Malathion

Malathion is a pesticide that is widely used in agriculture, residential landscaping, public recreation areas, and in public health pest control programs such as mosquito eradication.[https://www.epa.gov/mosquitocontrol/malathion Malathion for mosquito control], US EPA In the US, it is the most commonly used organophosphate insecticide.{{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=1023–1034|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 }}

A malathion mixture with corn syrup was used in the 1980s in Australia and California to combat the Mediterranean fruit fly.{{cite journal |vauthors=Edwards JW, Lee SG, Heath LM, Pisaniello DL |title=Worker exposure and a risk assessment of malathion and fenthion used in the control of Mediterranean fruit fly in South Australia |journal=Environ. Res. |volume=103 |issue=1 |pages=38–45 |year=2007 |pmid=16914134 |doi=10.1016/j.envres.2006.06.001|bibcode=2007ER....103...38E }} In Canada and the US starting in the early 2000s, malathion was sprayed in many cities to combat west Nile virus. Malathion was used over the last couple of decades on a regular basis during summer months to kill mosquitoes, but homeowners were allowed an exemption for their properties if they chose.{{citation needed|date=August 2016}}

In the United Kingdom, malathion was withdrawn from sale in 2002.{{cite web | url=https://www.rhs.org.uk/prevention-protection/withdrawn-chemicals | title=Withdrawn chemicals / RHS Gardening }}

Malathion is an acetylcholinesterase inhibitor, a diverse family of chemicals. Upon uptake into the target organism, it binds irreversibly to the serine residue in the active catalytic site of the cholinesterase enzyme. The resultant phosphoester group is strongly bound to the cholinesterase, and irreversibly deactivates the enzyme which leads to rapid build-up of acetylcholine at the synapse.{{cite journal | doi = 10.2174/1570159X11311030006| pmid = 24179466| pmc = 3648782| title = Acetylcholinesterase Inhibitors: Pharmacology and Toxicology| journal = Current Neuropharmacology| volume = 11| issue = 3| pages = 315–335| year = 2013| last1 = Colovic| first1 = Mirjana B.| last2 = Krstic| first2 = Danijela Z.| last3 = Lazarevic-Pasti| first3 = Tamara D.| last4 = Bondzic| first4 = Aleksandra M.| last5 = Vasic| first5 = Vesna M.}}

Malathion is produced by the addition of dimethyl dithiophosphoric acid to diethyl maleate or diethyl fumarate. The compound is chiral but is used as a racemate.{{cn|date=December 2022}}

Malathion in low doses (0.5% preparations) is used as a treatment for:

• Head lice and body lice. Malathion is approved by the US Food and Drug Administration for treatment of pediculosis.{{Cite web |url= http://guideline.gov/content.aspx?id=12784 |agency= National Guideline Clearinghouse |title= Guidelines for the diagnosis and treatment of pediculosis capitis (head lice) in children and adults 2008 |access-date=2013-01-22 |archive-url= https://web.archive.org/web/20130226070624/http://www.guideline.gov/content.aspx?id=12784 |archive-date=2013-02-26}}{{cite book |author1=Amy J. McMichael |author2= Maria K. Hordinsky |title=Hair and Scalp Diseases: Medical, Surgical, and Cosmetic Treatments |url= https://books.google.com/books?id=W-dT_21KZOIC&pg=PA289 |access-date=27 April 2010 |year=2008 |publisher=Informa Health Care |isbn=978-1-57444-822-1 |pages=289–}} It is claimed to effectively kill both the eggs and the adult lice, but in fact has been shown in UK studies to be only 36% effective on head lice, and less so on their eggs.{{cite journal |vauthors= Downs AM, Stafford KA, Harvey I, Coles GC |title= Evidence for double resistance to permethrin and malathion in head lice |journal=Br. J. Dermatol. |volume=141 |issue=3 |pages=508–11 |year=1999 |pmid= 10583056 |doi=10.1046/j.1365-2133.1999.03046.x |s2cid= 25087526 }} This low efficiency was noted when malathion was applied to lice found on schoolchildren in the Bristol area in the UK, and is caused by the tested population of lice having developed resistance against malathion.
• Scabies{{cite book |author1=Julia A. McMillan |author2=Ralph D. Feigin |author3=Catherine DeAngelis |author4=M. Douglas Jones |title=Oski's pediatrics: principles & practice |url=https://books.google.com/books?id=VbjFQiz8aR0C&pg=RA1-PA1383 |access-date=27 April 2010 |date=1 April 2006 |publisher=Lippincott Williams & Wilkins |isbn=978-0-7817-3894-1 |pages=1–}}

