An industrial hygiene field study of dental laboratories in the greater Salt Lake area.

An industrial hygiene study of thirteen dental laboratories in the greater Salt Lake area was performed in order to characterize the typical personal occupational exposures to hazardous substances in these workplaces. Full-shift personal air samples were collected for nickel, chromium, cobalt, beryllium, and free silica during the grinding and polishing of non-precious metal and porcelain dental restorations. Short-term personal and area samples for beryllium fumes were also taken during the metal casting process. Personal samples were collected for methyl methacrylate vapors generated during the preparation of acrylic dentures. The results of the air sampling were compared to the threshold limit values and permissible exposure levels for these substances. Most of the air samples indicated low or non-detectable time-weighted average concentrations of the metals and free silica. However, three high exposures to beryllium (>1.5 um-g/m3) and one high exposure to cobalt dust (>160 um-g/m3) were measured in two of the laboratories during the grinding and polishing of non-precious metal. The samples taken during the casing process also indicated low or non-detectable levels of beryllium fumes. Very low (<1.7 ppm) time-weighted average concentrations of methyl methacrylate were detected in the samples collected during the preparation of dentures. Ventilation measurements were taken at these laboratories and recommendations have been made in consideration of the other factors that appear to affect exposure patterns in these workplaces. The potential for significant overexposures to hazardous substances in dental laboratories does exist; however, exposure levels to these materials apparently can be minimized with the utilization of proper ventilation design and work practices.