[Asbestosis and microfiber role]. / Patologia da asbesto e ruolo delle microfibre.

Based on the predominant content of thin and short asbestos fibres in lung and mesothelioma tissues, it was recently stated (2005) that such fibres "appear to contribute to the causation of human malignant mesothelioma". In another study of the same year it was stated that fibres in the order of few microm length and 0.2 microm diameter are the sole able to induce mesothelioma. This scientific conclusions entail some implications from practical point of view. The enormous amount of information gained on asbestos in the last decades is based on the definition of a fibre as an alongated particle with an aspect-ratio of at least 3:1, a diameter < or = 3 microm and a length > or = 5 microm. These parameters were used up today to define occupational and in some case non-occupational limits. In which way can "reference" values be established if all lengths or only fibres shorter than 5 microm are considered? Nowadays we have no answer. Secondly, assuming a prevalent role of such fibres especially in mesothelioma cases, how can reliable estimates of past exposure obtained in a medico-legal context, since they have never been counted? Morever, how might he the employer responsibility assessed since short fibres were not measured by definition pathogenic, and this not measured, nor were there appropriate filtering systems up to the middle of the '80?

[Asbestos fibres and reference values]. / Fibre di amianto e V.R.

Biological RV for asbestos implies several problems, due to the difficult interpretation of values obtained from various biological samples (sputum, BALF, lung tissue). Therefore, it seems it advisable to refer to environmental concentrations (ERC), which are not avoidable, since asbestos is an ubiquitous contaminant. On the basis of the available studies the 1 f/L value is usually reported as the most representative, although more recent and reliable studies would indicate lower values, at least for outdoor concentrations, as determined by SEM. However, further studies are needed: standardized methods based on SEM (author's opinion) should be adopted; the accuracy of such technique is sufficient for air concentrations from 0.05-0.1 f L-1 upwards, with the advantage of lower costs and time as compared to TEM.