This study characterized exposures to copper and zinc oxide as respirable or nonrespirable using personal impactors and compared the results with previous findings obtained using cyclones. Twenty-five sets of air samples were taken over a 10-month period using single jet cascade impactors. Five to six stages were used to capture and classify aerosols according to their aerodynamic diameter (d(ae)). These ranged from < 0.5 microm to > 10 microm d(ae). Twenty-two air samples were taken on employees casting brass alloys, and three samples were taken in areas in the vicinity where employees routinely worked. Twenty-one air samples were taken during the casting of a single brass alloy (containing 70% copper and 30% zinc), and the remaining samples were obtained from employees casting two different brass alloys: 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) > or = 10 microm. More than 85% (by mass) of all copper exposures were estimated as nonrespirable using the current ACGIH-CEN-ISO definition. Zinc oxide aerosols were collected at all stages of the impactors, with significant amounts found to have a d(ae) > or = 10 microm. More than 60% (by mass) of all zinc oxide exposures were estimated to be nonrespirable. A comparison of data collected using impactors and cyclones demonstrated that cyclones could be used to differentiate larger aerosol particles from fumes, rather than requiring the use of impactors. It is recommended that appropriate particle size selective sampling methods be used to classify exposures of metals to dusts and fumes.

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