Assessment of Mercury Exposure and Risks from Dental Amalgam

For Canadians with amalgam-filled teeth, it was estimated that total mercury (Hg) exposure averages: 3.3 µg Hg/day in toddlers (aged 3 to 4 years); 5.6 µg Hg/day in children (aged 5 to 11 years); 6.7 µg Hg/day in teens (aged 12 to 19 years); 9.4 µg Hg/day in adults (aged 20 to 59 years); and 6.8 µg Hg/day in seniors (aged 60+ years). Of this exposure, amalgam was estimated to contribute 50% to total Hg exposure in adults, and 32 to 42% for other age groups. Estimates, based on two independent models, of exposure from amalgam alone were: 0.8-1.4 µg Hg/day in toddlers; 1.1-1.7 µg Hg/day in children; 1.9-2.5 µg Hg/day in teens; 3.4-3.7 µg Hg/day in adults; and 2.1-2.8 µg Hg/day in seniors. There are insufficient published data on the potential health effects of dental amalgam specifically to support or refute the diverse variety of health effects attributed to it. Numerous studies constantly report effects on the central nervous system (CNS) in persons occupationally exposed to Hg. Virtually all studies failed to detect a threshold for the effects CNS measured. A tolerable daily intake (TDI) of 0.014 µg Hg/kg body weight/day was proposed for mercury vapour, the principal form of mercury to which bearers of amalgam fillings are exposed. This TDI was based on a published account of sub-clinical (i.e. not resulting in overt symptoms or medical care) CNS effects in occupationally exposed men, expressed as slight tremor of the forearm. An uncertainty factor of 100 was applied to these data, to derive a reference dose (TDI) which should, in all probability, prevent the occurrence of CNS effects in non-occupationally-exposed individuals bearing amalgam fillings. The number of amalgam-filled teeth, for each age group, estimated to cause exposure equivalent to the TDI were: 1 filling in toddlers; 1 filling in children; 3 fillings in teens; and 4 fillings in adults and seniors. It was recognized that filling size and location (occlusal versus lingual or buccal) may also contribute to exposure. However, data suggest that no improvement in prediction of exposure is offered by any particular measure of amalgam load. Therefore, the estimates of exposure derived from the number of filled teeth were considered as reliable as those that might be based on size and position of amalgam fillings, were such data available for the Canadian population. Effects caused by allergic hypersensitivity to amalgam or mercury, including possible auto-immune reactions, can …