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

MERCURY 273
2. HEALTH EFFECTS
daily subcutaneous doses of methylmercuric chloride showed slight increases in thyroid weight and basal
levels of thyroid-stimulating hormone and thyroxine (Kabuto 1991). However, it was unclear whether these
changes were statistically significant. In contrast, a single subcutaneous dose of 6.4 mg/Hg as methyl-
mercuric chloride resulted in significant decreases in serum thyroxine (Kabuto 1987). At higher doses
(9.6 and 12.8 mg mercury), increases in prolactin and thyroid-stimulating hormone were observed. The
reason for these differences is unclear, but the data suggest that thyroid function may be affected if persons
are exposed to sufficiently high concentrations of mercury.
Animal studies also provide evidence of mercury-induced effects on the corticosteroid levels. Increased
adrenal and plasma corticosterone levels were reported in rats receiving 2.6 mg Hg/kg/day as mercuric
chloride in drinking water after 120 days (Agrawal and Chansouria 1989). At 180 days of exposure, these
effects were not evident in the animals. The investigators suggested that mercuric chloride is a dose- and
duration-dependent chemical stressor. Subchronic administration of methylmercury to rats caused a
diminished secretory response of corticosterone and testosterone serum levels following adrenocorticotropin
(ACTH) and human chorionic gonadotropin (HCG) stimulation, respectively (Burton and Meikle 1980). The
adrenal glands showed marked hyperplasia and increased weight, and basal levels of these hormones were
also depressed. The treated animals exhibited stress intolerance and decreased sexual activity. These results
suggest that methylmercury may have an adverse effect on steroidogenesis in the adrenal cortex and testes.
Based on these animal studies, inorganic and organic mercury may also act on the corticosteroid system to
alter hormonal levels. It is unclear to what extent the effects observed are the result of generalized stress or
direct toxic effects on the endocrine system regulating corticosteroid levels.
Inhalation of metallic mercury vapor may result in a metal fume fever-like syndrome characterized by fatigue,
fever, chills, cough, and an elevated leukocyte count (Bluhm et al. 1992a; Garnier et al. 1981; Lilis et al.
1985; McFarland and Reigel 1978; Milne et al. 1970; Schwartz et al. 1992; Snodgrass et al. 1981). Also,
children with acrodynia frequently exhibit low-grade intermittent fevers (Aronow et al. 1990; Warkany and
Hubbard 1953). Animal data are not available to support this finding, but the human data suggest that
exposure to sufficiently high concentrations of metallic mercury vapor may result in transient fever (see
Hematological Effects).
Immunological Effects. As indicated in the section on dermal effects, allergic dermatological reactions
occurred in persons exposed to inorganic mercury from dental amalgams, tattoos, or breakage of medical
instruments (Anneroth et al. 1992; Bagley et al. 1987; Biro and Klein 1967; Faria and Freitas