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

MERCURY 172
2. HEALTH EFFECTS
The longest retention of mercury after inhalation of mercury vapor occurs in the brain (Takahata et al.
1970). Japanese workers who died 10 years after their last exposure to metallic mercury vapors still had
high residual levels of mercury in their brains (Takahata et al. 1970). Autopsies of 3 dentists revealed
0.945–2.110 mg Hg/kg in the renal cortex, compared to 0.021–0.810 mg Hg/kg for unexposed controls
(Nylander et al. 1989).
In volunteers who inhaled a tracer dose of metallic mercury vapor for 20 minutes, approximately 2% of the
absorbed dose was deposited per liter of whole blood after the initial distribution was complete (Cherian et
al. 1978). Uptake into the red blood cells was complete after 2 hours, but plasma uptake was not complete
until after 24 hours. Mercury concentration in red blood cells was twice that measured in the plasma. This
ratio persisted for at least 6 days after exposure. However, the ratios of 1–2 have been reported for metallic
mercury vapor (Miettinen 1973).
Exposure of rats to mercury vapor (10–100 µg/m 3 ) for 6 hours a day, 5 days a week from the 4th through
11th weeks of life resulted in measurable amounts of mercury in the blood, hair, teeth, kidneys, brain,
lungs, liver, spleen, and tongue, with the kidney cortex having the highest mercury concentration (Eide and
Wesenberg 1993). Further, tissue concentrations were positively and significantly correlated with exposure
concentrations. In this study, the rat molars were found to have the highest correlation coefficient with
measured kidney mercury values, leading to a suggestion by the authors that human deciduous teeth may be
useful indicators of chronic mercury exposure and of the mercury uptake by the kidneys and cerebrum
(Eide and Wesenberg 1993). In another study, a 4-hour exposure of mice to metallic mercury vapor
produced the highest mercury retention in the brain compared to other organs (Berlin et al. 1966).
Exposure of mice to metallic mercury vapor (8 mg/m 3 , for 6 hours a day for 10 days) resulted in higher
mercury levels in the gray than in the white brain matter (Cassano et al. 1966, 1969). Exposure of rats to
1 mg/m3 metallic mercury vapor for 24 hours a day every day for 5 weeks or 6 hours a day, 3 days a week
for 5 weeks resulted in mean mercury brain concentrations of 5.03 and 0.71 µg/g, respectively (Warfvinge
et al. 1992). Mercury was found primarily in the neocortex, basal nuclei, and the cerebellar Purkinje cells.
Mercury also accumulates in several cell types populating the dorsal root ganglia (Schionning et al. 1991).
After 12–14 hours of exposure of rats to a relatively small amount of metallic mercury vapor (0.55 mg/m3 ),
accumulation of mercury was observed within all cell types examined (ganglion cells, satellite cells,
fibroblasts, and macrophages). Mercury has also been detected in dorsal root neurons and satellite cells of