journal)|Toxicology]]|volume=171 |issue=1 |pages=3–59 |year=2002 |last1=Soderlund |first1=David M |last2=Clark |first2=John M |last3=Sheets |first3=Larry P |last4=Mullin |first4=Linda S |last5=Piccirillo |first5=Vincent J |last6=Sargent |first6=Dana |last7=Stevens |first7=James T |last8=Weiner |first8=Myra L |bibcode=2002Toxgy.171....3S }}</ref> Pyrethroids can be combined with the synergist [[piperonyl butoxide]], a known [[enzyme inhibitor|inhibitor]] of [[microsomal P450]] enzymes which are important in metabolizing the pyrethroid. By that means, the efficacy (lethality) of the pyrethroid is increased.<ref name=Denholm>{{cite journal |doi=10.1017/S0007485300054262 |title=An unconventional use of piperonyl butoxide for managing the cotton whitefly, ''Bemisia tabaci'' (Hemiptera: Aleyrodidae) |journal=[[Bulletin of Entomological Research]] |volume=88 |issue=6 |pages=601–10 |year=2009 |last1=Devine |first1=G.J |last2=Denholm |first2=I }}</ref> It is likely that there are other mechanisms of intoxication also.<ref name="Soderlund-Bloomquist-1989" /> Disruption of [[neuroendocrine cell|neuroendocrine]] activity is thought to contribute to their irreversible effects on insects, which indicates a pyrethroid action on [[voltage-gated calcium channel]]s (and perhaps other [[voltage-gated ion channel|voltage-gated channels]] more widely).<ref name="Soderlund-Bloomquist-1989" />

==Chemistry and classification==
[[File:(R,R)-(+)-trans-chrysanthemic acid.svg|thumb|(1''R'',3''R'')- or (+)-trans-[[chrysanthemic acid]].]]
Pyrethroids are classified based on their mechanism of biological action, as they do not share a common chemical structure. Many are 2,2-dimethylcyclopropanecarboxylic acid derivatives, like [[chrysanthemic acid]], [[ester]]ified with an [[Alcohol (chemistry)|alcohol]]. However, the [[cyclopropyl]] ring does not occur in all pyrethroids. [[Fenvalerate]], which was developed in 1972, is one such example and was the first commercialized pyrethroid without that group.

Pyrethroids which lack an α-cyano group are often classified as ''type I pyrethroids'' and those with it are called ''type II pyrethroids''. Pyrethroids that have a common name starting with "cy" have a cyano group and are type II. Fenvalerate also contains an α-[[cyano group]].

Some pyrethroids, like [[etofenprox]], also lack the ester bond found in most other pyrethroids and have an [[ether]] bond in its place. [[Silafluofen]] is also classified as a pyrethroid and has a [[silicon]] atom in the place of the ester. Pyrethroids often have [[chiral centers]] and only certain stereoisomers work efficiently as [[insecticide]]s.<ref>{{Cite journal|last=Ujihara|first=K|date=2019|title=The history of extensive structural modifications of pyrethroids|journal=[[Journal of Pesticide Science]]|volume=44|issue=4|pages=215–224|doi=10.1584/jpestics.D19-102|pmc=6861428|pmid=31777441}}</ref>

==Examples==
{{colbegin}}
*[[Allethrin]], the first pyrethroid synthesized
*[[Bifenthrin]], active ingredient of ''Talstar'', ''Capture'', ''Ortho Home Defense Max'', and ''Bifenthrine''
*[[Cyfluthrin]], an active ingredient in [[Baygon]], Temprid, Fumakilla Vape Aerosol, Tempo SC, and many more, dichlorovinyl derivative of pyrethrin
*[[Cypermethrin]], including the resolved isomer alpha-cypermethrin, dichlorovinyl derivative of pyrethrin. Commonly found in crawling insect killers and some mosquito sprays.
*[[Cyphenothrin]], active ingredient of K2000 Insect spray sold in Israel. Mostly used in some aerosols as a Cypermethrin substitute in developing countries.
*[[Deltamethrin]], dibromovinyl derivative of pyrethrin
*[[Dimefluthrin]]
*[[Esfenvalerate]]
*[[Etofenprox]]
*[[Fenpropathrin]]
*[[Fenvalerate]]
*[[Flucythrinate]]
*[[Flumethrin]]
*[[Imiprothrin]]
*[[lambda-Cyhalothrin]]
*[[Metofluthrin]]
*[[Permethrin]], dichlorovinyl derivative of [[pyrethrin]] and most widely used pyrethroid.
*[[Phenothrin]] (Sumithrin), active ingredient of [[Anvil (insecticide)|Anvil]]
*[[Prallethrin]]
*[[Resmethrin]], active ingredient of ''Scourge''
*[[Silafluofen]]
*[[tau-Fluvalinate]]
*[[Tefluthrin]]
*[[Tetramethrin]]
*[[Tralomethrin]]
*[[Transfluthrin]], an active ingredient in Baygon and other products.
{{colend}}

