engleski

Evidence of asbestos fibers in the materials

OBJECTIVE: The purpose of the study was to provide the evidence of asbestos by form and presence in the different types of materials, as to be contribution to the medical criteria for restriction of work with asbestos materials. National Institute for Occupational Health and Safety (NIOSH) stated: &laquo ; all levels of asbestos exposure studied to date demonstrated asbestos-related diseases&raquo ; and &laquo ; there is no level of exposure below which clinical effects do not occur&raquo ; . New legislation in European Community and the United Nations Environment Programme (UNEP) states that all forms of asbestos should be banned and added to an international list of chemicals submitted to trade controls. MATERIALS AND METHODS: The six asbestos reference standards have been prepared and validated by Institute of Occupational Medicine, UK on behalf of Health and Safety Executive, UK. They are intended to be used as reference samples in the analysis of types of asbestos in bulk material. Each asbestos sample displays faithful properties by polarized light microscopy, electron microscopy, X-ray diffraction and infrared spectrophotometry. The samples are therefore representative of typical asbestos types of the amphibole and serpentine minerals. The identification of commonly encountered asbestos fibers can be performed with a dispersion staining objective using five high dispersion liquids having the refraction index (RI) values 1.550 for chrysotile, 1.605 for tremolite and anthophylite, 1.640 for actinolite, 1.670 for amosite and 1.700 for crocidolite. A protocol for routine identification of asbestos types in materials by polarizing light microscopy, asbestos reference standards and dispersion stain method has been offered within the program “ Asbestos In Materials Scheme (AIMS)” under the guide of Health and Safety Committee on Fibre Measurement at Health and Safety Laboratory (HSL), Sheffield, United Kingdom. AIMS include identification of asbestos in unknown materials that are sent by HSL. So far, eight samples of such materials were processed at Institute for Medical Research and Occupational Health in Zagreb. RESULTS: Chrysotile asbestos is used in a large variety of products, from textiles to lagging materials. Amosite asbestos is typical to see in lagging material. Crocidolite asbestos exhibits strong pleochroism from blue-gray to deep blue color. Tremolite asbestos is colorless and non-pleochroic under light microscopy. Actinolite asbestos exhibits pale green to bluish green and slightly pleochroic appearance under light microscopy. Anthophyllite asbestos appears in gray-white color. On examination by light microscopy anthophyllite fibers are colorless and non-pleochroic. CONCLUSIONS: The various forms of asbestos exhibit distinctive optical properties, most notably RI. Being crystalline materials, each form has more than one RI. For routine purposes the examinations by means of polarized light microscopy (PLM) are usually sufficient to identify positively whether asbestos is present and its type. Certificate issued by HSE Committee on Fibre Measurement, United Kingdom, provides Laboratory competence for analyzing and identification of asbestos in materials.

asbestos; polarized light microscopy; chrysotile; tremolite; anthophylite; actinolite; amosite; crocidolit; dispersion staining

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