Comparison of a Wipe Method With and Without a Rinse to Recover Wall Losses in Closed Face 37-mm Cassettes used for Sampling Lead Dust Particulates
Closed-face 37-mm polystyrene cassettes are often used for exposure monitoring of metal particulates. Several methods have been proposed to account for the wall loss in air sampling cassettes, including rinsing, wiping, within-cassette dissolution, and an internal capsule fused to the filter that could be digested with the filter. Until internal capsules replace filters, other methods for assessing wall losses may be considered. To determine if rinsing and wiping or wiping alone is adequate to determine wall losses on cassettes, we collected 54 full-shift area air samples at a battery recycling facility. We collected six replicate samples at three locations within the facility for three consecutive days. The wall losses of three replicate cassettes from each day-location were analyzed following a rinse and two consecutive wipes. The wall losses of the other three replicates from each day-location were analyzed following two consecutive wipes only. Mixed-cellulose ester membrane filter, rinse, and wipes were analyzed separately following NIOSH Method 7303. We found an average of 29% (range: 8–54%) recovered lead from the cassette walls for all samples. We also found that rinsing prior to wiping the interior cassette walls did not substantially improve recovery of wall losses compared to wiping alone. A rinse plus one wipe recovered on average 23% (range: 13–33%) of the lead, while one wipe alone recovered on average 21% (range: 16–22%). Similarly, we determined that a second wipe did not provide substantial additional recovery of lead (average: 4%, range: 0.4–19%) compared to the first wipe disregarding the rinse (average: 18%, range: 4–39%). We concluded that when an internal capsule is not used, wall losses of lead dust in air sampling cassettes can be adequately recovered by wiping the internal wall surfaces of the cassette with a single wipe.