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Chlorpyrifos (Molecule of the Month for July 2006)

Dursban, Empire, Eradex, Lorsban & Stipend

Chlorpyrifos is a toxic organophosphate insecticide that is used to control insect pests and are used for killing insects in a range of products including sheep dip.

It works by inhibiting the enzyme acetylcholinesterase. This enzyme is essential as a neurotransmitter, chemicals that interfere with the action of cholinesterase are potent neurotoxins, causing excessive salivation and eye watering in low doses, followed by muscle spasms and ultimately death (examples are snake venom, sarin and VX).

The UK Advisory Committee on Pesticides [ACP] have recommended that use of chlorpyrifos in home and garden products be revoked and have also raised concerns about the safety levels for the pesticide in food. Evidence on the organophosphate's use was reviewed by the committee after the US Environmental Protection Agency announced last year that it was placing restrictions on some of its agricultural uses. But the ACP says that there is enough evidence to support the current Acceptable Daily Intake. The Acceptable Daily Intake is the maximum amount of a chemical that can be consumed every day of a person's life without causing any known harmful consequences.

Formal Chemical Name (IUPAC)
O,O-diethyl O-3,5,6-trichloropyridin-2-yl phosphorothioate




Picture of Chlorpyrifos

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Chlorpyrifos structure
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Picture of Chlorpyrifos

C9 H11 Cl3 N O3 P S

Update by Karl Harrison
(Molecule of the Month for July 2006 )