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

MERCURY 186
2. HEALTH EFFECTS
estimated to be 28 and 41 days for a fast and slow phase, respectively (Barregard et al. 1992). Mercury is
excreted in the urine following oral exposure to mercuric sulfide (0.5 mg Hg/kg) (Yeoh et al. 1989).
The overall elimination rate of inorganic mercury from the body is the same as the rate of elimination from
the kidneys, where most of the body burden is localized (see Table 2-4). Inorganic mercury is also readily
cleared from the lung. Elimination from the blood and the brain is thought to be a biphasic process with an
initial rapid phase in which the decline in the body burden is associated with high levels of mercury being
cleared from tissues, followed by a slower phase of mercury clearance from the same tissues (Takahata et
al. 1970). An even longer terminal-elimination phase is also possible because of persistent accumulation of
mercury, primarily in the brain (Takahata et al. 1970). Following a single oral dose of divalent mercury in
10 volunteers, 85% of the 203Hg activity was excreted within 4–5 days, predominantly in the feces (Rahola
et al. 1973).
Following acute mercury vapor intoxication of two humans, it was found that, despite chelation therapy
with multiple chelators (2,3-dimercaptopropanol [BAL] followed by 2,3-dimercaptosuccoinic acid
[DMSA]), relatively high concentrations of mercury remained in the plasma for a very long time (Houeto et
al. 1994). The authors suggested that this could be explained by the progressive release of mercury from
red blood cells and tissues after oxidation. In a group of chloralkali workers exposed to metallic mercury
vapor for 1–24 years (median, 10 years), a decrease in the mercury concentration (following temporary
discontinuation of exposure) in whole blood, plasma, and erythrocytes was found to be best characterized
by a two-compartment model (Sallsten et al. 1993). Using a two-compartment model, half-lives were
estimated, respectively, to be 3.8 and 45 days for the fast and slow phase in whole blood; plasma, 2 and
36 days in plasma, and 3.6 and 16 days in erythrocytes. The half-lives for the slow phases in whole blood
and plasma were longer, and the relative fractions of the slow phases were higher (about 50%) after longterm
exposures than after brief exposures (Sallsten et al. 1993).
Workers exposed to vapors of 0.016–0.68 mg Hg/m 3 had detectable levels of mercury in the urine
(>2 µg Hg/L) (Stopford et al. 1978). Metallic mercury accounted for