Dental amalgam and urinary mercury concentrations: a descriptive study

BACKGROUND: Dental amalgam is a source of elemental and inorganic mercury. The safety of dental amalgam in individuals remains a controversial issue. Urinary mercury concentrations are used to assess chronic exposure to elemental mercury. At present, there are no indications of mercury-associated adverse effects at levels below 5 μg Hg/g creatinine (Cr) or 7 μg Hg/L (urine). The purpose of the present study is to determine the overall urinary mercury level in the Canadian general population in relation to the number of dental amalgam surfaces. METHODS: Data come from the 2007/09 Canadian Health Measures Survey, which measured urinary mercury concentrations in a nationally representative sample of 5,418 Canadians aged 6–79 years. Urinary mercury concentrations were stratified by sex, age, and number of dental amalgam surfaces. RESULTS: The overall mean urinary mercury concentration varied between 0.12 μg Hg/L and 0.31 μg Hg/L or 0.13 μg Hg/g Cr and 0.40 μg Hg/g Cr. In general, females showed slightly higher mean urinary mercury levels than men. The overall 95(th) percentile was 2.95 μg Hg/L, the 99(th) percentile was 7.34E μg Hg/L, and the 99.9(th) percentile was 17.45 μg Hg/L. Expressed as μg Hg/g Cr, the overall 95(th) percentile was 2.57 μg Hg/g Cr, the 99(th) percentile was 5.65 μg Hg/g Cr, and the 99.9(th) percentiles was 12.14 μg Hg/g Cr. Overall, 98.2% of participants had urinary mercury levels below 7 μg Hg/L and 97.7% had urinary mercury levels below 5 μg Hg/g Cr. All data are estimates for the Canadian population. The estimates followed by the letter “E” should be interpreted with caution due to high sampling variability (coefficient of variation 16.6%-33.3%). CONCLUSIONS: The mean urinary mercury concentrations in the general Canadian population are significantly lower than the values considered to pose any risks for health.