[First intercalibration test of diffractometric measurements of asbestos in National Italian laboratories]

The Ministry of Health established by law (D.M. 14/5/96) minimum requirements for laboratories intending to perform asbestos analyses, and identified the central facilities that are to coordinate the future quality control programme (based on the kind of techniques used), to which the laboratories must refer in order to continue to operate in the "asbestos" field. Before initiating the quality control programme for the gravimetric technique based on X-ray diffraction measurement, the central facilities decided to carry out a pilot test in a group of sample laboratories in order to assess the current situation in Italy and identify the main problems involved in implementing the programme. In fact, up to the present, no standardized method for the diffractometric measurement of asbestos exists in Italy, so that the various laboratories use different procedures and reference standards. In the pilot test, a group of 15 national laboratories with proven experience performed diffractometric measurements on 3 samples each containing one of the 3 commercial forms of asbestos (chrysotile, crocidolite and amosite). Besides the final result consisting of the percentage by weight compared to the whole sample, information was requested on the measurement procedure and on the reference standards used. The results, although they do not permit definite conclusions to be drawn due to their small number, do provide information that will be of relevance to the organisation of the future quality control programme. Analysis of the data appear to show that neither the measurement procedure used nor the type of asbestos influence the accuracy of the results. The main source of variability and of deviation from the true values seemed instead to depend on the type of standards used and on compatibility, in terms of particle size and comminution technique, between these standards and the samples analyzed.