A MONTE-CARLO ASSESSMENT OF MERCURY EXPOSURE AND RISKS FROM DENTAL AMALGAM

Dental amalgam is approximately 50% mercury (Hg) by weight, and person s bearing amalgam fillings are exposed to this element, primarily as H g vapor. For Canadians with amalgam-filled teeth, it was estimated, ba sed on two independent models, that Hg exposure from amalgam averaged: 0.045 to 0.082 mu g/kg bw/day in toddlers (aged 3 to 4 years); 0.044 to 0.069 mu g/kg bw/day in children (aged 5 to 11 years); 0.034 to 0.0 44 mu g/kg bw/day in teens (aged 12 to 19 years); 0.050 to 0.055 mu g/ kg bw/day in adults (aged 20 to 59 years); and 0.031 to 0.041 mu g/kg bw/day in seniors (aged 60+ years). Amalgam was estimated to contribut e, on average, 50% of total Hg exposure from all sources (amalgam, air ,water, food, soil) in adults, and 32 to 42% for other age groups. Num erous studies have consistently reported effects on the central nervou s system (CNS) in persons occupationally exposed to Hg vapor. Most suc h studies have failed to detect a threshold for the CNS effects measur ed. A tolerable daily intake (TDI) of 0.014 mu g Hg/kg body weight/day (as an absorbed dose) was proposed for inhalation of mercury vapor, t he principal form of Hg to which bearers of amalgam fillings are expos ed. This TDI was based on a published account of subclinical tie., not resulting in overt symptoms or medical care) CNS effects in occupatio nally-exposed men, expressed as slight tremor of the forearm, and shou ld also protect against cognitive function impairment. Based on the le ast conservative exposure model of the two independent models develope d, the average numbers of amalgam-filled teeth estimated not to compro mise the TDI were: 1 filling in toddlers; 1 filling in children; 3 fil lings in teens; and 4 fillings in adults and seniors.