==Safety==
===Environmental effects===
Pyrethroids are toxic to insects such as [[bee]]s, [[dragonflies]], [[mayflies]], [[Horse-fly|gadflies]], and some other [[invertebrates]], including those that constitute the base of aquatic and terrestrial [[food webs]].<ref name=dc/> They are toxic to aquatic organisms including fish.<ref name=idph/>

Pyrethroids are usually [[Chemical decomposition|broken apart]] by [[sunlight]] and the atmosphere in one or two days, however when associated with sediment they can persist for some time.{{better reference|date=October 2024}}<ref>{{cite journal |doi=10.1371/journal.pone.0015794 |pmid=21246035 |pmc=3016336 |title=Environmental Modeling and Exposure Assessment of Sediment-Associated Pyrethroids in an Agricultural Watershed |journal=[[PLOS ONE]]|volume=6 |issue=1 |pages=e15794 |year=2011 |last1=Luo |first1=Yuzhou |last2=Zhang |first2=Minghua |bibcode=2011PLoSO...615794L |doi-access=free }}</ref>

Pyrethroids are unaffected by conventional secondary treatment systems at municipal [[wastewater treatment]] facilities. They appear in the effluent, usually at levels lethal to invertebrates.{{better reference|date=October 2024}}<ref name="weston">{{cite journal |doi=10.1021/es9035573 |pmid=20121184 |title=Urban and Agricultural Sources of Pyrethroid Insecticides to the Sacramento-San Joaquin Delta of California |journal= [[Environmental Science & Technology]] |volume=44 |issue=5 |pages=1833–40 |year=2010 |last1=Weston |first1=Donald P |last2=Lydy |first2=Michael J |bibcode=2010EnST...44.1833W }}</ref>

===Humans===
Pyrethroid absorption can happen via skin, inhalation or ingestion.<ref name=":0">{{Cite journal|last1=Bradberry|first1=Sally M.|last2=Cage|first2=Sarah A.|last3=Proudfoot|first3=Alex T.|last4=Vale|first4=J. Allister|date=2005|title=Poisoning due to pyrethroids|journal=[[Toxicological Reviews]]|volume=24|issue=2|pages=93–106|doi=10.2165/00139709-200524020-00003|issn=1176-2551|pmid=16180929|s2cid=32523158}}</ref> Pyrethroids often do not bind efficiently to mammalian [[sodium channel]]s.<ref>{{Cite journal|display-authors=etal|vauthors=Silver KS|date=2014|title=Voltage-gated sodium channels as insecticide targets|journal=[[Advances in Insect Physiology]]|volume=46|pages=389–433|doi=10.1016/B978-0-12-417010-0.00005-7|pmc=6005695|pmid=29928068|isbn=9780124170100}}</ref> They also absorb poorly via skin and human liver is often able to metabolize them relatively efficiently. Pyrethroids are thus much less toxic to humans than to insects.<ref>{{Cite journal|last1=Ray|first1=David E.|last2=Ray|first2=Dr David|last3=Forshaw|first3=Philip J.|date=2000-01-01|title=Pyrethroid Insecticides: Poisoning Syndromes, Synergies, and Therapy|journal=[[Journal of Toxicology: Clinical Toxicology]]|volume=38|issue=2|pages=95–101|doi=10.1081/CLT-100100922|issn=0731-3810|pmid=10778904|s2cid=22213256}}</ref>

It is not well established if chronic exposure to small amounts of pyrethroids is hazardous or not.<ref>{{Cite journal|last1=Burns|first1=C|last2=Pastoor|first2=T|date=2018|title=Pyrethroid epidemiology: a quality-based review|journal=[[Critical Reviews in Toxicology]]|volume=48|issue=4|pages=297–311|doi=10.1080/10408444.2017.1423463|pmid=29389244|doi-access=free}}</ref> However, large doses can cause acute poisoning, which is rarely life threatening. Typical symptoms include facial [[paresthesia]], itching, burning, dizziness, nausea, vomiting and more severe cases of muscle twitching. Severe poisoning is often caused by ingestion of pyrethroids and can result in a variety of symptoms like seizures, [[coma]], bleeding or [[pulmonary edema]].<ref name=":0" /> There is an association of pyrethroids with poorer early social-emotional and language development.<ref name=VHEMBE />

