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

MERCURY 118
2. HEALTH EFFECTS
group sizes were small, survival data were not reported, and a considerable number of early deaths from
pneumonia were noted.
Endocrine Effects
Inorganic Mercury. No studies were located regarding endocrine effects in humans after oral exposure to
inorganic mercury.
Several studies have reported effects on the thyroid after acute- or intermediate-duration exposure to
mercuric chloride. An increase in iodine release from the thyroid was observed following gavage
administration of 7.4 mg Hg/kg/day as mercuric chloride to rats for 6 days (Goldman and Blackburn 1979).
Serum levels of thyroid hormones (triiodothyronine and/or thyroxine) in mice decreased after administration
of 6 mg Hg/kg/day as mercuric chloride or mercuric sulfide for 10 days by gavage (Sin et al. 1990). Similar
effects were observed after 4 weeks of dosing with mercuric sulfide (Sin and The 1992). Administration by
gavage of 5.3 mg Hg/kg/day as mercuric chloride to rats for 40 days resulted in increased thyroid weight,
thyroidal iodine uptake, and protein-bound iodine in the serum (Goldman and Blackburn 1979). Decreased
triiodothyronine and monoiodotyrosine were also observed. Dietary exposure of rats to 2.2 mg Hg/kg/day as
mercuric chloride for 3 months resulted in decreased thyroidal iodine uptake, release, and turnover (Goldman
and Blackburn 1979). Adrenocortical function was evaluated in male rats exposed to 0, 9, 18, or
36 mg Hg/kg/day as mercuric chloride in drinking water for 60–180 days (Agrawal and Chansouria 1989).
A significant increase in adrenal and plasma corticosterone levels in all dose groups was observed after
120 days of exposure. After 180 days of exposure, corticosterone levels had returned to control values. The
relative adrenal gland weight was significantly increased for all exposed groups compared to control values.
In a 4-week range-finding study, groups of 5 rats per sex (10 per sex for controls) received diets containing
mercuric chloride at 5, 10, or 20 mg Hg/kg/day in males and 5.5, 11.1, and 22.2 mg Hg/kg/day in females.
The high dose resulted in an increased relative adrenal weight in males and a decreased absolute adrenal
weight in females (Jonker et al. 1993b)
Organic Mercury. No studies were located regarding endocrine effects in humans or animals after oral
exposure to organic mercury.