Comparison of Phase Contrast and Electron Microscopic Methods for Evaluation of Occupational Asbestos Exposures

Abstract

Abstract Historic air samples collected in the asbestos textile, the friction products, and the cement products industries using chrysotile asbestos during 1964–1971 were analyzed by counting and sizing asbestos fibers by phase contrast optical microscopy and transmission electron microscopy. The proportion of airborne fibers longer than 5 μm in length was found to be significantly different for different industries and operations with a range of 5.0–20.4 percent. Multiple linear regression analyses relating fiber concentrations by phase contrast and electron microscopy methods demonstrated a good correlation for fibers longer than 5 μm. The phase contrast method was found to be a poor predictor of total fiber exposures (all lengths) as measured by transmission electron microscopy. Airborne fibers in the textile industry were found to have longer lengths than those in the cement pipe or the friction products industries. These differences may be important when comparing morbidity and mortality data from different industrial sectors.