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

MALATHION 156
3. HEALTH EFFECTS
were reported in mouse spermatogonia by Degraeve and Moutschen (1984) and tests for dominant lethal
mutation also were negative in that study. In contrast, Salvadori et al. (1988) reported chromosomal
aberrations in mouse spermatogonia and Hoda et al. (1993) noticed a decrease in meiotic index in primary
spermatocytes of mice treated with malathion. A study in Drosophila also showed a positive dominant
lethal mutation (Kumar et al. 1995).
In general, the results from standard gene mutation tests in bacteria did not show mutagenicity with or
without activation or gave a weak positive response (Pednekar et al. 1987; Shiau et al. 1980; Wong et al.
1989). Results from in vitro studies in mammalian cells, including human lymphocytes, showed that
malathion appeared to produce cytogenetic damage as evidenced by chromosomal aberrations and sister
chromatid exchanges (Balaji and Sasikala 1993; Garry et al. 1990; Nicholas et al. 1979; Nishio and Uyeki
1981; Pluth et al. 1996, 1998; Sobti et al. 1982; Walter et al. 1980). There is weak evidence of in vitro
interaction of DNA bases by malathion (Wiaderkiewicz et al. 1986).
Although it appears that malathion has been tested for genotoxicity in a wide variety of systems, the
results have been mixed largely because of the different experimental designs and different malathion
formulations tested. Studies in vitro should always monitor cell viability to clearly distinguish genetic
effects from cytotoxicity. Also, it would be important to know the composition of the malathion mixture
to be tested and to test each one of the components since humans are likely to be exposed to technical
mixtures rather than to pure malathion. Additional studies are also necessary to examine the interaction
of malathion and DNA. Continued studies on genomic sequence analysis combined with reverse
transcription polymerase chain reaction (PCR) amplification of lymphocytes from malathion exposed
subjects may be able to identify a mutation spectrum that may be fairly specific for malathion and that
could eventually be used as a biomarker of exposure.
Reproductive Toxicity. Limited information was located regarding reproductive effects in humans
following exposure to malathion. A study of pregnant women exposed during periods of malathion
spraying in California found a moderate association between stillbirths and certain exposure variables, but
these associations were not consistent or statistically significant and, therefore, were attributed to chance
(Thomas et al. 1992). An additional study of males involved in the mixing and spraying of a variety of
organophosphates and insecticides found a significantly higher percent of stillbirths and abortions
compared to unexposed couples, and also lower fertility among exposed males (Rupa et al. 1991b).
However, the role of malathion, if any, is impossible to determine. No studies were located on
reproductive effects of malathion in humans exposed orally or dermally.