Urinary mercury level in Japanese school children: influence of dental amalgam fillings and fish eating habits.

The influence of dental amalgam fillings and fish eating frequency on the urinary mercury (Hg) level was evaluated in 1642 children (ages: 3-18) living in Tokyo. Geometric mean of the urinary Hg level was 1.9 microgram Hg/l and 1.9 micrograms Hg/g creatinine (Cr) for boys and 2.1 micrograms Hg/l and 2.0 micrograms Hg/g Cr for girls. Multiple regression analysis was conducted using: (1) urinary Cr concentration (only in the case of urinary Hg expressed as microgram Hg/l); (2) age; (3) gender; (4) number of dental amalgam fillings; and (5) fish eating frequency as independent variables. As a result, all the variables examined were significant and the explanatory powers (square of multiple correlation coefficient) of these variables were 17 or 7% for urinary Hg expressed as microgram Hg/l or microgram Hg/g Cr, respectively. Number of dental amalgam fillings or fish eating frequency explained only up to 1.5% of the total variance of urinary Hg. Contribution of Cr concentration, age and gender to urinary Hg level is also discussed.