[The presence of asbestos on board ships: optical microscopy as a research instrument].

Identification of asbestos in many different kinds of bulk materials was performed by means of optical microscopy and the results are reported in the present paper. Some hundreds of various samples taken aboard ships were analysed: panels, laggings, spray insulations, etc. These analyses were required to be not only reliable but also rapid. The results demonstrated the high reliability as well as the rapidity of the technique. Using both the well-known dispersion staining technique (with central stop objectives or with dark field condensers) and phase-contrast analyses on the same polarizing microscope, we carried out numerous checks on the optical properties of the fibres. Not only were dispersion staining colours detected but also refractive index, elongation and extinction signs, in order to obtain an absolutely certain identification. The Italian laws which deal with the asbestos detection discourage the use of the optical microscope because of its presumed unreliability. This paper tends to demonstrate that Italian laws underestimate the potential of the optical microscope. Optical microscopy is probably the only technique that is reliable, inexpensive and rapid at the same time.