EFFECT OF PREPARATION METHODS ON THE ASSESSMENT OF AIRBORNE CONCENTRATIONS OF ASBESTOS FIBRES BY TRANSMISSION ELECTRON MICROSCOPY

Abstract

The usual indirect and direct preparation methods used to assess the airborne asbestos fibre concentrations by transmission electron microscopy (TEM) have been investigated in detail. It has been shown that ultrasonics, often used in the indirect preparation method to facilitate the recovery of dust, may significantly increase the fibre number concentration. This effect is highly variable and dependent on the characteristics of the workplace where the samples were collected. If the indirect preparation method is modified to avoid the use of the ultrasonic treatment, both the direct and indirect preparation methods give comparable results for fibres of length greater than 5 μm. By contrast, the number concentrations of fibres shorter than 5 μm are always different but the reason for this is not clear. Copyright © 1996 BOHS. Published by Elsevier Science Ltd.