Objectif In the directives on classification and labelling of dangerous products, asbestos is a category 1 carcinogen. However, in the absence of a method to quantify asbestos at low levels (e.g. 0,1 %) in a matrix, these has been a delay in implementing the directives to asbestos. To develop an analytical scheme for identification and quantification of asbestos in bulk materials with grain size below 2mm. For typical materials such as quarried rock (e.g. dolomitic marble and granite), minerals (e.g. talc and vermiculite), sediment materials (e.g. clays), and commercial products (e.g. building materials, fillers), the method should obtain, at asbestos levels of 0.1%, results which are with 90% probability correct within a factor of two.No single sample pretreatment method was suitable for the different materials; the approach thus has been to develop a scheme for sample pretreatment consisting of simple modules, each of which were based on existing methods, modified or developed as needed and validated. The scheme begins with a concentration step, chosen according to the type of matrix and asbestos. The residue is exposed to a standard challenge, which is a key concept in the method. It intends by mechanical action to force the material to reveal its potential for release of fibres (hazard). It is obtained in practice by comminution followed by the well-proven dispersion in water using ultrasonic treatment before filtration on the analytical filter. A risk of over-milling was found and a gentle comminution technique was developed for amphiboles. Observation of amphibole fibres on a substrate showed that their cross sections was not square shaped and that they exhibited preferred orientation. Since the PCM method only observes fibre projected width, a correction factor for total fibre volume had to be determined. An improved eye-piece graticule for fibre sizing has been developed. The statistical properties of different counting rules and total fibre volume estimators have been studied and exploited in the development of an efficient counting scheme. Use of fibre number concentration did not have the same discriminating power as the mass concentration, but with calibration for each type of asbestos and matrix it could be used for screening. A method for asbestos identification by PLM has been developed and validated in two interlaboratory comparisons involving 37 EU laboratories. No false negative and only two false positive results were reported. The first draft method for quantification by PCM was used by one project partner on 12 synthetic samples and the target performance was met. The method was tested and improved in a two-step interlaboratory comparison involving 12 laboratories. One very experienced laboratory came close to the target performance, but overall the results were variable across laboratories and individual samples. The results indicate that with care and perhaps considerable practice, it is possible to achieve results approaching the target performance.to develop efficient methods for identification and mass determination of asbestos fibres based on light microscopyto study the effect of sample comminution on fibre size and crystallinity to study the statistical distribution of fibre number and mass concentration measuresto develop an efficient analytical scheme using polarisation (PLM) and phase contrast (PCM) optical microscopy. Champ scientifique agricultural sciencesagriculture, forestry, and fisheriesagriculturegrains and oilseedsnatural sciencesphysical sciencesopticsmicroscopy Programme(s) FP3-MAT - Specific research and technological development programme (EEC) in the field of measurements and testing, 1990-1994 Thème(s) Data not available Appel à propositions Data not available Régime de financement CSC - Cost-sharing contracts Coordinateur NATIONAL INSTITUTE OF OCCUPATIONAL HEALTH Contribution de l’UE Aucune donnée Adresse Lersoe Parkalle 105 KOEPENHAGEN Danemark Voir sur la carte Coût total Aucune donnée
