Chrysotile, tremolite and fibrogenicity

Recently published analyses have shown that the risks of mesothelioma and l ung cancer in Quebec chrysotile miners and millers mere related to estimate d level of fibrous tremolite in the mines where they had worked, An analysi s has therefore been made of radiographic changes in men who in 1965 mere e mployed by companies in Thetford Mines where the same question could be exa mined for fibrogenicity. Of 294 men who met the necessary requirements, 129 had worked in six centrally located mines, where the tremolite content was thought to be high, 81 in 10 peripheral mines where it was thought to be l ow and 84 in both, The median prevalence of small parenchymal opacities (gr eater than or equal to 1/0) in chest radiographs read by sis readers was hi gher among men ever than never employed in the central mines (13.6% against 7.4%), despite the fact that the mean cumulative exposure was loser in the former (430 mpcf.y vs 520 mpcf.y). After accounting by logistic regression for cigarette smoking, age, smoking-age interaction and cumulative exposur e, the adjusted odds ratio for central mine employment was 2.44 (95% lower bound: 1.06). Together with other surveys of asbestos miners and millers, t his study suggests that amphibole fibres, including tremolite, are more fib rogenic than chrysotile, perhaps to the same extent that they are carcinoge nic, though the data available mere not sufficient to address the latter qu estion. (C) 1999 British Occupational Hygiene Society Published by Elsevier Science Ltd. All rights reserved.