Evaluation of chemical releases and worker exposures from filter press operations

The exposures (inhalation and dermal) and releases (air, water, solids, and process streams) associated with the filtration of industrial wastewater sludge from an electronics manufacturing plant were characterized. Chemical releases and worker exposures for a target chemical (total copper) were measured over four operational cycles. Various aspects of the filtration operation believed to influence the measurement values were documented. Worker exposures associated with the discreet stages of the filter operation were measured. Ventilation patterns around the filter press were also monitored. The workers' time-weighted average exposures to total copper during the 113-minute operational cycle ranged from 3.1 to 25 micrograms/m3 (2.2 geometric standard deviation, 6.4 micrograms/m3 geometric mean concentration). The manual removal of filter cake comprised only 15% of the time in an average filtration cycle, but produced 72% of the workers' inhalation exposure. During this cake-removal stage, inhalation exposures ranged from 11 micrograms/m3 to 130 micrograms/m3 (2.5 geometric standard deviation, 30 micrograms/m3 geometric mean concentration). Differences in worker technique may account for the large range of inhalation exposures during the cake-removal stage. Exposures and releases were successfully determined for a single unit operation, as well as for the discreet stages of operation. The data generated will enable EPA to more accurately estimate worker exposures and chemical releases for new chemicals as required by the Toxic Substances Control Act. The approach utilized will benefit industrial hygienists in providing estimates of worker exposures and aid in the targeting of survey sampling.