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Malathion is an organophosphate insecticide which is registered for use in the United States since 1956. Malathion is also used to control mosquitoes, flies, household insects, animal parasites and head and body lice. Malathion is classified as slightly toxic and carries the signal word CAUTION on the label.
Toxic effects of Malathion
Malathion is shown to have different toxicities in male and female rats and humans due to metabolism, storage and excretion differences between the sexes. In humans, the lowest dose at which lethal effects have been observed was nearly three times higher for males than for females.
Acute symptoms in humans are nausea, headache, tightness in the chest, and other symptoms typical of acetyl- cholinesterase inhibition, unconsciousness, convulsions, and a “prolonged worsening illness” were also witnessed at higher dosage. Human exposures can occur through ingestion, inhalation, and absorption through the skin.
Malathion has been shown to affect both the adrenal glands and the liver of rats and also has effects on blood clotting in lab animals.
Autopsy samples from a human being who had ingested large amounts of malathion showed a substantial portion in the stomach and intestines, a small amount in fat tissue and no detectable levels in the liver.
Malathion requires conversion to malaoxon to become an active anticholinesterase agent. Most of the occupational evidence indicates a low chronic toxicity for malathion.
Sources ;
http://pmep.cce.cornell.edu/profiles/extoxnet/haloxyfop-methylparathion/malathion-ext.ht