INTERLABORATORY EVALUATION OF THE BREAKUP OF ASBESTOS-CONTAINING DUSTPARTICLES BY ULTRASONIC AGITATION

Measurement of asbestos in settled dust has been suggested as a surrog ate for past and potential future airborne exposures. While conceptual ly appealing, identification and quantitation of those respirable part icles that either were airborne or could become airborne through re-en trainment are complex and difficult tasks: Round robin testing of a dr aft ASTM method [The method has recently been balloted and passed by A STM as Method D-5755.] for determining asbestos in dust was performed to assess the variability of the method and the impact of large, non-r espirable asbestos-containing particles on the reported numerical conc entration of respirable asbestos structures. Tests conducted using sin gle, non-respirable particles of asbestos or asbestos-containing mater ials (ACM) indicate that these large particles can give apparent conce ntrations of asbestos in the dust on the order of millions of structur es per square centimeter. Coefficients of variation (CV) ranged up to 2 for these tests, primarily the result of variable application of the indirect preparation procedure. A second series of tests was conducte d using simulated building dusts. ACM dust was blown throughout a cont rolled chamber, and the resulting settled dust was sampled and distrib uted to participating laboratories. These results indicate that the in terlaboratory CV is similar to that of the first tests, but can be red uced to 0.8 if restrictions are placed on the indirect sample preparat ion procedure. There was no statistically significant difference in th e concentration of asbestos collected from three different surfaces, b ut this is the result of limited data and highly variable results. Ove rall, these tests indicate that the analysis of surface dusts using in direct sample preparation should be limited to qualitative evaluation as to the presence of asbestos in the surface dust.