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

MALATHION 83
3.2.2.5 Reproductive Effects
3. HEALTH EFFECTS
No studies were located regarding reproductive effects in humans following oral exposure to malathion.
Several studies are available that provide information on the reproductive effects of malathion in animals
after oral exposure; most of them have been conducted in rats.
Effects in Males. The effect of malathion on spermatogenesis was examined in juvenile Wistar rats by
Krause et al. (1976). Rats were sacrificed at various times up to the 50 th day of life following two single
gavage doses of 40 mg/kg/day of malathion (unspecified purity) on the 4 th and 5 th day of life, and the
testes were examined. According to the authors, significant findings included a slight reduction in the
number of Sertoli and Leydig cells on the 6 th day, reduction of spermatogonia on days 6 and 12, and
reduction of pachytene spermatocytes on day 18. All abnormalities disappeared by day 50. Seven daily
gavage doses of 20 mg/kg/day of malathion over a 14-day period given to adult male Wistar rats did not
induce any histological alterations in the spermatogenic epithelium and had no significant effect on serum
levels of luteinizing hormone (LH) or testosterone, but increased serum FSH (Krause 1977). A higher
dose of 163 mg/kg/day of malathion (unspecified purity) given mixed in the food for 7 days to Wistar rats
damaged the seminiferous tubules and produced an abnormal pattern of Sertoli cells; no significant
alterations were seen with 18.5 mg/kg/day (Ojha et al. 1992). A considerably higher gavage dose of
1,950 mg/kg of malathion (95% pure) given once to 8-week-old male Wistar rats reduced the number of
germinal layers and produced degeneration and necrosis of gonocytes in the seminiferous tubules during
the first 3 days after dosing (Piramanayagam et al. 1996). These alterations appeared mild by the 6 th day
and almost all tubules showed spermatogenic activity by day 12.
Edema, congestion, and desquamation of lining cells of the seminiferous epithelium were observed in rats
gavaged daily for 12 weeks with 45 mg/kg/day of malathion (unspecified purity) (Balasubramanian et al.
1987a). The same treatment also resulted in lower pH of the seminal fluid, decreased testicular protein,
decrease relative testis weight, decreased activities of testicular LDH, AP, and acid phosphatase, and no
change in AST or ALT activities (Balasubramanian et al. 1987b). Without providing details, the
investigators indicated that all the changes seemed to be at least partially reversible over a 2-week postdosing
period. Wistar rats treated with 390 mg malathion/kg/day (purity unspecified) for 6 weeks had a
reduction in the number of germinal layers in the testes, accumulation of eosinophilic cellular debris in
the lumen of the seminiferous tubules, and intertubular edema (Piramanayagam and Manohar 2002); these
changes appeared reversible after a 6-week post-treatment recovery period. No treatment-related gross or
microscopical alterations were seen in the prostate or testis from rats administered up to 622 mg/kg/day of