Generation of Replicate Asbestos Aerosol Samples for Quality Assurance

Abstract

The large numbers of replicate asbestos samples (on the order of 400–600 samples) needed for the Proficiency Analytical Testing (PAT) program, the NIOSH sponsored quality assurance program, have traditionally been prepared by filtering aliquots of liquid asbestos suspensions. This technique has produced samples that are visually nonrepresentative of workplace or environmental asbestos exposure samples. Therefore, an effort was made to develop and carry out a preliminary evaluation of an alternative method for producing these samples using an aerosol generation technique.

A fluidized bed aerosol generator was developed to provide sufficient aerosol to 320 filter samplers at a time. The collection chamber was one already in use for the generation of silica samples. Since the number of samples provided by this system was not sufficient, two sets of samples were combined to produce enough samples for one concentration level for the PAT program. The reproducibility from sample to sample was measured using an image analysis fiber counting system and was found to be quite good (coefficient of variation [C.V.] = 0.14). The interlaboratory C.V. in the PAT program was found to be somewhat better for the aerosol generated samples (C.V. = 0.25) than for those prepared by the traditional approach (C.V. = 0.30–0.32).