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

MALATHION 31
3. HEALTH EFFECTS
The only information available regarding respiratory effects in animals following inhalation exposure to
malathion is provided by a study in rats in which whole body exposure to an aerosol concentration of
100 mg/m 3 of malathion (96.4% pure) 6 hours/day, 5 days/week for 13 weeks induced hyperplasia of the
olfactory and larynx epithelia (Beattie 1994). The 100 mg/m 3 exposure concentration, which was the
lowest exposure level tested, was used to derive an intermediate-duration inhalation MRL of 0.02 mg/m 3
for malathion.
Gastrointestinal Effects. The only information on gastrointestinal effects in humans after inhalation
exposure to malathion comes from a study of self-reported symptoms in 22 seamen who may have been
exposed to a single cloud of malathion that escaped from a nearby overheated tank (Markowitz et al.
1986). Compared with a group of controls, the seamen reported significantly more problems such as
diarrhea, constipation, or painful bowel movements when contacted 12 days following the incident. As
previously mentioned, there was no evidence of actual exposure to the chemical.
No studies were located regarding gastrointestinal effects in animals following inhalation exposure to
malathion.
Hematological Effects. As previously mentioned in Section 3.2.1.1, Death, Reeves et al. (1981)
reported the case of a 12-year-old girl who was admitted to the hospital and died from aplastic anemia
6 months after exposure to malathion. Aplastic anemia was diagnosed 2 weeks after a 1-hour exposure to
malathion (unspecified formulation or purity), which makes the evidence that malathion was the causing
agent only circumstantial. This was one of six cases of children exposed to pesticides, and few details are
presented in this brief communication other than the fact that the parents of all six children recalled
previously using the product in the home. A more recent study of 60 workers at a pesticide (primarily
malathion) manufacturing facility who were in direct contact with malathion found an inverse relationship
between hemoglobin concentration and duration of employment (Singaravelu et al. 1998). Eight
individuals who had worked in the processing unit for >20 years had mean hemoglobin levels of
11.30 g/dL compared to 15.5 g/dL measured in four matched controls employed for >20 years. No
information was provided regarding exposure levels or the health status of the workers. The small
number of individuals studied precludes drawing meaningful conclusions from this study.
No studies were located regarding hematological effects in animals following inhalation exposure to
malathion.