An experiment to develop conversion factors to standardise measurements of airborne asbestos.

Various researchers and agencies recommend different conversion factors for different asbestos exposures. The aim of this study was to develop conversion factors from particles per cm3 (p cm(-3)) to fibres per cm3 (f cm(-3)) and from mg m(-3) to f cm(-3). More than 1000 exposure measurements were available in the Slovenian asbestos-cement factory Salonit Anhovo. Three types of measurement of asbestos concentrations in the air were used: a konimeter measuring p cm-3, a gravimetric method measuring mg m-3 and a membrane filter method measuring f cm-3. Operation-specific conversion factors among these methods were developed. One conversion factor was obtained for asbestos-pipe-dry jobs (4.7) and one for asbestos-sheet-dry jobs (1.6). Only one conversion factor (0.8) was used for asbestos-cement-pipe-wet and asbestos-cement-pipe-dry jobs. For asbestos cement sheets, two conversion factors were obtained (0.3 and 1.2). The development of five different conversion factors made it possible to calculate cumulative exposure to asbestos from historical data and to decrease exposure misclassification.