Quantifiable particulate, soluble and even methyl-mercury concentrations are detectable in the Dental waste water (DWW) stream during the removal of amalgam from the oral cavity through aspiration with high vacuum suction. These toxic compounds are discharged into the sanitary sewer system and eventually into the environment, to be taken up by microbes, plants and animals and through the food chain to impact on human mercury consumption. The objectives of this project are to quantify the inorganic and organic concentrations in Dental wastewater, to identify the bacteria in biofilms of the discharge environment and to specifically identify the microbial activities involved in oxidation from metallic Hg(O) to ionic Hg(ll). In addition, other objectives are to determine the reverse reduction enzymatic reaction, the methylation of Hg(lI) to monomethyl-mercury, and finally to specify bacteria responsible for mercury metabolism in DWW biofilms. Specific Aim 1: Analyze mercury concentrations both inorganic and organic in DWW. Hypothesis:Amalgam waste loads correlate to methyl-mercury yields. Specific Aim 2: Classify bacterial species in Dental wastewater lines. Hypothesis: Bacterial species in the Dental sewage pipe biofilms include those from the oral biofilms (e.g. plaque), but more likely are the normal environmental bacteria found growing in other piped water biofilms, from sources not involved with Dental water units. Specific Aim 3: Identify specific bacterial species involved in mercury conversion. Hypothesis: Element mercury released in DWW is converted to Hg(lI) and then in more limited amounts to methyl-mercury by specific biofilm bacterial species in the Dental sewage pipes.