Interlaboratory Evaluation of the Breakup of Asbestos-Containing Dust Particles by Ultrasonic Agitation

Measurement of asbestos in settled dust has been suggested as a surrogate for past and potential future airborne exposures. While conceptually appealing, identification and quantitation of those respirable particles that either were airborne or could become airborne through re-entrainment are complex and difficult tasks. Round robin testing of a draft ASTM method [The method has recently been balloted and passed by ASTM as Method D-5755.] for determining asbestos in dust was performed to assess the vari ability of the method and the impact of large, non-respirable asbestos-containing particles on the reported numerical concentration of respirable asbestos structures. Tests conducted using single, non-respirable particles of asbestos or asbestos-containing materials (ACM) indicate that these large particles can give apparent concentrations of asbestos in the dust on the order of millions of structures 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 conducted using simulated building dusts. ACM dust was blown throughout a controlled chamber, and the resulting settled dust was sampled and distributed to participating laboratories. These results indicate that the interlaboratory CV is similar to that of the first tests, but can be reduced to 0.8 if restrictions are placed on the indirect sample preparation procedure. There was no statistically significant difference in the concentration of asbestos collected from three different surfaces, but this is the result of limited data and highly variable results. Overall, these tests indicate that the analysis of surface dusts using indirect sample preparation should be limited to qualitative evaluation as to the presence of asbestos in the surface dust.