"BACKGROUND Among asbestos substitute fibres, man-made organic fibres (MMOFs) are currently being put to interesting uses in industrial applications. These fibres are classified by the International Agency for Research on Cancer (IARC) as Group 3: unclassifiable as to carcinogenicity in humans.OBJECTIVES The objective of this study is to provide a comprehensive review of the toxicity of some MMOFs currently used as asbestos substitute material and to prepare an analytical reference catalogue that would allow to identify these fibres in commercially available materials.METHODS The diameters of 100 fibres each of polyacrylonitrile (PAN), polyvinyl alcohol (PVA), polyethylene (PE) and aramids were measured by scanning electron microscopy. Each material was analyzed by diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) and X-ray diffractometry (XRD).RESULTSThe four materials examined for the purposes of this study were found to be non-respirable due to their geometric characteristics, since their average diameters were calculated at 10.5 ?Ìm for PAN, 14.20 ?Ìm for PVA, 20.5 ?Ìm for PE and 11.7 ?Ìm for aramid fibres. Only aramid fibres, which may produce fibrils of respirable size when subjected to abrasion or other types of stress, were found to have fibrils with a diameter of less than 1 ?Ìm. For this reason, high priority was given by the IARC and the World Health Organisation (WHO) to re-evaluate the hazards of these fibres. In conclusion, DRIFT spectra and the diffractograms of the four materials examined here are presented and discussed."

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