toxicological profile for malathion - Agency for Toxic Substances and ...

MALATHION A-8
APPENDIX A
If an inhalation study in animals, list conversion factors used in determining human equivalent dose: Not
applicable.
Was a conversion used from intermittent to continuous exposure? No.
Other additional studies or pertinent information that lend support to this MRL: Malathion is an
organophosphate pesticide and as such, its main target of toxicity is the nervous system (Abou-Donia
1995; Ecobichon 1994; Koelle 1994; Taylor 1996). Within the nervous system, malathion and its active
metabolite, malaoxon, inhibit acetylcholinesterase, the enzyme that terminates the action of the
neurotransmitter acetylcholine. The effects of malathion have been well documented in studies in
animals and also in humans, although in the latter case, mostly from case reports of accidental or
intentional ingestion of high amounts of malathion. The study by Moeller and Rider (1962) was the only
available study of controlled ingestion of malathion in humans for review. Most of the studies in animals,
while supporting the human data, have been conducted with higher dose levels of malathion.
Agency Contact (Chemical Manager): Jewell D. Wilson, Ph.D.