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

MALATHION 84
3. HEALTH EFFECTS
malathion (95% pure) in the diet for 80 weeks (NCI 1978) or 332 mg/kg/day for 103 weeks (NCI 1979a),
or in mice administered up to 2,980 mg/kg/day for 80 weeks (NCI 1978).
Effects in Females. Administration of 827 mg/kg/day malathion (98% pure) to pregnant Sprague-
Dawley rats on Gd 6–13 induced abortions after the 5 th dose, but this dose level also induced lethality
among the dams (Mathews and Devi 1994). A slight but significant decrease in the number of implants
was observed on Gd 20 in Sprague-Dawley rats administered doses of 500 mg/kg/day of malathion
(98% pure) on Gd 6, 10, and 14; this level of malathion exposure also reduced maternal body weight gain
by 22% (Prabhakaran et al. 1993). However, a similar study in which Sprague-Dawley rats were
administered 800 mg/kg/day malathion (94% pure) on Gd 6–15 found no effects on the number of
implantations or resorptions upon examination on Gd 20 (Lochry 1989). A study in rabbits treated with
25, 50, or 100 mg/kg/day malathion (92.4% pure) on Gd 6–18 reported an increase in the number and
percent on resorptions sites/doe at $50 mg/kg/day; there were no effects on fertility, number of corpora
lutea, or implantation sites (Siglin 1985). It should be noted that body weight gain was also decreased at
$50 mg/kg/day. Treatment of female Sprague-Dawley rats with 50 mg/kg/day of malathion (unspecified
purity) for 3 months prior to mating and during Gd 1–20 did not affect the ability to mate or conceive or
the number of total implants or number of implants per dam (Lechner and Abdel-Rahman 1984). No
reproductive toxicity was reported in a 2-generation study in Sprague-Dawley rats (Schroeder 1990). In
this study, male and female rats (F0) were administered 612 and 703 mg/kg/day malathion (94% pure),
respectively, for 63 days before mating, after which time, the rats were mated to produce the F1A litters.
After weaning, F0 rats were mated again to produce the F1B litters. F1B males and females were treated
for 79 days before mating twice to produce F2A and F2B litters. Parameters examined included
reproductive performance, fertility indices, and gestation length.
Limited information exists on the effects of malathion on the histology of female reproductive organs.
An acute study observed disquamation of cells lining the ovary, absence of grafian follicle, distortion of
the uterine epithelium, and enlargement of the tubular uterine glands in Wistar rats that received
approximately 163 mg/kg/day of malathion (unspecified purity) in the diet for 7 days (Ojha et al. 1992);
no significant effects were seen at 18.5 mg/kg/day. An intermediate-duration study reported no
significant histopathological alterations in the ovaries from rats given 10 mg/kg/day of malathion
(94% pure) by gavage for 15 weeks (Ozmen and Akay 1993). In chronic-duration studies, no significant
histopathological alterations were seen in the mammary gland, uterus, or ovaries from rats following
dietary administration of up to 622 mg/kg/day malathion (95%) for 80 weeks (NCI 1978) or
332 mg/kg/day for 103 weeks (NCI 1979a). However, increased incidence of cystic endometrial