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

MERCURY 264
2. HEALTH EFFECTS
Animal data support the findings from human studies and provide somewhat more information regarding
lethal exposure levels. Deaths associated with acute-duration inhalation exposure to metallic mercury vapor
have been observed in rats and rabbits at about 27–29 mg/m 3 (Ashe et al. 1953; Livardjani et al. 1991b).
Severe pulmonary edema has been reported as the cause of death following such exposures (Christensen et al.
1937). Severe ataxia occurred prior to death in rats exposed to methylmercury iodide vapor for intermediate
durations (Hunter et al. 1940). Acute oral LD50 values for inorganic mercury ranged from 25.9 to
77.7 mg Hg/kg, with the most sensitive LD50 for 2-week-old rats (Kostial et al. 1978). Increased mortality in
chronic-duration oral studies has been observed at 1.9 mg Hg/kg in male rats gavaged 5 days a week (NTP
1993). Early deaths were attributed to renal toxicity. Oral exposure to methylmercuric compounds has
resulted in increased mortality at 16 mg Hg/kg (single dose) (Yasutake et al. 1991b), 3.1 mg Hg/kg/day for
26 weeks (Mitsumori et al. 1981), and 0.69 mg Hg/kg/day for up to 2 years (Mitsumori et al. 1990).
Systemic Effects
Respiratory Effects. The evidence from case report studies suggests that inhalation of metallic mercury
vapor may result in clinical respiratory symptoms (e.g., chest pains, dyspnea, cough, reduced vital capacity)
(Bluhm et al. 1992a; Gore and Harding 1987; Haddad and Sternberg 1963; Hallee 1969; Kanluen and
Gottlieb 1991; King 1954; Lilis et al. 1985; Matthes et al. 1958; McFarland and Reigel 1978; Milne et al.
1970; Rowens et al. 1991; Snodgrass et al. 1981; Soni et al. 1992; Taueg et al. 1992; Teng and Brennan
1959; Tennant et al. 1961). In the more severe cases, respiratory distress, pulmonary edema, lobar
pneumonia, fibrosis, desquamation of the bronchiolar epithelium, and death due to respiratory failure
have been observed (Campbell 1948; Gore and Harding 1987; Jaffe et al. 1983; Kanluen and Gottlieb
1991; Matthes et al. 1958; Taueg et al. 1992; Teng and Brennan 1959; Tennant et al. 1961). Acute- and
intermediate-duration studies in rabbits appear to corroborate clinical symptoms observed in humans
following inhalation exposure to metallic mercury vapors. Mild-to-moderate pathological changes
(unspecified) were exhibited in the lungs of rabbits exposed to 6–28.8 mg/m 3 mercury vapor for up to
11 weeks (Ashe et al. 1953), and death due to asphyxiation has been observed in rats exposed to 27
mg/m3 for 2 hours (Livardjani et al. 1991b). Lung congestion was observed after 100 hours of continuous
exposure of rats to 1 mg/m3 (Gage 1961). The potential for oral exposure was not quantified; however,
it is likely that most of the exposure was through inhalation. Inconclusive evidence is available regarding
respiratory effects due to inhalation of organic mercury (Brown 1954; Hunter et al. 1940), and there is no
conclusive evidence indicating that oral or dermal exposure to inorganic or organic forms of mercury is