View source for Permethrin

{{chembox
| Watchedfields = changed
| verifiedrevid = 308372845
|   Name = Permethrin
|   ImageFile = Permethrin-2D-skeletal.png
|   ImageSize = 300px
|   ImageName = Chemical structure of permethrin
|   IUPACName =  3-Phenoxybenzyl<br />
(1RS)-cis,trans-3-(2,2-dichlorovinyl)<br />-2,2-dimethylcyclopropanecarboxylate
| Section1 = {{Chembox Identifiers
|   CASNo_Ref = {{cascite}}
| CASNo = 52645-53-1
|   ATCCode_prefix = P03
|   ATCCode_suffix = AC04
|   ATC_Supplemental = {{ATCvet|P53|AC04}}
|   SMILES = c3ccccc3Oc(c2)cccc2COC(=O)<br />C1C(C1(C)C)C=C(Cl)Cl
  }}
| Section2 = {{Chembox Properties
|   Formula = C<sub>21</sub>H<sub>20</sub>Cl<sub>2</sub>O<sub>3</sub>
|   MolarMass = 391.28 g/mol
|   Density = 1.19 g/cm³, solid
|   Solubility = Insoluble (5.5 x 10<sup>-3</sup> [[Parts per million|ppm]])
|   Appearance = colourless crystals
|   MeltingPtC = 34
|   BoilingPtC = 200
  }}
| Section7 = {{Chembox Hazards
|   ExternalMSDS = [http://physchem.ox.ac.uk/MSDS/PE/permethrin.html External MSDS]
|   MainHazards = Irritating to skin and eyes,<br /> damaging to lungs
  }}
| Section8 = {{Chembox Related
|   Function = [[pyrethroid]]s
|   OtherFunctn = [[Bifenthrin]]<br />[[Deltamethrin]]
|   OtherCpds =
  }}
}}

'''Permethrin''' is a common [[chemical synthesis|synthetic]] chemical, widely used as an [[insecticide]], [[acaricide]], and [[insect repellent]]. It belongs to the family of synthetic chemicals called [[pyrethroid]]s and functions as a [[neurotoxin]], affecting [[neuron]] [[cell membrane|membrane]]s by prolonging sodium channel activation.  It is not known to rapidly harm most [[mammal]]s or [[bird]]s, but is highly toxic to [[cat]]s and [[fish]].<ref>{{cite web |publisher=ASPCA National Animal Poison Control Center |title=Permethrin Hazards For Cats |url=http://www.vetprof.com/clientinfo/permethrincats.html}}</ref><ref>{{cite web |publisher=About.com |title=Cat Flea Control Products Warning |author=Franny Syufy |url=http://cats.about.com/cs/healthissues/a/permethrin.htm}}</ref> It generally has a low mammalian toxicity and is poorly absorbed by skin.<ref>http://pmep.cce.cornell.edu/profiles/extoxnet/metiram-propoxur/permethrin-ext.html</ref>

==Uses==
Permethrin is used:
* as an insecticide:
** in agriculture, to protect crops
** in agriculture, to kill livestock parasites
** for industrial/domestic insect control
* as an insect repellent or insect screen
** in timber treatment
** as a personal protective measure (cloth impregnant notably used for US military uniforms and mosquito nets)
** in pet collars.

===Agriculture and forestry===
In agriculture, permethrin is mainly used on [[cotton]], [[wheat]], [[maize]], and [[alfalfa]] crops, and is also used to kill [[parasite]]s on [[chicken]]s and other [[poultry]].{{Citation needed|date=June 2010}} It is also extensively used in Europe as a timber treatment against wood-boring beetle ([[woodworm]]).{{Citation needed|date=June 2010}} Its use is controversial because, as a [[broad-spectrum]] chemical, it kills indiscriminately; as well as the intended pests, it can harm beneficial insects including [[honey bee]]s, aquatic life,<ref>{{cite journal | author = R. H. Ian | title = Aquatic organisms and pyrethroids | year = 1989 | journal = [[Pesticide Science]] | volume = 27 | issue = 4 | pages = 429–457 | doi = 10.1002/ps.2780270408}}</ref> and small mammals such as [[mouse|mice]].

===Personal insect control===
Permethrin is toxic to cats. Many cats die after being given flea treatments intended for dogs, or by contact with dogs who have recently been treated with permethrin.<ref>{{cite journal | author = P-J Linnett | title = Permethrin toxicosis in cats | year = 2008 | journal = [[Australian Veterinary Journal]] | volume = 86 | issue = 1-2 | pages = 32–35 | doi = 10.1111/j.1751-0813.2007.00198.x | pmid = 18271821 | last1 = Linnett | first1 = PJ}}</ref>

Permethrin is also used in healthcare, to eradicate parasites such as [[head lice]] and mites responsible for [[scabies]], and in industrial and domestic settings to control pests such as [[ant]]s and [[termite]]s. However, the [[British National Formulary]] states that permethrin has low efficiency in eradicating head lice.

