Workplace validation of a laboratory evaluation test of samplers for inhalable and "total" dust

Parallel personal breathing zone sampling of dust with the IOM sampler and the open-face 37 mm filter cassette has been performed at seven plants wher e dusting processes take place indoors. The particle size distribution in t he breathing zone and the amount of dust collected by passive sampling was also determined. The prevailing orientation of the worker in relation to th e dust source was noted. Measured ratios of dust concentrations sampled wit h the open-face 37 mm filter cassette and the IOM sampler were compared wit h estimated ratios of dust concentrations obtained from the sampled size di stributions and published sampling efficiencies of the two samplers determi ned in a wind-tunnel experiment. The results of the workplace sampling show that at these plants the inhalable size distribution often contained very coarse particles and that the maximum air speed was low, generally less tha n 0.3 m s(-1). The worker mainly faced and handled the predominant dust sou rce. The comparison of the sampled and estimated dust concentration ratios of the open-face 37 mm filter cassette to the IOM sampler showed that the r atio of sampled dust concentrations were 25% lower than estimated. The pres ent test method employed for dust samplers in wind-tunnels may therefore be improved in order to be even more valid for workplace sampling. The cause of the deviation between the workplace and the wind-tunnel could not be fou nd, but the following major differences between the two cases are probably involved: bias in sampling efficiency between electrically insulating and c onducting IOM samplers, lower air speed at workplaces than in wind-tunnel e xperiments, workers handling the source, dust concentration gradients betwe en the collarbone and the lapel. (C) 1999 Elsevier science Ltd. All rights reserved.