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

MERCURY 351
2. HEALTH EFFECTS
conducted at 6-month intervals. Workers new to these industries would be the best subjects, since their
pre-exposure blood and urine levels could be used as reference values.
A biomarker/exposure could also be conducted in persons with dental amalgam fillings. Urine levels
should be tracked in those with fillings and in those with removed or replaced amalgam fillings. There are
a number of confounding factors and logistical difficulties in conducting such studies, and new study
protocols should be developed to address the problems encountered in previous studies.
Effect. Potential biomarkers of effect for mercury-induced renal toxicity have been well described
(Cardenas et al. 1993; Lauwerys et al. 1983; Rosenman et al. 1986; Verschoor et al. 1988). Biomarkers for
neurological changes (e.g., paresthesia, decreased motor function, and impaired nerve conduction) have
also been described (Clarkson et al. 1976; Shapiro et al. 1982). There is long history of evaluation of the
neurophysiological and neuropsychological effects associated with mercury levels in blood, urine, and
(Levine et al. 1982; Vroom and Greer 1972; Williamson et al. 1982). More recently, studies are evaluating
cognitive and neurobehavioral effects with increasing sophistication in the assays and analyses that are
used (Davidson et al. 1998; Grandjean et al. 1997b, 1998). Additional biomarkers are needed in this
continuing effort to resolve subtle cognitive or neurobehavioral effects, and immune system effects from
chronic low level exposures to methylmercury in food or metallic mercury released from dental amalgam,
especially in sensitive populations.
Absorption, Distribution, Metabolism, and Excretion. Limited data are available to assess the
relative rate and extent of absorption in humans following inhalation exposure to metallic mercury
(Barregard et al. 1992; Berlin et al. 1969; Friberg and Vostal 1972; Hursh et al. 1976; Teisinger and
Fiserova-Bergerova 1965) and in humans and animals following oral exposure to both inorganic salts and
organic mercury (Aberg et al. 1969; Clarkson 1971, 1972a, 1989; Endo et al. 1989, 1990; Fitzhugh et al.
1950; Friberg and Nordberg 1973; Kostial et al. 1978; Miettinen 1973; Nielsen 1992; Nielsen and
Andersen 1992; Rice 1989b; Suzuki et al. 1992; Urano et al. 1990; Weiss et al. 1973; Yeoh et al. 1989).
Indirect evidence of absorption following inhalation exposure in humans and animals is reported for
inorganic and organic mercury (Clarkson 1989; Ostlund 1969; Warfvinge et al. 1992; Yoshida et al. 1990,
1992). Only limited quantitative data were located regarding dermal uptake of metallic mercury in humans
(Hursh et al. 1989). Information is needed regarding the rate and extent of dermal absorption of inorganic
and organic mercury in humans and animals. Quantitative information concerning the inhalation and oral
absorption of mercury (all forms)are needed.