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

MERCURY 349
2. HEALTH EFFECTS
from multiple sources (i.e., organic mercury from fish consumption in conjunction with metallic mercury
released from dental amalgam).
Epidemiological and Human Dosimetry Studies. There have been a number of occupational
studies on workers chronically exposed to metallic mercury vapors. Mercury exposure (as measured by
urine or blood mercury levels) and neurological effects have been evaluated (Adams et al. 1983; Miller et
al. 1975; Roels et al. 1982; Smith et al. 1970). The most obvious deficiency in these epidemiological
studies is the absence of good measures of exposure. Additional data are needed on the potential health
effects for populations near hazardous waste sites based upon specific identification of the form of mercury
and the pathways of exposure (i.e., the levels of exposure that populations near waste sites may actually
experience from inorganic mercury in the air, water, and soil, or methylmercury in contaminated food).
An area of considerable controversy, which is in need of good epidemiological data, is the potential for
adverse effects from the mercury released from dental amalgam. Although this is not an exposure pathway
associated with hazardous waste sites, mercury from amalgam represents a major contributor to the total
body burden for a large percentage of the population, and thus must be factored into an assessment of the
toxicokinetic behavior and toxic effects of mercury originating from a waste site. Long term longitudinal
studies are needed for all dose durations and forms to evaluate delayed or persistent expression of mercury
toxicity.
Biomarkers of Exposure and Effect
Exposure. Blood and urine mercury levels have been used as biomarkers of high level exposure in acute
and chronic studies for both inorganic and organic mercury (Akesson et al. 1991; Naleway et al. 1991;
Verschoor et al. 1988). Hair has been used as a biomarker for chronic low level organic mercury exposure
(Nielsen and Andersen 1991a, 1991b; Oskarsson et al. 1990), with an awareness of the potential for
external contamination (Clarkson et al. 1983). Further development of more sensitive tests to measure
mercury in expired air and retention in hair are needed for monitoring short- and long-term exposures,
respectively, for populations at risk.
As seen in other studies comparing European to Japanese hair mercury levels, the hair levels reported by
Nakagawa (1995) of 2–4 ppm for a Japanese population are 10–20 times higher than levels observed in the
Drasch et al. (1997) study (median, 0.247 µg/g in hair; range, 0.43–2.5 µg/g). These differences in the
mercury exposure may affect not only the mercury hair levels but also the mercury hair-to-tissue