Silvestri, S; Magnani, C; Calisti, R; Bruno, C
The Balangero asbestos mine is the only chrysotile mine in Italy. In this paper, we summarize information on work practice, fiber concentration, and health-related effects in the workers and in the population of the area. Mine activity started in 1917 and grew rapidly during the following years. During the sixties, the number of production lines in the mill increased, and production was between 100,000 and 150,000 tonnes per year. The activity declined during the 1980s and ceased in February 1990. At Balangero, chrysotile asbestos occurs in a serpentinized rock; the percentage of asbestos ranges from 4 to 8%, and fiber length is less than 4-5 mm. The ore also includes balangeroite, a magnesium-iron fibrous silicate similar, from a morphological point of view, to amphibole.
Until the end of the sixties; mining and milling occurred without any reliable system of dust control. Dust control through the ore-treatment process was introduced in 1965 and gradually improved until 1982. The main steps involved filtering, centralized vacuum cleaning, wetting, and the use of air-sealed cabins. Actual measurements of asbestos-fiber concentration date back to 1968, from investigations carried out by technical advisers to the company. A program of periodic and regular dust-monitoring was initiated by the company in 1975 and continued until 1989, with more than 2000 samples collected in 14 years.
The cohort of asbestos miners and millers at the Balangero mine (Piolatto et al. 1990) showed a statistically significant increase in total mortality and in mortality from cancers of the upper aerodigestive tract, pleural malignancies, cardiovascular diseases and liver cirrhosis. Occurrence of pleural malignancies and laryngeal cancers increased with cumulative exposure. We update in this paper the incidence of mesothelioma in the cohort, on the basis of a search of the Literature and of the files of the Mesothelioma Registry of Piedmont. Three additional cases of malignant mesothelioma of the pleura were found with past exposure in the mine, and no evidence of other occupations entailing exposure to asbestos. Cumulative exposure to fibers estimated for these cases was: 340, 319 and 1064 f/mL X years. In the period considered, 0.15 incident cases of pleural mesotheliomas were expected. Frequency of asbestosis in the Balangero workforce also was very high. Piolatto et ai. (1990) observed 16 deaths from asbestosis in 1946-1987, corresponding to a mortality rate of 59 per 100,000 person-years. Fifteen new cases of asbestosis were compensated in 1984-1993 among miners residents in one of the four towns surrounding the mine of Balangero (Ispesl 1997). Three cases of malignant mesothelioma were observed in the general population, but they were explained by occupational or domestic exposure.