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

MERCURY
2.2.1.6 Developmental Effects
2. HEALTH EFFECTS
Metallic Mercury. No association was demonstrated between inhalation exposure of the father and
increased rates of major fetal malformations or serious childhood illnesses in a retrospective cohort study of
workers at a U.S. DOE plant (Alcser et al. 1989).
A case study of a woman chronically exposed to an undetermined concentration of mercury vapor reported
that her first pregnancy resulted in spontaneous abortion, and her second resulted in the death of the
newborn soon after birth (Derobert and Tara 1950). It is unclear whether the reproductive toxicity
experienced by the woman was due to the mercury exposure. However, after recovery from overt mercury
poisoning, she gave birth to a healthy child. A woman occupationally exposed to mercury vapors for
2 years prior to pregnancy and throughout pregnancy was reported to have delivered a viable infant at term
(Melkonian and Baker 1988). Urinary mercury in the woman at 15 weeks of pregnancy was 0.875 mg/L
(normal levels are approximately 0.004 mg/L). Also, a case report of a woman exposed to mercury vapors
in her home during the first 17 weeks of pregnancy reported that the woman delivered a normal child who
met all developmental milestones (although the child was not formally tested for psychological
development) (Thorpe et al. 1992). Although mercury exposure was not measured, the child was born with
hair levels of 3 mg/kg (3 ppm) of mercury. This hair level is comparable to that observed in populations
consuming fish once a week (WHO 1990) and suggests that exposure in this case may have been relatively
low.
Exposure of neonatal rats to metallic mercury vapor at 0.05 mg/m 3 for 1 or 4 hours a day for 1 week during
a period of rapid brain growth (postpartum days 11–17) resulted in subtle behavioral changes when the rats
were tested at 4 and 6 months of age (Fredriksson et al. 1992). Offspring of rats exposed for 1 hour/day
showed increases in the time necessary to finish a task in the radial arm maze (spatial learning). Offspring
of rats exposed for 4 hours a day showed increases in both the time to finish the task and in the number of
errors committed. When tested for locomotor activity at 2 months, an increase in rearing was observed in
the 4 hour/day group, but repeat testing at 4 months showed lower locomotor, rearing, and total activity
than controls. The 1-hour/day exposure group showed no difference from controls at 2 months, and
increased activity and decreased rearing at 4 months when compared to controls.
Three groups of 12 pregnant Sprague-Dawley rats were exposed by inhalation to 1.8 mg/m 3 metallic
mercury vapor on gestation days (Gd) 11–14 and 17–20 for 1 hour ("low dose") or 3 hours ("high dose").
69