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

MALATHION 164
3. HEALTH EFFECTS
information is available on dealing with long-term, low-level exposures. This may be due, in part, to the
limited information on toxic effects associated with such exposures. If additional information becomes
available indicating adverse health effects of long-term exposures, then studies examining methods for
mitigating the effects of such exposures would become a data need.
Children’s Susceptibility. Information on the effects of malathion in children is derived mainly
from case reports of accidental ingestion of high amounts of commercial formulations (Ekin 1971; Healy
1959; Jušić and Milić 1978; Tuthill 1958) and cases of dermal exposure (Parker and Chattin 1955; Ramu
et al. 1973). In all of these cases, exposure to malathion resulted in the characteristic signs and symptoms
of organophosphate poisoning: increased salivation and lacrimation, miosis, nausea, vomiting, abdominal
cramps and diarrhea, excessive bronchial secretions and dyspnea, bradycardia and low blood pressure,
and muscle fasciculations. One fatality occurred among the cases described by Ramu et al. (1973). A
case report of aplastic anemia in a 12-year-old child following inhalation of malathion fumes after
fumigation of a home was described by Reeves et al. (1981), but this case seems to be unique; besides,
there is no evidence that malathion was the causal agent. These case reports suggest that there are no
significant differences in the responses between children and adults. Studies in animals have shown that
young animals are more susceptible to the toxicity of high doses of malathion and that this is related to
activities of esterases in various tissues (Brodeur and DuBois 1967; Lu et al. 1965; Mendoza 1976;
Mendoza and Shields 1976, 1977).
Data on developmental effects of malathion in humans are limited. Two studies conducted in California
after aerial spraying of malathion did not find consistent or significant developmental effects in the
offspring from women who were pregnant during the spraying (Grether et al. 1987; Thomas et al. 1992).
An additional study of paternal exposure to malathion found no significant association between exposure
and congenital malformations (García et al. 1998). Most animal data suggest that malathion is not a
developmental toxicant when administered at doses that are not maternally toxic (Khera et al. 1978;
Lochry 1989; Machin and McBride 1989a; Schroeder 1990; Siglin 1985). However, some uncertainty
still remains, largely because of limitations of experimental design or reporting in some studies.
Therefore, a well-designed developmental study would be useful. Also, as previously mentioned, a
developmental neurotoxicity study in rats in which pups are tested at various ages after being exposed in
utero and/or via maternal milk would fill a data gap. There is no evidence that malathion has hormonelike
effects.