Identification and counting of asbestos fibers.
Taylor DG; Baron PA; Shulman SA; Carter JW
Am Ind Hyg Assoc J 1984 Feb; 45(2):84-88
A method for the identification and counting of airborne asbestos (1332214) fibers was tested. It involved the phase contrast count procedure corrected for non asbestos fiber count using an analytical electron microscope (AM) procedure. Twenty replicate filter samples were prepared using laboratory aerosol generated samples containing amosite (12172735) and wollastonite (13983170) fibers. The filters were cut in half. One half was used for optical counting, and the other half was used for AM analysis. Total fiber content was determined by a modified phase contrast microscopic count method, and the AM procedure was added to identify the fraction of amosite asbestos fibers present. This fraction then was applied to the routine optical counts of all the samples in the set to estimate the asbestos fiber concentration. The optical counts gave a mean concentration of 4.06 fibers per milliliter with a relative standard deviation (SD) of 15.7 percent. Variances occurred between samples, between wedges from the same sample, and within wedges, but about 66 percent of the variation was due to sample to sample variability. The mean concentration by the AM method was 3.67 fibers per milliliter with a SD of 25.5 percent. Most of the variation was due to the AM counting process. Variabilities also occurred in the fiber elemental ratios of identifying amphibole or serpentine diffraction patterns. The AM count method achieved a precision of 20.1 percent SD with a bias of minus 9.1 percent compared with the optical count procedure. Routine AM analysis was more labor intensive and required much more time than the optical count alone. The authors conclude that more research is needed to analyze variables contributing to errors in the determination of airborne asbestos fiber concentrations.
NIOSH-Author; Respirable-dust; Asbestos-fibers; Airborne-fibers; Fibrous-dusts; Air-monitoring; Sampling-methods; Industrial-hygiene; Air-filters; Quantitative-analysis
1332-21-4; 12172-73-5; 13983-17-0
American Industrial Hygiene Association Journal