===Other organisms===
Pyrethroids are very toxic to [[cat]]s, but not to [[dog]]s. Poisoning in cats can result in seizures, fever, [[ataxia]] and even death. Poisoning can occur if pyrethroid containing [[flea treatment]] products, which are intended for dogs, are used on cats. The livers of cats detoxify pyrethroids via [[glucuronidation]] more poorly than dogs, which is the cause of this difference.<ref>{{Cite journal|last1=Boland|first1=L|last2=Angles|first2=J|date=2010|title=Feline permethrin toxicity: retrospective study of 42 cases|journal=[[Journal of Feline Medicine and Surgery]]|volume=12|issue=2|pages=61–71|doi=10.1016/j.jfms.2009.09.018|issn=1532-2750|pmid=19897392|s2cid=206051191|pmc=10911430}}</ref> Aside from cats, pyrethroids are typically not toxic to [[mammal]]s or [[bird]]s.<ref>{{Cite book|title=Veterinary toxicology: basic and clinical principles|vauthors=Gupta RC|publisher=Elsevier|year=2007|isbn=978-0-08-048160-9|edition=1st|pages=676–677|doi=10.1016/B978-012370467-2/50153-X|display-authors=etal}}</ref> They are often toxic to [[fish]], [[reptile]]s and [[amphibian]]s.<ref>{{Cite journal|display-authors=etal|vauthors=Ortiz-Santaliestra ME|date=2018|title=Validity of fish, birds and mammals as surrogates for amphibians and reptiles in pesticide toxicity assessment|journal=[[Ecotoxicology (journal)|Ecotoxicology]]|volume=27|issue=7|pages=819–833|doi=10.1007/s10646-018-1911-y|pmid=29492806|bibcode=2018Ecotx..27..819O |s2cid=3604324}}</ref>

==Resistance==
{{further|Insecticide resistance}}
The use of pyrethroids as insecticides has led to the development of widespread resistance to them among some insect populations, especially mosquitoes.<ref name="Jeran-et-al-2020">{{cite journal | last1=Jeran | first1=Nina | last2=Grdiša | first2=Martina | last3=Varga | first3=Filip | last4=Šatović | first4=Zlatko | last5=Liber | first5=Zlatko | last6=Dabić | first6=Dario | last7=Biošić | first7=Martina | title=Pyrethrin from Dalmatian pyrethrum (''Tanacetum cinerariifolium''/Trevir./Sch. Bip.): biosynthesis, biological activity, methods of extraction and determination | journal=[[Phytochemistry Reviews]] | publisher=[[Springer Science+Business Media]]| volume=20 | issue=5 | date=2020-10-06 | issn=1568-7767 | doi=10.1007/s11101-020-09724-2 | pages=875–905| s2cid=225152789|id=[[Phytochemical Society of Europe]]+[[Phytochemical Society of North America]]. MG [[ORCID]]: [http://orcid.org/0000-0002-4584-4851 0000-0002-4584-4851])}}</ref>

