by Cynthia Welland September 1991
SQG-DENTAL-1b(9/91)
Objective
The Municipality of Metropolitan Seattle conducted a study October-December 1990 to:
- identify toxic contaminants discharged to Metro's sanitary sewerage system from dental offices
- determine the impact of metals - particularly mercury - in dental waste on the Metro sewerage system
- develop waste management program recommendations
Metro conducted the study as part of its Industrial Waste Small Quantity Generator Program. The study was also done in preparation for the implementation of the Local Hazardous Waste Plan for King County.
Background
Metro selected the waste stream of dental offices for study because of the high use of mercury, silver and other metals in dental work. Mercury is of special concern to Metro because of occasional treatment plant discharge violations caused by mercury spikes at the Renton and West Point treatment plants.
Methodology
To characterize the waste stream, Metro analyzed samples from volunteer dental offices for metals. Local dentists were surveyed to assess their attitudes, behavior and knowledge of waste management practices. The survey also provided information about quantities of spent photographic fixer and dental amalgam waste.
>Results
- Most of the samples exceeded Metro's local discharge limits for mercury, silver and copper.
- About 14 percent of the mercury loading to the Metro sewerage system appears to come from dental offices.
- Because small volumes of mercury come from individual offices, it is very unlikely that dental office waste is the source of mercury spikes observed at the Renton and West Point treatment plants.
- The survey indicates that the dental profession has a high level of interest in proper waste management.
Recommendations
Based on the survey and analytical results, Metro should develop and implement a program requiring a significant reduction in the amount of waste discharged from dental offices to the sewerage system. This program should:
- promote recycling of materials now being taken to solid waste landfills
- encourage the involvement of the local dental association in producing and transmitting clean, concise guidelines for waste management
- coordinate with other governmental agencies in addressing and avoiding unclear or conflicting information
- incorporate waste management guidelines in the formal education of dentists and dental assistants
- require that spent photographic fixer be recycled or reclaimed
- require a reduction in the amount of mercury discharged from the dental operatory waste stream.
- explore mechanisms, such as filtration, settling and centrifuging, to control mercury entering the sewerage system
- evaluate the effectiveness of the waste management guidelines.
|
