Airborne fibre concentrations in a glass continuous filament factory

Studies of the mortality of workers employed in the glass continuous filament production industry have been completed in an attempt to study any cancer risks in the industry. Exposure measurements made in these factories have shown very low respirable fibre concentrations, some of which were of man-made vitreous fibres (MMVF) although most were of natural non-asbestos mineral fibres. In an attempt further to investigate the exposure in these factories an analytical method based on scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM–EDXS) was developed. The objective of this technique was to enable the various MMVF varieties to be differentiated. The method was applied to samples collected in a glass continuous filament plant. The majority of respirable fibres found on the samples were calcium sulphate, organic fibres, asbestos or glass wool. Thirteen fibres out of 67 analysed had morphology consistent with MMVF. From their compositions, five were almost certainly glass wool but only one of these could possibly have been a glass continuous filament. However, unequivocal identification of this fibre was not possible, because of the wide range in compositions for other man-made mineral fibres. The results of this investigation call into question the ability of any workplace epidemiological study to investigate the potential respiratory cancer hazard from glass continuous filaments.