Mercury levels and discharge in waste water from dental clinics

Data was obtained on the amount of Hg discharged with the waste water from dental clinics. Waste water from 20 Danish dental clinics was collected during one working day and analyzed for the total amount of Hg using the technique of cold vapour atomic absorption spectrophotometry (CVAAS). From clinics without amalgam separator mean value was 270 mg Hg dentist(-1) d(-1) (range 65 to 842), from clinics equipped with amalgam separator mean value was 35 mg Hg dentist(-1) d(-1) (range 12 to 99). It was concluded that Hg is released with the waste water from dental clinics. Several hundred grams of Hg clinic(-1) may be discharged annually with the waste water. Installation of efficient amalgam separators may reduce the Hg outlet markedly.