Permethrin kills ticks on contact with treated clothing. A method of reducing deer tick populations in terms of rodent vectors involves utilizing biodegradable cardboard tubes stuffed with permethrin-treated cotton. Mice collect the cotton for lining their nests. Permethrin on the cotton instantly kills any immature ticks that are feeding on the mice.  It is important to put the tubes where mice will find them, such as in dense, dark brush, or at the base of a log; mice are unlikely to gather cotton from an open lawn. According to the [[Connecticut Department of Public Health]], permethrin "has low mammalian toxicity, is poorly absorbed through the skin and is rapidly inactivated by the body. Skin reactions have been uncommon."<ref>{{cite web | url = http://www.dph.state.ct.us/BCH/infectiousdise/tickborne/tick.htm#Permethrin | title = Tick Bite Prevention | author = Kirby C. Stafford III | date = February 1999 | publisher = Connecticut Department of Public Health}}</ref> Permethrin is also used on humans for lice or scabies; the common prescription is Permethrin with 5% concentration for scabies, and OTC (over the counter) treatment for head lice/crabs is usually permethrin with 1% concentration.

Permethrin is used in tropical areas to prevent [[mosquito]]-borne disease such as [[dengue fever]] and [[malaria]]. [[Mosquito nets]] used to cover beds may be treated with a solution of permethrin.  This increases the effectiveness of the bed net by killing parasitic insects before they are able to find gaps or holes in the net. Malaria kills 1-3 million people per year. Military personnel training in malaria-endemic areas may be instructed to treat their uniforms with permethrin as well. An application should last several washes.

==Stereochemistry==
Permethrin has four [[Stereoisomerism|stereoisomers]] (two [[enantiomer|enantiomeric pairs]]), arising from the two [[stereocenter|stereocentres]] in the [[cyclopropane]] ring.  The ''[[Cis-trans isomerism|trans]]'' enantiomeric pair is known as '''transpermethrin'''.  

<gallery>
Image:(1S)-trans-permethrin.svg|<center>''(1S)''-''trans''-acid moiety</center>
Image:Cis-permethrin-A-2D-skeletal.png |<center>one ''cis'' [[enantiomer]]</center>
Image:Cis-permethrin-B-2D-skeletal.png |<center>the other ''cis'' enantiomer</center>
</gallery>

==Toxicology and safety==
Permethrin acts as [[neurotoxin]], slowing down the nervous system through binding to sodium channels. This action is negatively correlated to temperature, thus generally showing more acute effects on cold-blooded animals (insects, fish, frogs...) over warm-blooded animals (mammals and birds):
* Permethrin is extremely toxic to fish and aquatic life in general, so extreme care must be taken when using products containing permethrin near water sources.
* Permethrin is also highly toxic to cats and flea and tick repellent formulas intended and labeled for (the more resistant) dogs may contain permethrin and cause feline permethrin toxicosis in cats.<ref>[http://news.bbc.co.uk/1/low/uk/7088397.stm BBC News report "Cats 'killed by flea treatment'" ]</ref>
* Very high doses will have tangible neurotoxic effects on mammals and birds, including human beings.

Permethrin does not present any notable genotoxicity or immunotoxicity in humans and farm animals.

Permethrin is classified by the [[United States Environmental Protection Agency]] (EPA) a likely human [[carcinogen]], based on reproducible studies in which mice fed permethrin developed liver and lung [[tumor]]s.<ref>[http://www.epa.gov/oppsrrd1/REDs/factsheets/permethrin_fs.htm Permethrin Facts], US EPA, June 2006.</ref> Carcinogenic action in nasal mucosal cells for inhalation exposure is suspected due to observed genotoxicity in human tissue samples, and in rat livers the evidence of increased preneoplastic lesions lends concern over oral exposure.<ref>{{cite journal | author = M. Tisch, P. Schmezer, M. Faulde, A. Groh and H. Maier | title = Genotoxicity studies on permethrin, DEET and diazinon in primary human nasal mucosal cells | year = 2002 | journal = [[European Archives of Oto-Rhino-Laryngology]] | volume = 259 | issue = 3 | pages = 150–153 | doi = 10.1007/s004050100406}}</ref><ref>{{cite journal | author = K. Hakoi, R. Cabral, T. Hoshiya, R. Hasegawa, T. Shirai and N. Ito | title = Analysis of carcinogenic activity of some pesticides in a medium-term liver bioassay in the rat | year = 1992 | journal = [[Teratogenesis, Carcinogenesis, and Mutagenesis]] | volume = 12 | issue = 6 | pages = 269–276 | doi = 10.1002/tcm.1770120605}}</ref>

