Malathion

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Malathion
Malathion.png
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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
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.004.089 OOjs UI icon edit-ltr-progressive.svg
KEGG
PubChem CID
UNII
  • InChI=1S/C10H19O6PS2/c1-5-15-9(11)7-8(10(12)16-6-2)19-17(18,13-3)14-4/h8H,5-7H2,1-4H3 Yes check.svgY
    Key: JXSJBGJIGXNWCI-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C10H19O6PS2/c1-5-15-9(11)7-8(10(12)16-6-2)19-17(18,13-3)14-4/h8H,5-7H2,1-4H3
    Key: JXSJBGJIGXNWCI-UHFFFAOYAK
  • O=C(OCC)C(SP(=S)(OC)OC)CC(=O)OCC
Properties
C10H19O6PS2
Molar mass 330.358021
AppearanceClear 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
log P 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):
290 mg/kg (rat, oral)
190 mg/kg (mouse, oral)
570 mg/kg (guinea pig, oral) [4]
84.6 mg/m3 (rat, 4 hr) [4]
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 their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)

Malathion is an organophosphate insecticide which acts as an acetylcholinesterase inhibitor. In the USSR, it was known as carbophos, in New Zealand and Australia as maldison and in South Africa as mercaptothion.

Contents

Pesticide use

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 with corn syrup was used in the 1980s in Australia and California to combat the Mediterranean fruit fly. [7] In Canada and the US starting in the early 2000s, malathion was sprayed in many cities to combat west 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]

Mechanism of action

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. [10]

Production method

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.[ citation needed ]

Medical use

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

Preparations include Derbac-M, Prioderm, Quellada-M [15] and Ovide. [16]

Safety

General

Malathion is of low toxicity. In arthropods it is metabolized into malaoxon [17] which is 61x more toxic, [18] being a more potent inhibitor of acetylcholinesterase. [19] According to the United States Environmental Protection Agency, no reliable information is available on adverse health effects of chronic exposure. [20]

In 1981, Malathion was sprayed over a 1,400 sq mi (3,600 km2) 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. [21]

Carcinogenicity

Malathion is classified by the IARC as probable 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 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. [22]

Amphibians

Malathion is toxic to leopard frog tadpoles. [23]

Risks

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. [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]

Resistance

Because it is an acetylcholinesterase inhibitor, this resistance is a type of AChEI resistance. [17] Malathion resistance is thought to always be due to either increased carboxylesterase concentrations or altered acetylcholinesterases. [17] 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. [17]

See also

Related Research Articles

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<span class="mw-page-title-main">Parathion</span> Chemical compound

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<span class="mw-page-title-main">Chlorpyrifos</span> Chemical compound

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<span class="mw-page-title-main">Ethion</span> Chemical compound

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<span class="mw-page-title-main">Fenthion</span> Chemical compound

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<span class="mw-page-title-main">Azinphos-methyl</span> Chemical compound

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<span class="mw-page-title-main">Dichlorvos</span> Insect killing chemical, organophosphate

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References

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  2. Hansch, C., Leo, A., D. Hoekman. Exploring QSAR - Hydrophobic, Electronic, and Steric Constants. Washington, DC: American Chemical Society., 1995., p. 80
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  5. Malathion for mosquito control, US EPA
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