Cadmium Exposures at Three Nonferrous Foundries: An Unexpected Trace Source

Abstract

Trace substances are often ignored as a potential source of significant occupational exposures. Trace substances include intermediates, byproducts, natural components, or a minor additive. An unexpected finding from a lead exposure assessment at a brass foundry was the identification of cadmium in one of the samples. Cadmium exposure was unexpected since it was not listed on the available documents (e.g., MSDS) and its presence was unknown to foundry representatives. Cadmium was found to be a trace component (maximum of 0.003%) in special high-grade (SHG) zinc added to molten brass or bronze alloys. Employees using as little as four pounds of SHG zinc containing 0.0004% cadmium had exposures that exceeded the Occupational Safety and Health Administration's 2.5 μg/m3 action level and 5 μg/m3 permissible exposure limit. Cadmium exposures at the three nonferrous foundries in this study were variable but, in general, metal pourers had the highest exposures (up to 7.2 μg/m3), followed by finishing workers (up to 1.9 μg/m3), and then furnace operators (up to 1.6 μg/m3). A pourer's exposure during a 3-min metal pouring cycle was 34.4 μg/m3. Air samples taken in the plume emitted after adding one pound (454 g) of zinc to the molten metal contained high cadmium levels (up to 3070 μg/m3) demonstrating zinc was the cadmium source. This study shows that the trace cadmium in SHG zinc can result in overexposures when used for brass and bronze alloying and trace components must be considered when evaluating potential employee exposures.