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

MERCURY 449
5. POTENTIAL FOR HUMAN EXPOSURE
(15.2 ppm) were from Nome, Alaska where the population consumes large amounts of fish and marine
mammals (Lasora and Citterman 1991) and from Florida (15.6 ppm), where measurements were made only
in adults that consumed wildlife from the Everglades area, a region where high mercury levels in wildlife
have been reported (Fleming et al. 1995). Most recently, Davidson et al. (1998) reported the results of the
Seychelles Child Development Study at 66 months (5.5 years) post-parturition. These researchers reported
that there were no adverse neurodevelopmental outcomes observed in mother-child pairs, with mean
maternal and mean child hair total mercury concentrations of 6.8 ppm and 6.5 ppm, respectively, in the
Seychelles Island study.
Oral Tissues. Mercury concentrations as high as 380 µg/g (ppm) have been found in oral tissues in
contact with amalgam fillings. In individuals with more than six amalgam fillings, a mean value of 2.3 µg/g
(ppm) was found in tissue without direct contact with amalgam fillings (Björkman et al. 1997). In some
European countries, health authorities recommend that sensitive or susceptible individuals in higher risk
groups (i.e., pregnant women and individuals with kidney disease) avoid treatment with dental amalgam
(Björkman et al. 1997).
Occupational Exposure. Workplace environments presenting the largest potential sources of
occupational exposure to mercury include chloralkali production facilities, cinnabar mining and processing
operations, and industrial facilities involved in the manufacture and/or use of instruments containing liquid
mercury (Stokinger 1981). According to NIOSH (1973), the principal route of occupational exposure to
mercury is vapor phase inhalation from workplace atmospheres. Studies by Barregard et al. (1992) and by
Langworth et al. (1992b) revealed increased total mercury levels in blood and urine of exposed chloralkali
workers. These results are summarized in Table 5-19. Personal air sampling of workers in a mercury
recycling plant in Germany showed mercury levels ranging from 115 to 454 µg/m 3 (Schaller et al. 1991).
Human tissues that are routinely monitored as evidence of exposure to mercury are urine, blood, and hair.
Urine is most frequently monitored as an indicator of human body burden following chronic exposure to
mercury vapor, particularly in occupational settings; approximately 95% of all urine samples contain less
than 20 µg /L (ppb) (EPA 1984b). A comparison of mercury content in the urine of Swedish workers
exposed to high levels of mercury, dentists, occupationally unexposed workers, and unexposed workers
without dental amalgams gave values of 15, 1.7, 0.8, and 0.3 µmol/mol creatinine, respectively
(corresponding mercury plasma levels were 35, 9.4, 5.3, and 2.8 nmol/L [7.19, 1.89, 1.06, and 0.56 ppt],
respectively) (Molin et al. 1991). Blood and urine monitoring may be useful for groups of workers subject