Estimation of environmental mercury emissions from dental amalgam restorations into the environment: retrospective cross-sectional study

Objectives: Mercury is a major environmental pollutant that when ingested causes nervous system and kidney damage.Dental amalgam is a major mercury-containing product with a mercury content of approximately 50%; however, there has been a lack of systematic studies in Korea on the agespecific distribution of amalgam-filled teeth, and on the resulting environmental emissions.Methods: Dental panoramic radiographs of 756 patients taken at the Y Dental Clinic in Daegu were analyzed to investigate the amalgam filling rate, prosthetic restoration rate, and number of teeth filled, by age group.Atmospheric and soil mercury emissions from amalgam-filled teeth were estimated using the 2016 Statistics Korea death statistics (n=247,900), cremation rate (80.8%), and burial rate (19.2%).Calculations were based on the assumptions that the percentages of amalgam restorations beneath prosthetic restorations were 0%, 30%, 50%, 70%, and 100%.Geometric means and 95% confidence intervals were calculated using SPSS v20.0.The study was approved by Yeungnam University IRB (YU 2017-02-001).Results: Of the 756 participants, 53% had amalgam restorations and 82% had prosthetic restorations.The geometric mean number of amalgam-filled teeth was highest in the 40-49 years age group (4.80), and the number of prosthetic restorations increased with age.Estimated annual mercury emissions ranged from 24,260 g to 123,630 g, depending on the assumed percentage of amalgam beneath prosthetic restorations.Under the clinically plausible moderate scenario (50% amalgam under prostheses), total emissions were estimated to be 73,946 g, including 61,035 g from cremations and 12,911 g from burials.Conclusions: Dental amalgam in deceased individuals releases substantial amounts of mercury, predominantly via cremations.Clinical preburial removal of amalgam restorations and installation of mercury filtration systems in crematoria could be considered as potential measures to mitigate environmental and public health risks.