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

MERCURY
2. HEALTH EFFECTS
(Langworth et al. 1992b). Similarly, no increases in antilaminin antibodies were observed in workers
exposed for an average of 7.9 years (Bernard et al. 1987), and no increase in antiglomerular basement
membrane antibodies or IgE was seen in workers exposed for between 1.5 and 25 years (Cardenas et al.
1993). Slight decreases in IgA and IgG were observed in workers after more than 20 years of exposure to
metallic mercury vapors when compared to unexposed controls (Moszczynski et al. 1990b). No significant
differences in the concentrations of immunoglobulins or complement components were found in a study of
76 chloralkali workers previously exposed to mercury vapor for an average of 7.9 years (range,
1.1–36.2 years) (Ellingsen et al. 1994). No increase in the prevalence of autoantibodies was observed
between the formerly exposed worker group and a control group of 53 age-matched referents. The average
time elapsed since the cessation of occupational exposure was 12.3 years (range, 1–35 years).
Evidence of a human autoimmune response has been obtained in a few studies. Examination of the kidneys
of two workers with proteinuria revealed granular deposition of IgG and the complement C3 in the
glomeruli (Tubbs et al. 1982). Among a group of 10 patients who reported adverse effects associated with
dental amalgams (the route of exposure is probably a mixture of inhalation exposure to mercury vapor
released from the amalgams and dermal exposure to the amalgams), 3 had increased antiglomerular
basement membrane antibodies and 2 had elevated antinuclear antibodies (Anneroth et al. 1992). After
removal of one amalgam, there was a significant decrease in IgE (it is unknown whether other amalgams
remained). Also, 1 of 89 workers examined by Langworth et al. (1992b) showed a weak reaction to
antiglomerular basement membrane, and 8 of 44 workers examined by Cardenas et al. (1993) showed an
abnormally high anti-DNA antibody titre. Only two studies have shown increases in immune parameters in
exposed populations. Increases in IgA and IgM were observed in workers in a mercury producing plant
(Bencko et al. 1990). The study is limited by a lack of information on daily dose levels, duration of
employment and potential confounding factors (smoking, alcohol). An increase in anti-DNA antibodies
was observed in workers from a chloralkali plant (Cardenas et al. 1993).
Other experimental evidence suggests that mercury can alter a number of parameters of the host's immune
system and lead to increased susceptibility to infections, autoimmune diseases, and allergic manifestations.
In workers exposed to mercury vapor concentrations of 0.024–0.09 mg/m 3 for less than 10 and up to
31 years (Moszczynski et al. 1995), the stimulation of T-lymphocytes (as manifested by an increased
number of T-cells [CD3+], T-helpers [CD4+], and T-suppressors [CD8+]) was observed in peripheral
blood; however, no significant effect was seen on NK-cell (CD16+) count. A positive correlation was
found between the T-helper cell count and the duration of exposure (p