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

MALATHION 74
3. HEALTH EFFECTS
Metabolic Effects. The only study that specifically reported metabolic effects was that of Zivot et al.
(1993) in which severe metabolic acidosis was observed in an 80-year-old woman who ingested an
unspecified, but fatal, amount of malathion. Anion gap acidosis is common in organophosphate
poisoning from poor tissue perfusion (Aaron and Howland 1998). No relevant information was found in
animal studies.
Other Systemic Effects. The incidence of pancreatic involvement in malathion intoxication was
investigated in 75 patients who ingested unspecified amounts of liquid formulations of the pesticide
(Dagli and Shaikh 1983). Serum amylase levels over 500 units (normal range 80–200 units) in
10 patients suggested that these patients had acute pancreatitis, whereas milder elevations in 37 patients
suggested mild pancreatic dysfunction; all amylase levels returned to within normal values within 3 days
following treatment for organophosphate poisoning. Dagli and Shaikh (1983) stated that the occurrence
of pancreatitis was the result of functional ductal obstruction caused by an increase in exocrine flow rate,
which is consistent with activation of muscarinic receptors in the pancreas by malathion. The occurrence
of pancreatic involvement could not be confirmed by surgery or autopsy because all patients recovered.
Hyperglycemia and/or glucosuria were reported in several cases of acute malathion poisoning (Crowley
and Johns 1966; Dive et al. 1994; Healy 1959; Zivot et al. 1993). The exact cause of these findings is
unknown.
As previously mentioned, there are some oral studies in animals that provided information on food and/or
water consumption during administration of malathion. For example, decreased food intake was reported
in rats given 163 mg/kg/day malathion in the diet for 7 days (Ojha et al. (1992) and in water intake when
malathion was administered in the drinking water at a target dose of 95 mg/kg/day for 14 days (Lox
1985). A chronic-duration study reported a significant decrease in food consumption in rats fed
approximately 1,476 mg/kg/day malathion in the diet for 18 months (Slauter 1994). These effects may
reflect aversion to the taste or smell of the diet and have no toxicological significance. There is no
evidence that malathion may affect food utilization.
3.2.2.3 Immunological and Lymphoreticular Effects
No information was located regarding immunological effects in humans following oral exposure to
malathion. In animals, the effects of malathion on the immune system have been examined in numerous