This report, originally released in September, 1997, presents the results of analyses by the Massachusetts Water Resources Authority ("MWRA"), of wastewatcr from fifteen dental facilities, including three large dental schools, two hospital clinics, one medium-sized clinic, and six small general practice dental offices. Part 1 summarizes the regulatory background for MWRA's concern with mercury. Part 2 presents the results of MWRA's analyses. The report demonstrates that dental discharges are a significant source of mercury. Most of the samples exceeded MWRA's discharge standard of 1 part per billion ("ppb"), ranging as high as 41,400 ppb. The report sets forth MWRA's estimates of dentists' contribution to MWRA's mercury load, using the sample results, MWRA's data on mercury loading at the headworks of its sewage treatment plant, and a range of estimates of the volume of flow from dental facilities. MWRA estimated that dentists contribute at least 10% of MWRA's mercury.
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