[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.

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.

[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.