Studies by Bloomquist et al., 2002 <ref>[http://www.ncbi.nlm.nih.gov/pubmed/12428726] Neurotoxicology. 2002 Oct;23(4-5):537-44.</ref> suggested a link of permethrin exposure to [[Parkinson's disease]], including very small (per kg.) exposures.
<blockquote>"Our studies have documented low-dose effects of permethrin, doses below one-one thousandth of a lethal dose for a mouse, with effects on those brain pathways involved in Parkinson's Disease [...] We have found effects consistent with a pre-parkinsonsian condition, but not yet full-blown parkinsonism."&nbsp;<ref>[http://news.bbc.co.uk/2/hi/health/2881431.stm] BBC News, March 2006.</ref><ref>[http://www.cals.vt.edu/news/archives/20030324.html] Virginia Tech, March 2003.</ref></blockquote> A more recent study by the same researcher concluded that <blockquote>"long-term, low-dose exposure to permethrin alone did not cause signs of neurotoxicity to striatal dopaminergic neural terminals, or enhance the effects of MPTP. We conclude that under typical use conditions, permethrin poses little Parkinsonian hazard to humans, including when impregnated into clothing for control of biting flies"<ref>
{{cite journal 
| author = Kou J, Bloomquist JR.
| title =  Neurotoxicity in murine striatal dopaminergic pathways following long-term application of low doses of permethrin and MPTP.
| year = 2007 
| journal = Toxicol Lett
| volume = 171
| issue = 3 
| pages = 154–161
| doi = 10.1016/j.toxlet.2007.05.005
| pmid = 17597311
| last1 = Kou 
| first1 = J 
| last2 = Bloomquist 
| first2 = JR 
}}</ref>
</blockquote> 

Due to high toxicity for aquatic life, permethrin and permethrin-contaminated water should be properly disposed of. Degradation is quick and should the chemical be trashed far from any aquatic life, the negative effects would be minimized. Ideally, in a non-industrial context, the contaminant can be set in the light to induce photodegradation. Contaminated water set in direct sunlight exposure will be cleared of the permethrin and any known pollutant subproducts after a few hours.

Recently, in [[South Africa]], residues of permethrin were found in breast milk, together with DDT, in an area that experienced [[DDT]] treatment for malaria control, as well as the use of pyrethroids in small-scale agriculture.<ref>{{cite journal | author = H. Bouwman, B. Sereda and H. M. Meinhardt | title = Simultaneous presence of DDT and pyrethroid residues in human breast milk from a malaria endemic area in South Africa | year = 2006 | journal = [[Environmental Pollution]] | volume = 144 | issue = 3 | pages = 902–917 | doi = 10.1016/j.envpol.2006.02.002 | pmid = 16564119 | last1 = Bouwman | first1 = H | last2 = Sereda | first2 = B | last3 = Meinhardt | first3 = HM}}</ref>

The use of the substance has been restricted by the United States government, although such restriction is outdated now.<ref name=rupr>{{cite web
  | last = [[Environmental Protection Agency]]
  | first =
  | authorlink =
  | coauthors =
  | title = Restricted Use Products (RUP) Report: Six Month Summary List
  | work =
  | publisher =
  | date =
  | url = http://www.epa.gov/opprd001/rup/rup6mols.htm
  | doi =
  | accessdate = 1 December 2009}}</ref>

===Human exposure===
Excessive exposure to permethrin can cause nausea, headache, muscle weakness, salivation, shortness of breath and seizures. Worker exposure to the chemical can be monitored by measurement of the urinary metabolites, while severe overdosage may be confirmed by quantitation of permethrin in serum or plasma.<ref>R. Baselt, ''Disposition of Toxic Drugs and Chemicals in Man'', 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 1215-1216.</ref>

==See also==
* [[Methoprene]]
* [[Pyrethrin]]

==References==
{{Reflist|2}}

==External links==
* [http://www.nap.edu/catalog.php?record_id=9274 "Health Effects of Permethrin-Impregnated Army Battle-Dress Uniforms", National Research Council (1994, US)]
* [http://www.ema.europa.eu/pdfs/vet/mrls/011296en.pdf "Permethrin summary report", Committee for Veterinary Products, European Agency for the Evaluation of Medical Products (1998, EU(]
* [http://news.bbc.co.uk/1/hi/health/2881431.stm Pesticide link to Parkinson Disease]
* [http://npic.orst.edu/factsheets/permethrin.pdf Permethrin Fact Sheet - National Pesticide Information Center]
* [http://npic.orst.edu/hottopic/PermethrinTreatedClothes.pdf Permethrin-treated Clothing Hot Topic - National Pesticide Information Center]
* [http://extoxnet.orst.edu/pips/permethr.htm Permethrin Pesticide Information Profile - Extension Toxicology Network]
* [http://www.alanwood.net/pesticides/permethrin.html Permethrin chemical data]

{{Human lice}}
{{Ectoparasiticides}}
{{insecticides}}

[[Category:Insecticides]]
[[Category:Antiparasitic agents]]
[[Category:Household chemicals]]
[[Category:Organochlorides]]
[[Category:Endocrine disruptors]]
[[Category:Phenol ethers]]
[[Category:Pyrethroids]]

[[cs:Permethrin]]
[[de:Permethrin]]
[[es:Permetrina]]
[[fr:Perméthrine]]
[[it:Permetrina]]
[[nl:Permethrin]]
[[pl:Permetryna]]
[[pt:Permetrina]]
[[ru:Перметрин]]
[[fi:Permetriini]]
[[Category:2Fix]]