[The preparation and characterization of fine dusts carried out in the Clinica del Lavoro di Milano in support of experimental studies].

This paper aims to illustrate the conditions selected at the Clinica del Lavoro of the University of Milan to prepare and analyze a large number of fine dust samples produced over a period of about 50 years, that were initially used for studies within the Clinic performed in its own facilities, and since 1956 were sent to other Italian and overseas laboratories (Luxembourg, UK, Germany, Norway, Sweden, South Korea, USA). The total quantity of material distributed (with maximum size 7-10 microns) was about 2 kg and consisted of the following mineral and artificial compounds: quartz, HF-treated quartz, tridymite, HF-treated tridymite, cristobalite, chromite, anthracite, quartz sand for foundry moulds, sand from the Lybian desert, vitreous silica, pumice, cement, as well small quantities of metallic oxides, organic resins, chrysotile, crocidolite, fibres (vitreous, cotton and polyamidic). About half of the entire quantity of dusts produced consisted of partially HF-treated tridymite.

[Optical and electron microscopic methods for counting respirable fibers of asbestos: considerations on relative standards].

The paper reports experience of the use of optical and electronic microscope methods for assessment of the concentration of airborne asbestos fibres and their respective identification. The results described are derived from the extensive experience of three Italian university institutes, which have used optical methods of observation for over 35 years (phase contrast technique, at times associated with the use of polarized light) and have examined altogether about 11,000 samples of airborne dust and fibres. After considering in more detail certain values of asbestos fibre concentrations in various environments, measured parallely with optical and electronic microscope, and assessing their basic comparability, attention is drawn to a number of ambiguities and contradictions contained in Law D.

[Diffractometric analysis of non-pulverized coherent materials].

The paper presents an initial series of results of diffractometric assays, carried out by directing an X-ray beam on glossy sections of coherent, rigid materials (asbestos-cement blocks, insulation panels, ceramic tiles). The study, which is an introduction to another concerning crystalline rocks, is aimed at assessing the possibility of increasing the diffracted intensities, using samples with high mass concentration, avoiding the consequences of loss of crystallinity following extremely fine grinding, which is considerable especially when compounds having very different mechanical resistance and elastic modulus are simultaneously present. The assays carried out demonstrated the validity of the method for qualitative analysis, whereas in quantitative terms the diffracted intensities were mainly increased (up to 40%), but not in a manner directly connected with the type and macro- and microscopic structure of the compounds under study.