Objective: The objective of this study was to measure total mercury and methyl mercury from a 12 chair dental clinic. Methods: Specimens were collected from a 15 gallon trap located downstream from the dental clinic and before discharge into the sewer system. The trap was drained and samples collected every 24 hours, allowed to settle 24 hours and then aliquots taken from the supernatant and the sediment. A new analytical technique for inorganic mercury and methyl mercury developed in the Department of Natural Resources and Environmental Sciences at UIUC was used. Solid sediment and supernatant samples were microwave digested for 3 minutes at 200W in 10 ml of an aqueous acidic solution with an added mercury-complexing ligand and then centrifuged. One in five samples was spiked with methyl mercury for recovery calculations. Extractant solutions were passed over an ion-exchange resin to trap charged methyl and inorganic mercury complexes and separate them from the matrix solution and then eluted with potassium bromide for injection into the liquid chromatography system. Metal complex chromatography was used to separate inorganic and methyl mercury species, which were then quantified by an on-line flow-injection cold-vapor generation system coupled to an atomic fluorescence system. Mercury contents were measured by fluorescence generated of Hg (valence 0) gas on a Tekran 2500 atomic fluorescence detector and peak areas of the chromatograms integrated by PeakSimple software. Results: The preliminary data indicates a methyl mercury level of 3ppb for the supernatant portion and 400 ppb for the sediment portion and 300-320 ppm for total mercury in the sediment of the dental wastewater samples. Conclusions: The dental waste stream has the potential to generate significant amounts of methyl mercury from the sediment from dental clinic wastewater. Supported by NIDCR grant DE14777.

Back to the Dental Materials: VII - Others-Metallic Program
Back to the IADR/AADR/CADR 82nd General Session (March 10-13, 2004)

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