Preparations include Derbac-M, Prioderm, Quellada-MBritish National Formulary 54th Ed. Sept 2007. {{ISBN|978-0-85369-736-7}}. {{ISSN|0260-535X}} and Ovide.{{cite web |url=http://www.medicinescomplete.com/mc/ahfs/current/a384040.htm|title= AHFS Drug Information|date=13 January 2011 |publisher=American Society of Health-System Pharmacists|access-date=17 January 2011}}

Malathion is of low toxicity. In arthropods it is metabolized into malaoxon which is 61x more toxic,{{cite journal |title=Reregistration Eligibility Decision for Malathion (Revised) |date=May 2009 |url=https://archive.epa.gov/pesticides/reregistration/web/pdf/malathion-red-revised.pdf |journal=US Environmental Protection Agency - Prevention, Pesticides and Toxic Substances EPA 738-R-06-030 Journal |pages=9 |vauthors=Keigwin Jr RP}} being a more potent inhibitor of acetylcholinesterase.{{Cite journal |last1=Rodriguez |first1=O. P. |last2=Muth |first2=G. W. |last3=Berkman |first3=C. E. |last4=Kim |first4=K. |last5=Thompson |first5=C. M. |date=February 1997 |title=Inhibition of various cholinesterases with the enantiomers of malaoxon |journal=Bulletin of Environmental Contamination and Toxicology |volume=58 |issue=2 |pages=171–176 |issn=0007-4861 |pmid=8975790 |doi=10.1007/s001289900316 |bibcode=1997BuECT..58..171R |s2cid=29903092}} According to the United States Environmental Protection Agency, no reliable information is available on adverse health effects of chronic exposure.{{cite web |url=http://www.atsdr.cdc.gov/MHMI/mmg154.html |archive-url=https://web.archive.org/web/20021021101747/http://www.atsdr.cdc.gov/MHMI/mmg154.html |archive-date=October 21, 2002 |title=US Department of Health and Human Services: Agency for Toxic Substances and Disease Registry - Medical Management Guidelines for Malathion |access-date=2008-04-02 }}

In 1989, Malathion was sprayed over a {{convert|1400|sqmi|km2|abbr=on}} area to control an outbreak of Mediterranean fruit flies in California. In order to demonstrate the chemical's safety, B. T. Collins, director of the California Conservation Corps, publicly swallowed a mouthful of dilute malathion solution.{{cite magazine |first=Jordan |last=Bonfante |date=1990-01-08 |title=Medfly Madness |url=http://www.time.com/time/magazine/article/0,9171,969129,00.html |access-date=May 21, 2009 |archive-url=https://web.archive.org/web/20080724201507/http://www.time.com/time/magazine/article/0,9171,969129,00.html |archive-date=July 24, 2008 |magazine=TIME}}

Malathion is classified by the IARC as probable carcinogen (group 2A). Malathion is classified by US EPA as having "suggestive evidence of carcinogenicity". This classification was based on the occurrence of liver tumors at excessive doses in mice and female rats and the presence of rare oral and nasal tumors in rats that occurred following exposure to very large doses. Exposure to organophosphates is associated with non-Hodgkin's lymphoma. Malathion used as a fumigant was not associated with increased cancer risk. Between 1993 and 1997, as part of the Agricultural Health Study, no clear association between malathion exposure and cancer was reported.{{Cite web |url=http://npic.orst.edu/ingred/aifact.html|title=Active Ingredient Fact Sheets|website=npic.orst.edu}}

Malathion is toxic to leopard frog tadpoles.{{Cite web | url = https://www.sciencedaily.com/releases/2008/11/081111183041.htm | title = Low Concentrations Of Pesticides Can Become Toxic Mixture For Amphibians | publisher = Science Daily | date = November 18, 2008 | access-date = December 11, 2012}}