Pyrethroids have been used against bedbugs, but resistant populations have developed to them.<ref name="JAMA2009">{{cite journal |doi=10.1001/jama.2009.405 |pmid=19336711 |title=Bed Bugs ''Cimex lectularius'' and Clinical Consequences of Their Bites |journal=[[JAMA]]|volume=301 |issue=13 |pages=1358–66 |year=2009 |last1=Goddard |first1=Jerome |last2=Deshazo |first2=R |doi-access= }}</ref><ref name="Kolb2009">{{cite journal |doi=10.1111/j.1529-8019.2009.01246.x |pmid=19580578 |title=Bedbugs |journal=[[Dermatologic Therapy]]|volume=22 |issue=4 |pages=347–52 |year=2009 |last1=Kolb |first1=Adam |last2=Needham |first2=Glen R |last3=Neyman |first3=Kimberly M |last4=High |first4=Whitney A |s2cid=221648188 |doi-access=free }}</ref><ref name="voiland">Voiland, Adam. [http://health.usnews.com/usnews/health/articles/070708/16bedbug.htm "You May not be Alone"] {{webarchive|url=https://web.archive.org/web/20111107010535/http://health.usnews.com/usnews/health/articles/070708/16bedbug.htm |date=2011-11-07 }} U.S. News & World Report 16 July 2007, Vol. 143, Issue 2, p53–54.</ref><ref>{{cite journal |doi=10.1603/0022-2585(2008)45[1092:BAMAOD]2.0.CO;2 |pmid=19058634 |year=2008 |volume=45 |issue=6 |pages=1092–101 |title=Biochemical and Molecular Analysis of Deltamethrin Resistance in the Common Bed Bug (Hemiptera: Cimicidae) |journal=[[Journal of Medical Entomology]]|last1=Yoon |first1=Kyong Sup |last2=Kwon |first2=Deok Ho |last3=Strycharz |first3=Joseph P |last4=Hollingsworth |first4=Craig S |last5=Lee |first5=Si Hyeock |last6=Clark |first6=J. Marshall |doi-broken-date=16 January 2025 |s2cid=27422270 }}</ref> Populations of [[diamondback moth]]s have also commonly developed resistance to pyrethroids<ref>{{cite journal|last1=Leibee|first1=Gary L.|last2=Savage|first2=Kenneth E.|year=1992|title=Evaluation of Selected Insecticides for Control of Diamondback Moth and Cabbage Looper in Cabbage in Central Florida with Observations on Insecticide Resistance in the Diamondback Moth|journal=The Florida Entomologist|volume=75|issue=4|pages=585|doi=10.2307/3496140|issn=0015-4040|jstor=3496140}}</ref>{{better source needed|date=January 2022}} {{endash}} including in U.S. states [[North Dakota]]<ref name="NDSUExt">{{cite web | title=Pyrethroid Complaints for Diamondback Moth Control in Canola (08/26/21) | website=[[NDSU Extension|NDSU Agriculture and Extension]] | date=2021-08-26 | url=http://www.ag.ndsu.edu:8000/agriculture/ag-hub/ag-topics/crop-production/crop-pest-report/entomology/pyrethroid-complaints-diamondback-moth | access-date=2022-01-08 }}{{Dead link|date=December 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> and [[Wisconsin]]<ref name="WiscHortDBM">{{cite web | last=Marsden | first=Christy | title=Diamondback Moth | website=[[Wisconsin Horticulture]] | date=2021-10-15 | url=http://hort.extension.wisc.edu/articles/diamondback-moth/ | access-date=2022-01-08}}</ref> while pyrethroids are still recommended in [[California]].<ref name="UCANRDBM">{{cite web | url=http://www2.ipm.ucanr.edu/agriculture/floriculture-and-ornamental-nurseries/Diamondback-moth/ | title=Diamondback Moth - Floriculture and Ornamental Nurseries Pest Management Guidelines | website=[[University of California Agriculture and Natural Resources]] (UCANR)}}</ref> Various mosquito populations have been discovered to have a high level of resistance, including ''[[Anopheles gambiae sensu lato|Anopheles gambiae s.l.]]'' in [[West Africa]] by Chandre et al 1999 through Pwalia et al 2019, ''[[Anopheles arabiensis|A. arabiensis]]'' in [[Sudan]] by Ismail et al 2018 and [[The Gambia]] by Opondo et al 2019, and ''[[Aedes aegypti]]'' in [[South East Asia]] by Amelia-Yap et al 2018, [[Papua New Guinea]] by Demok et al 2019, and various other locations by Smith et al 2016.<ref name="Jeran-et-al-2020" />

{{Vanchor|[[Knockdown resistance]]|knockdown resistance|kdr}} (''kdr'') is one of the stronger kinds of resistance.<ref name="Molecular" /> ''kdr'' [[mutation]]s confer [[target-site resistance]] to [[DDT]] and pyrethroids and [[cross-resistance]] to DDT.<ref name="Molecular" /> Most ''kdr'' mutations are within or proximate to the two arthropod [[sodium channel]] genes.<ref name="Molecular">{{cite journal|year=2014|publisher=[[Elsevier BV]]|pages=1–17|first8=Boris|first7=Kristopher|volume=50|first6=Lingxin|first5=Peng|first4=Yoshiko|first3=Frank|first2=Yuzhe|first1=Ke|last8=Zhorov|last7=Silver|last6=Wang|last5=Xu|last4=Nomura|last3=Rinkevich|last2=Du|last1=Dong|journal=[[Insect Biochemistry and Molecular Biology]]|issn=0965-1748|id=[[NIHMSID]]: 582398|s2cid=6332754|pmc=4484874|pmid=24704279|doi=10.1016/j.ibmb.2014.03.012|title=Molecular biology of insect sodium channels and pyrethroid resistance|bibcode=2014IBMB...50....1D }}</ref>

