Levels of mercury and silver in dust from the trimming of amalgam dies.

The levels of mercury and silver in dust arising from the trimming, i.e. grinding, of amalgam dies in dental laboratories have been measured. In breathing air close to the workpiece, the mercury and silver contents exceeded the threshold limit values for short-term exposure by factors of aboit 60 and 400 in cases when local ventilation was not in use. With efficient local exhaust systems enabling a dust reduction of about 94%, the short-term exposure limit values for mercury and silver were exceeded by factors of about 4 and 20 respectively. Mercury and silver were assayed quantitatively by means of nuclear chemical analysis. A major part of the amalgam dust consisted of respirable particles. The collected dust comprised about 80% amalgam and 20% particulate matter from grinding wheels and stones according to SEM and EDAX measurements.