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

MALATHION 145
3. HEALTH EFFECTS
(Prabhakaran and Devi 1993). In a study of similar design, the same group of investigators reported that a
low protein diet plus malathion may have induced more severe embryotoxicity in rats than either
treatment alone, but it is difficult to draw a definite conclusion from the data presented in the study
(Prabhakaran et al. 1993).
3.10 POPULATIONS THAT ARE UNUSUALLY SUSCEPTIBLE
A susceptible population will exhibit a different or enhanced response to Malathion than will most
persons exposed to the same level of malathion in the environment. Reasons may include genetic
makeup, age, health and nutritional status, and exposure to other toxic substances (e.g., cigarette smoke).
These parameters result in reduced detoxification or excretion of malathion, or compromised function of
organs affected by malathion. Populations who are at greater risk due to their unusually high exposure to
malathion are discussed in Section 6.7, Populations With Potentially High Exposures.
Some of the most common signs and symptoms of organophosphate intoxication are bronchoconstriction
and increased bronchial secretions; therefore, individuals with respiratory conditions such as asthma may
be affected by exposure to malathion levels lower than would affect normal subjects. However, following
aerial application of malathion in Santa Clara County, California, in 1981, a survey conducted to assess
the acute health effects of the application found no significant increase in the number of asthma-related
visits to a university medical school in the area; however, the authors cautioned that the numbers in the
study may have been too small to provide definite conclusions (Kahn et al. 1992).
Anticholinergic agents have been recommended for the treatment of wide variety of conditions, but
therapeutic uses have been established mainly in four areas: atony of the smooth muscle and the intestinal
tract and urinary bladder, glaucoma, myasthenia gravis, and termination of the effects of competitive
neuromuscular blocking agents (Taylor 1996). Any individual using anticholinergic agents for
therapeutic purposes may be at risk of suffering an increase in unwanted side effects due to possible
addition of effects if exposed to organophosphate pesticides.
Little information was located regarding possible polymorphism in enzymes involved in the metabolism
or toxic actions of malathion. Talcott et al. (1982) evaluated malathion carboxylesterase activity in
143 human blood serum samples and found an activity range that spanned almost two orders of
magnitude (0.1–7.2 units/mL), but found no remarkable age-, sex-, or race-related activity differences.
Without providing further details, Abou-Donia (1995) indicated that a genetically determined low level of