An Assessment of Mercury in the Form of Amalgam in Dental Wastewater in the United States

An assessment was conducted of the discharge from dental facilities of mercury in the form of amalgam to surface waters in the United States. Two pathways were examined – effluent from publicly owned treatment works (POTWs) and air emissions from sewage sludge incinerators (SSIs). The annual use of mercury in the form of amalgam in the U.S. is approximately 35.2 tons (31.9 metric tons). It was estimated that 29.7 tons (26.9 metric tons) of mercury in the form of amalgam are annually discharged to the internal wastewater systems of dental facilities during amalgam placements and removals. Based on the partial capture of this amalgam in conventional chair-side traps and vacuum filters, the discharge of mercury in the form of amalgam from dental facilities to POTWs was estimated to be 6.5 tons (5.9 metric tons). The discharge of mercury to surface water via POTW effluents and SSI emissions was estimated to total approximately 0.4 tons (0.4 metric tons). A cost-effectiveness analysis determined that the annual cost to the dental industry to reduce mercury discharges through the use of amalgam separators would range from 380 millionto 1.14 billion per ton.