Asbestos Cement
Mixed exposures to chrysotile and amphiboles are reported in asbestos cement manufacturing, and some mesothelioma cases are found among the workers. In Lithuania, a study was done of cancer incidence and cause-specific deaths among workers in two asbestos cement factories. Accessing cancer registry records, 1 case of pleural mesothelioma was observed with 0.3 expected, which was "noninformative concerning asbestos exposure and mesothelioma risk," according to the researchers. One factory started operations in 1956 and the other in 1963, and both factories have only used almost 600,000 tons of raw chrysotile asbestos that was imported from the Sverdlovsk region of Russia (Smailyte et al., 2004). A lung tissue study of workers after occupational and environmental exposure to asbestos in the Russian chrysotile industry rebuts the assumption that asbestos from Russia is only chrysotile, showing that about 5% of all mineral fibers were amphiboles (Tossavainen et al., 2000). A small group of Italian women who worked in the asbestos-cement industry, mainly exposed to crocidolite, and subsequently compensated for asbestosis, had 18 deaths reportedly due to mesothelioma (Germani et al., 1999).
In Ontario, mortality was investigated among 535 asbestosexposed and 205 nonexposed employees of a factory manufacturing asbestos cement pipe, asbestos cement board, and rockwool insulation materials in separate sheds. Raw materials for the pipe included cement, silica, and chrysotile and crocidolite asbestos; in the board manufacturing operation only chrysotile was used. Personal air sampling for production workers was done after 1969, and the cohort exposure average was 60 f/ml-yr. There were 21 deaths from mesothelioma in the cohort (19 confirmed pathologically), with 17 in production workers. The expected number of mesothelioma deaths for the cohort was 4. All of the men dying of mesothelioma were exposed to both crocidolite and chrysotile asbestos in the pipe plant (Finkelstein, 1984). A Swedish cohort of manufacturing workers was studied for exposures to chrysotile primarily (>95%), but also smaller amounts of amphiboles. Thirteen pleural mesothelioma cases were observed among 2898 workers (22,000 person-years) having a cumulative exposure of 13 f/ml-yr when followed for an average of 62 years (Albin et al., 199Oa). A cohort of workers employed during 1950 to 1981 in Vocklabruck, Austria, the oldest asbestos cement factory in the world, was exposed primarily to chrysotile. Crocidolite was used in the pipe factory from 1920 to 1977. Five of 540 deaths were due to mesothelioma among 2816 workers (51,000 person-years) with 25 f/ml-yr cumulative exposure, but all were associated with the use of crocidolite in pipe production (Neuberger and Kundi, 1990). At a factory in Belgium, a cohort study having over 29,000 person-years of follow-up found one mesothelioma. Exposures were up to 3,200 f/ml-yrs during the timeframe of the study, but the authors state that their estimates might be inaccurate by 10-fold. Although 90% of the asbestos by weight used at this facility was chrysotile, the remainder was crocidolite and amosite (Lacquet etal., 1980).
Asbestos cement manufacturing plants in New Orleans that predominately used chrysotile asbestos have been studied, and asbestos content in most products ranged from 15% to 28%. Plant 1 added amosite ( 1 % of product) and infrequently used crocidolite in the manufacture of corrugated bulkhead, and facilities in Plant 2 used crocidolite steadily, which constituted 3% of the pipe material (Weill et al., 1979). Among 6931 workers exposed to mixed fibers, 9 mesotheliomas in Plants 1 and 2 were found (Hughes et al., 1987; Hodgson and Darnton, 2001). In a study of asbestos cement factory in Wales, two mesotheliomas were reported, but both were exposed to crocidolite (Thomas et al., 1982). Eighteen mesothelioma cases were found among 541 workers in the asbestos cement industry in Norway, where 8% amphiboles were added to the chrysotile used (Ulvestad et al., 2002). For Danish workers in the asbestos cement industry between 1928 and 1984, 13 cases of mesothelioma were observed. For pleural cancer among the male workers, the observed/expected rate was statistically elevated at 5.46, but amphiboles were used starting in 1946 (Raffn et al., 1989). From Poland there is a report of 5 mesotheliomas among 3563 male workers (Szeszenia-Dabrowska et al., 1997), and 21 mesotheliomas were found among Israeli workers using 90% chrysotile and 10% crocidolite mixture to produce asbestos cement products (Tulchinsky et al., 1999). The mortality study of 1506 workers of a French asbestos cement factory at Paray-Le-Monial who were employed at least 5 years (providing nearly 34,000 personyears) observed 4 mesotheliomas, 1 of which was a peritoneal case with a latency period of 13.5 years. The 3 deaths from pleural mesothelioma had an average latency of less than 25 years, resulting in a mean of 22.4 years. Founded in 1940, this factory used not only chrysotile but also crocidolite (Alies-Patin and Valleron, 1985).