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| Names | |
|---|---|
| IUPAC name Diethyl 2-[(dimethoxyphosphorothioyl)sulfanyl]butanedioate | |
| Other names 2-(Dimethoxyphosphinothioylthio) butanedioic acid diethyl ester Malathion Carbofos Maldison Mercaptothion Ortho malathion | |
| Identifiers | |
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3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
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| DrugBank |
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| ECHA InfoCard | 100.004.089 |
| KEGG |
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| UNII | |
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| Properties | |
| C10H19O6PS2 | |
| Molar mass | 330.358021 |
| Appearance | Clear colorless liquid |
| Density | 1.23 g/cm3 |
| Melting point | 2.9 °C (37.2 °F; 276.0 K) |
| Boiling point | 156 to 157 °C (313 to 315 °F; 429 to 430 K) at 0.7 mmHg |
| 145 mg/L at 20 °C[1] | |
| Solubility | Soluble in ethanol and acetone; very soluble in ethyl ether |
| logP | 2.36 (octanol/water)[2] |
| Pharmacology | |
| P03AX03 (WHO) QP53AF12 (WHO) | |
| Hazards | |
| Flash point | 163 °C; 325 °F; 436 K (greater than)[3] |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) | 290 mg/kg (rat, oral) 190 mg/kg (mouse, oral) 570 mg/kg (guinea pig, oral)[4] |
LC50 (median concentration) | 84.6 mg/m3 (rat, 4 hr)[4] |
LCLo (lowest published) | 10 mg/m3 (cat, 4 hr)[4] |
| NIOSH (US health exposure limits): | |
PEL (Permissible) | TWA 15 mg/m3 [skin][3] |
REL (Recommended) | TWA 10 mg/m3 [skin][3] |
IDLH (Immediate danger) | 250 mg/m3[3] |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Malathion is anorganophosphateinsecticide which acts as anacetylcholinesterase inhibitor. In theUSSR, it was known ascarbophos, inNew Zealand andAustralia asmaldison and inSouth Africa asmercaptothion.
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.[5] In the US, it is the most commonly used organophosphate insecticide.[6]
A malathion mixture withcorn syrup was used in the 1980s in Australia and California to combat theMediterranean fruit fly.[7] In Canada and the US starting in the early 2000s, malathion was sprayed in many cities to combatwest Nile virus.[8] 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].
In the United Kingdom, malathion was withdrawn from sale in 2002.[9]
Malathion is anacetylcholinesterase inhibitor, a diverse family of chemicals. Upon uptake into the target organism, it binds irreversibly to theserine 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 ofacetylcholine at the synapse.[10]
Malathion is produced by the addition ofdimethyl dithiophosphoric acid todiethyl maleate ordiethyl fumarate. The compound is chiral but is used as aracemate.[citation needed]
Malathion in low doses (0.5% preparations) is used as a treatment for:
Preparations include Derbac-M, Prioderm, Quellada-M[15] and Ovide.[16]
Malathion is of low toxicity. In arthropods it is metabolized intomalaoxon[17] which is 61x more toxic,[18] being a more potent inhibitor of acetylcholinesterase.[19] According to theUnited States Environmental Protection Agency, no reliable information is available on adverse health effects of chronic exposure.[20]
In 1989, Malathion was sprayed over a 1,400 sq mi (3,600 km2) area to controlan 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.[21]
Malathion is classified by theIARC asprobable carcinogen (group 2A). Malathion is classified by US EPA as having "suggestive evidence of carcinogenicity".[18] 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 withnon-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.[22]
Malathion is toxic toleopard frog tadpoles.[23]
Malathion is of low toxicity; however, absorption or ingestion into the human body readily results in its metabolism tomalaoxon, which is substantially more toxic.[24] 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,[24] and malaoxon is 1,000 times more potent than malathion in terms of its acetylcholinesterase inhibition.[19] 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.[25]
Because it is an acetylcholinesterase inhibitor, this resistance is a type ofAChEI resistance.[17] Malathion resistance is thought to always be due to either increasedcarboxylesterase concentrations or alteredacetylcholinesterases.[17] COE because it metabolizes malathion but intonon-malaoxon products, altered AChEs because we mean specifically those altered to be less sensitive to malathion and malaoxon.[17]
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.