Malathion is of low toxicity; however, absorption or ingestion into the human body readily results in its metabolism to malaoxon, which is substantially more toxic. In studies of the effects of long-term exposure to oral ingestion of malaoxon in rats, malaoxon has been shown to be 61 times more toxic than malathion,{{cite journal |title=Reregistration Eligibility Decision for Malathion |url=http://www.epa.gov/pesticides/reregistration/REDs/malathion_red.pdf |journal=US Environmental Protection Agency - Prevention, Pesticides and Toxic Substances EPA 738-R-06-030 Journal |vauthors=Edwards D |pages=9 |date=July 2006 |archive-url=https://web.archive.org/web/20080521072859/http://www.epa.gov/pesticides/reregistration/REDs/malathion_red.pdf |archive-date=2008-05-21}} and malaoxon is 1,000 times more potent than malathion in terms of its acetylcholinesterase inhibition. Indoor spillage of malathion can thus be more poisonous than expected, as malathion breaks down in a confined space into the more toxic malaoxon. It is cleared from the body quickly, in three to five days.{{cite news |work=Los Angeles Times |first=Thomas H. |last=Maugh II |title=Study links pesticide to ADHD in children |date=16 May 2010 |url=https://www.latimes.com/archives/la-xpm-2010-may-16-la-sci-pesticides-20100517-story.html}}

Because it is an acetylcholinesterase inhibitor, this resistance is a type of AChEI resistance. Malathion resistance is thought to always be due to either increased carboxylesterase concentrations or altered acetylcholinesterases. COE because it metabolizes malathion but into non-malaoxon products, altered AChEs because we mean specifically those altered to be less sensitive to malathion and malaoxon.{{cite journal | journal=Pediatrics | issn=0031-4005 | publisher=American Academy of Pediatrics (AAP) | issue=5 | volume=119 | year=2007 | last1=Lebwohl | first1=Mark | last2=Clark | first2=Lily | last3=Levitt | first3=Jacob | pages=965–974 | doi=10.1542/peds.2006-3087 | title=Therapy for Head Lice Based on Life Cycle, Resistance, and Safety Considerations| pmid=17473098 | s2cid=30758188 }}

• Isomalathion
• Pesticide toxicity to bees

{{reflist|refs=

{{cite journal|quote=An extensive re-evaluation of malathion was completed by the US Environmental Protection Agency in 2000. The PMRA has also re-evaluated malathion and approved its use as a mosquito adulticide. |pmc=155959 |pmid=12771072 |journal=Canadian Medical Association Journal |date=2003-05-27 |volume=168 |issue=11 |pages=1427–1430 |title=Pesticide use for West Nile virus |last1=Shapiro |first1=H. |last2=Micucci |first2=S.}}

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• [http://npic.orst.edu/factsheets/archive/malatech.pdf Malathion Technical Fact Sheet - National Pesticide Information Center]
• [http://npic.orst.edu/factsheets/malagen.pdf Malathion General Fact Sheet - National Pesticide Information Center]
• [http://extoxnet.orst.edu/pips/malathio.htm Malathion Pesticide Information Profile - Extension Toxicology Network]
• [https://www.atsdr.cdc.gov/toxfaqs/tfacts154.pdf ATSDR ToxFAQs]
• [https://www.cdc.gov/niosh/npg/npgd0375.html CDC - NIOSH Pocket Guide to Chemical Hazards]
• [http://collection.nlc-bnc.ca/100/200/301/hcan-scan/pmra-arla/proposed_acceptability-e/pacr2003-10/pacr2003-10-e.pdf Re-evaluation of Malathion] by the Pest Management Regulatory Agency of Canada
• {{PPDB|421}}

{{Ectoparasiticides}}

{{Insecticides}}

{{Acetylcholine metabolism and transport modulators}}

{{Consumer Food Safety}}

{{Authority control}}

Category:Acetylcholinesterase inhibitors

Category:Antiparasitic agents

Category:Endocrine disruptors

Category:Organophosphate insecticides

Category:Phosphorodithioates

Category:Ethyl esters

Category:IARC Group 2A carcinogens