ELECTRON-MICROSCOPIC ANALYSIS OF AIRBORNE ASBESTOS FIBERS

Scanning and transmission electron microscopic (SEM and TEM) methods for airborne asbestos analysis are reviewed. Electron microscopy has been used since the 1950s to evaluate airborne asbestos size distributions. More recently, methods have been developed to evaluate airborne fiber concentrations in occupational and nonoccupational environments. Developments of recent SEM and TEM methods are presented and discussed. This review focuses on filter preparation, fiber counting, and fiber identification issues. Issues discussed include the type of electron microscope to be used, SEM or TEM; the type of filter media to be used, Nuclepore polycarbonate of membrane filter varieties; and the choice of sample transfer technique, direct or indirect. Due to limited analytical capabilities, SEM methods have received limited use. Standardized TEM analytical methods have been developed, resulting in the routine use of TEM analysis for airborne air samples.