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

MALATHION 85
3. HEALTH EFFECTS
hyperplasia was seen in B6C3F1 mice administered 1,490 mg/kg/day malathion (95% pure) for 80 weeks
(NCI 1978).
The highest NOAEL values and all reliable LOAEL values for reproductive effects in each species and
duration category are recorded in Table 3-2 and plotted in Figure 3-2.
3.2.2.6 Developmental Effects
No studies were located regarding developmental effects in humans following oral exposure to malathion.
The developmental toxicity of malathion has been investigated primarily in rats, although some
information is also available in mice and rabbits.
Embryotoxicity. In acute studies in rats, embryotoxicity was evident only in a study by Prabhakaran et al.
(1993) who reported a reduction in the number of live fetuses per litter and reduced fetal weight in
Sprague-Dawley rats treated with 500 mg/kg/day (only level tested) malathion (98% pure) on Gd 6, 10,
and 14. It should be noted, however, that treated dams gained significantly less weight during pregnancy
than controls. No embryotoxicity was observed in Wistar rats treated with 100 mg/kg/day malathion
(unspecified purity) on Gd 6–15 (Khera et al. 1978) or in Sprague Dawley rats treated with
800 mg/kg/day malathion (94% pure) also on Gd 6–15 (Lochry 1989). Reduced fetal weight and crownrump
length were seen in mice gavaged once on Gd 6 with 125 mg/kg malathion (unspecified purity) and
examined on Gd 15; however, no information was provided on maternal effects (Asmatullah et al. 1993).
Two studies in rabbits provided no evidence of embryotoxicity following gavage administration of
100 mg/kg/day malathion on Gd 7–12 (Machin and McBride 1989a) or Gd 6–18 (Siglin 1985).
Increased neonatal mortality (days 7 and 21 after birth) was reported in Wistar rats following maternal
exposure to 240 mg/kg/day malathion (95% pure) in the diet for at least 5 months starting before mating
(Kalow and Marton 1961). It is unclear, however, whether the rats were exposed during gestation.
Furthermore, no information was provided regarding maternal effects. Schroeder (1990) conducted a
2-generation study in Sprague-Dawley rats in which the animals were administered malathion (94% pure)
in the diet at various levels between 43 and 703 mg malathion/kg/day. The only developmental effect
noticed was a decrease in body weight gain in pups from the F1A and F2B litter during the lactation
period at parental doses of 394 mg/kg/day for males and 451 mg/kg/day for females. The corresponding
NOAELs were 131 and 153 mg/kg/day. In this study, there were no significant effects on clinical signs,
growth before mating, food consumption, or maternal weight gain during gestation.