revised final - Agency for Toxic Substances and Disease Registry ...

MERCURY 139
2. HEALTH EFFECTS
Pregnant hamsters that received a single oral gavage dose of mercuric acetate on Gd 8 showed an increase
in the incidence of resorptions at doses as low as 22 mg Hg/kg (Gale 1974). The incidence of resorptions
was 35% at 22 mg Hg/kg, and increases were observed in a dose-related manner (53% at 32 mg Hg/kg,
68% at 47 mg Hg/kg, and 99% at 63 mg Hg/kg).
In a study by Khera (1973), after 5–7 days of oral gavage doses of 1, 2.5, or 5 mg Hg/kg/day as methylmercuric
chloride, male rats were mated to unexposed female rats. A dose-related reduction of mean litter
size was attributed to preimplantation losses from incompatibility of sperm-to-implantation events after
mercury treatment of the parent male rat. At doses of 2 mg Hg/kg/day as methylmercury by gavage during
Gd 6–9, pregnant Sprague-Dawley rats showed no differences in maternal body weight gain before
parturition or in the body weights of the offspring (Fredriksson et al. 1996).
In male mice, no reduction in the incidence of fertile matings was observed after administration of 5–7 oral
doses of up to 5 mg Hg/kg/day as methylmercuric chloride (Khera 1973). There was a significant doserelated
decrease in the number of pups born per litter in mice receiving oral doses of 3, 5, or 10 mg Hg/kg
administered on Gd 8 as methylmercuric hydroxide (Hughes and Annau 1976). Effects were not observed
at 2 mg Hg/kg/day. Similarly, female mice administered 20 mg Hg/kg/day as methylmercuric chloride by
gavage on Gd 10 had increased resorptions, decreased live fetuses per litter, and decreased numbers of
fetuses per litter (Fuyuta et al. 1978). After guinea pigs were exposed to 11.5 mg Hg/kg as methylmercuric
chloride by gavage on Gd 21, 28, 35, 42, or 49, half of the litters were aborted 4–6 days after treatment
(Inouye and Kajiwara 1988). An increased rate of reproductive failure due to decreased conceptions and
increased early abortions and stillbirths occurred in female monkeys exposed to 0.06 or 0.08 mg Hg/kg/day
as methylmercury for 4 months (Burbacher et al. 1988). The menstrual cycle length was not affected at
these dose levels. Reproductive effects were not observed in monkeys exposed to 0.04 mg/kg/day for the
same duration.
Testicular functions were studied in monkeys (M. fascicularis) exposed to 0.025 or 0.035 mg Hg/kg/day as
methylmercury by gavage for 20 weeks (Mohamed et al. 1987). The mean percentage of motile
spermatozoa and the mean sperm speed were significantly decreased for both treatment groups compared to
controls. Morphological examination of semen smears indicated an increased incidence of tail defects
(primarily bent and kinked tails) in both exposed groups. No histopathological effects were evident on the
testes. The study was limited because there were only three animals in each exposure group.