Isomalathion is an impurity found in some batches of

malathion 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. The compound's name is presumably ...

. Whereas the structure of malation is, generically, RSP(S)(OCH₃)₂, the connectivity of isomalathion is RSPO(SCH₃)(OCH₃). It arises by heating malathion. Being significantly more toxic to humans than malathion, it has resulted in human poisonings. In 1976, numerous

malaria Malaria is a Mosquito-borne disease, mosquito-borne infectious disease that affects vertebrates and ''Anopheles'' mosquitoes. Human malaria causes Signs and symptoms, symptoms that typically include fever, Fatigue (medical), fatigue, vomitin ...

workers in

Pakistan Pakistan, officially the Islamic Republic of Pakistan, is a country in South Asia. It is the List of countries and dependencies by population, fifth-most populous country, with a population of over 241.5 million, having the Islam by country# ...

were poisoned by isomalathion. It is an inhibitor of carboxyesterase.

References

Phosphorodithioates Succinate esters {{biochem-stub