Particle size characterizations of copper and zinc oxide exposures of employees working in a nonferrous foundry using cascade impactors

This study characterized exposures to copper and zinc oxide as respirable o r nonrespirable using personal impacters and compared the results with prev ious findings obtained using cyclones. Twenty-five sets of air samples were taken over a 10-month period using single jet cascade impacters. Five to s ix stages were used to capture and classify aerosols according to their aer odynamic diameter (d(ae)). These ranged from <0.5 mu m to >10 mu m d(ae). T wenty-two air samples were taken on employees casting brass alloys, and thr ee samples were taken in areas in the vicinity where employees routinely wo rked. Twenty one air samples were taken during the casting of a single bras s alloy (containing 70% copper and 30% zinc), and the remaining samples wer e obtained from employees casting two different brass allays: a nearly pure copper alloy and a nickel-copper alloy. The results indicated that 55-96% (by mass) of all copper aerosols collected had a d(ae) greater than or equa l to 10 mu m. More than 85% (by mass) of all copper exposures were estimate d as nonrespirable using the current ACGIH-CEN-ISO definition. Zinc oxide a erosols were collected at all stages of the impacters, with significant amo unts found to have a d(ae) greater than or equal to 10 mu m. More than 60% (by mass) of all zinc oxide exposures were estimated to be nonrespirable. A comparison of data collected using impacters and cyclones demonstrated tha t cyclones could be used to differentiate larger aerosol particles from fum es, rather than requiring the use of impacters. It is recommended that appr opriate particle size selective sampling methods be used to classify exposu res of metals to dusts and fumes.