chemical information


Chemical Class:

Organophosphate Pesticides and Metabolites

Found in these people:

Michael Lerner, Andrea Martin

Found in these locations:

Bolinas, CA; Sausalito, CA


Organophosphate (OP) pesticides like malathion cause significant neurotoxicity in laboratory animals and humans, which is not surprising since they were designed to attack the nervous system of insects. Although these pesticides are not as persistent as some environmental chemicals, they are generally more toxic to the young compared to adults. This means that even short-term exposures, such as during pregnancy or childhood, can result in toxicity. Malathion mono-carboxylic acid is a metabolite of malathion.

In humans, malathion can cause typical signs of organophosphate poisoning that include nausea, diarrhea, muscle twitching, blurred vision, headache, respiratory distress, lightheadedness, memory impairment, numbness (especially in the extremities), altered nerve conduction, abnormal heart rate and coma or death at high doses (EPA 2001).

Effects of malathion in laboratory animals include: neurotoxicity (decreased motor activity, excessive salivation, paralysis, altered brain weight, nerve degeneration); eye and skin irritation; lesions of the nasal cavity and larynx; respiratory tract (nasal cavity lesions, lung inflammation and edema); hematological changes; liver toxicity (tumors, increased weight and cellular effects) and thyroid toxicity (tumors and hypothyroidism). Other organs affected include the kidney, spleen, testes and the adrenal gland. Malathion has also been shown to cause mononuclear cell leukemia. Developmental and/or reproductive effects include decreased growth and early pregnancy loss (EPA 2000, California Department of Pesticide Regulation 1997, Sinha 1991, Ozmen 1993, Akhtar 1996).

Malathion Mono-Carboxylic Acid

Organophosphate pesticides were previously marketed for home use and are now used on produce. Known neurotoxins that are particularly toxic to developing fetuses, infants and children.

Malathion Mono-Carboxylic Acid has been found in 2 of the 9 people tested in EWG/Commonweal studies.

Top health concerns for Malathion Mono-Carboxylic Acid (References)

health concern or target organ weight of evidence
Brain and nervous systemunknown

Results for Malathion Mono-Carboxylic Acid

in urine

Showing results from EWG/Commonweal Study #1, industrial chemicals and pesticides in adults

EWG/Commonweal results

  • geometric mean: 1.26 ppb in urine
  • found in 2 of 9 people in the group
ppb in urine 4

Malathion Mono-Carboxylic Acid results

Detailed toxicity classifications (References)

classification governing entity/references
Nervous system toxicity - weight of evidence unknown/unassessedKamel, F. and J. A. Hoppin (2004). Association of pesticide exposure with neurologic dysfunction and disease. Environ Health Perspect 112(9): 950-8.