==History==
Pyrethroids were introduced by a team of [[Rothamsted Research]] scientists in the 1960s and 1970s following the elucidation of the structures of pyrethrin I and II by [[Hermann Staudinger]] and [[Leopold Ružička]] in the 1920s.<ref name="StaudingerRuzicka1924">{{cite journal |doi=10.1002/hlca.19240070124 |title=Insektentötende Stoffe I. Über Isolierung und Konstitution des wirksamen Teiles des dalmatinischen Insektenpulvers |trans-title=Insecticidal substances I. On isolation and constitution of the active part of the Dalmatian insect powder |journal=[[Helvetica Chimica Acta]]|volume=7 |issue=1 |pages=177–201 |year=1924 |last1=Staudinger |first1=H |last2=Ruzicka |first2=L }}</ref> The pyrethroids represented a major advancement in the chemistry that would synthesize the analog of the natural version found in [[Chrysanthemum#Insecticidal uses|pyrethrum]]. Its insecticidal activity has relatively low [[mammal]]ian [[toxicity]] and an unusually fast biodegradation. Their development coincided with the identification of problems with [[DDT]] use. Their work consisted firstly of identifying the most active components of [[pyrethrum]], extracted from East African chrysanthemum flowers and long known to have insecticidal properties. Pyrethrum rapidly knocks down flying insects but has negligible persistence — which is good for the environment but gives poor efficacy when applied in the field. Pyrethroids are essentially chemically stabilized forms of natural pyrethrum and belong to IRAC MoA group 3 (they interfere with sodium transport in insect nerve cells).<ref name=resistance>{{cite journal |doi=10.1016/j.ibmb.2012.03.008 |pmid=22504519 |title=Identification of mutations associated with pyrethroid resistance in the voltage-gated sodium channel of the tomato leaf miner (Tuta absoluta) |journal=[[Insect Biochemistry and Molecular Biology]]|volume=42 |issue=7 |pages=506–13 |year=2012 |last1=Haddi |first1=Khalid |last2=Berger |first2=Madeleine |last3=Bielza |first3=Pablo |last4=Cifuentes |first4=Dina |last5=Field |first5=Linda M |last6=Gorman |first6=Kevin |last7=Rapisarda |first7=Carmelo |last8=Williamson |first8=Martin S |last9=Bass |first9=Chris |doi-access=free |bibcode=2012IBMB...42..506H |url=https://repository.rothamsted.ac.uk/download/d740e025fe45d0f2cca5d0f582176c8641c90afcf8dc497d6e7ed7fb7407c889/4615152/1-s2.0-S0965174812000471-main.pdf }}</ref>

The ''first-generation pyrethroids'', developed in the 1960s, include [[bioallethrin]], [[tetramethrin]], [[resmethrin]], and bioresmethrin. They are more active than the natural pyrethrum but are unstable in sunlight. With the 91/414/EEC review,<ref>{{cite web|url=http://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:31991L0414|title=EUR-Lex - 31991L0414 - EN - EUR-Lex|work=europa.eu|date=15 July 1991 }}</ref> many 1st-generation compounds have not been included on Annex 1, probably because the market is not big enough to warrant the costs of re-registration (rather than any special concerns about safety).

By 1974, the Rothamsted team had discovered a ''second generation'' of more persistent compounds notably: [[permethrin]], [[cypermethrin]] and [[deltamethrin]]. They are substantially more resistant to degradation by light and air, thus making them suitable for use in [[agriculture]], but they have significantly higher mammalian toxicities. Over the subsequent decades these derivatives were followed with other proprietary compounds such as [[fenvalerate]], [[lambda-cyhalothrin]] and beta-[[cyfluthrin]]. Most patents have now expired, making these compounds cheap and therefore popular (although permethrin and fenvalerate have not been re-registered under the 91/414/EEC process).

==References==
{{Reflist|refs=

<ref name="Soderlund-Bloomquist-1989">{{cite journal | last1=Soderlund | first1=David M | last2=Bloomquist | first2=Jeffrey R | title=Neurotoxic Actions of Pyrethroid Insecticides | journal=[[Annual Review of Entomology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=34 | issue=1 | year=1989 | issn=0066-4170 | doi=10.1146/annurev.en.34.010189.000453 | pages=77–96 | s2cid=31881940 | pmid=2539040}}</ref>

}}

{{Insecticides}}

[[Category:Pyrethroids]]
[[Category:Household chemicals]]