Document Kz65zgvgGNn5ODnr6DLrXOpNx

American Journal of industrial Medicine 17:525-524 (1990) letter to the editor Re: Mesothelioma in Railroad Machinists Key words: asbestos exposure, mesotbelionia. amphiboles, railroad workers, dirysotile We have read with great interest the report by Or. Mancuso [1988] on the risk of mesothelioma among railroad workers supposedly exposed only to chrysotile. Dr. Mancuso concludes that chrysotile is far more hazardous as an agent of mesothelioma in man than has previously been believed. Indeed, looking at his own numbers, one finds that mesotheliomas accounted for nearly 10% of deaths in his cohort, an ex traordinary figure, and one only previously reported for those heavily exposed to amosite or crocidolite [for example, Selikoff et al., 1979; Jones et al., 1980; and see Table 8.8 in Churg, 1988, for a more complete listing]. Because amphibole in the form of amosite and crocidolite is generally considered to be a much more potent mesothelial carcinogen in man than is chrysotile [Berry, 1986], exposure to these forms of asbestos could greatly affect the mesothelioma incidence in this cohort. The validity of Dr. Mancuso's study thus hinges entirely on the question of whether exposure really was to chrysotile alone. We believe that the data already in the literature, as well as analytical studies (see below) on lung tissue from railroad workers, do not support the idea that these workers were only exposed to chrysotile. Amphiboies were widely used on the railroads in Europe and South Africa [Webster et al., 1977; Mostert and Meintjes, 1979; Ohlson et al., 1984]; and, although there does not appear to be an American study specifically addressing this issue, there is no doubt that amosite and crocidolite were manufactured and sold for use in steam locomotives in the United States [Mc Donald et al., 1982]. Moreover, Dr. Mancuso's own previous report on mesothe lioma among railroad machinists [Mancuso, 1983] notes that amosite was found in 4 of 6 asbestos samples taken from old locomotives, and the present study appears to be based on the same factory and cohort of workers! To examine this issue further, we analyzed the asbestos content of the lung in two long-term railroad workers with pleural mesothelioma (Table I). To our knowledge, these workers did not have any other asbestos exposure. It should be noted that the amosite plus crocidolite values seen in these two individuals are well within the range we have previously found in shipyard workers and insulators with mesothelioma [Churg and Wiggs, 1986]. Obviously, one must draw limited conclusions from two cases, but these data and the literature just cited suggest to us Address reprint requests to Or. Churg. Dept, of Pathology. University of British Columbia, 22! 1 Wesbrook Mall. Vancouver. BC. Canada V6T 2B5 Accepted for publication February 16, 1989. 1990 Wiky-Liss, Inc. 524 TABLE I. Lung Asbestos Content in 2 Railroad Workers With Pleural Mesothelioma Fiber concentratiotvgm dry lung Case-'exposure Case 1: 1922-1971 Case 2: 1937-1974 General population (95th percentile values) from Churg and Wiggs (1986) Amosite 1.500.000 230.000 30,000* Crocidolite 600.000 Chrysotile 2.200.000 140.000 uoo.ooo Tremolite 1.800.000 580.000 1.200.000 `Amosite plus crocidoiiie that amphibole was likely to be present in the cohort studied by Mancuso and prob ably was largely responsible for the mesotheliomas which were observed. Andrew Churg, md, Department of Pathology, University of British Columbia, Vancouver, BC Francis Green, md, Department of Pathology, University of Calgary, Calgary, Alberta REFERENCES Berry G (1986): Chrysotile and mesothelioma. In Wagner JC (ed): "Biological Effects of Chrysolite." Philadelphia: JB Lippincott. pp 123-132. Churg A (1988): Neoplastic asbestos-induced disease. In Churg A. Green FHY (eds): "Pathology of Occupational Lung Disease." New York: Igaku-Shoin Medical Publishers, p 288. Churg A, Wiggs B (1986): Fiber size and number in workers exposed to processed chrysotile asbestos, chrysotile miners, and the general population. Am J Ind Med 9:143-152. Jones JSP. Smith PG. Pooley FD. et al. (1980): The consequences of exposure to asbestos dust in a wartime gas-mask factory. In Wagner JC (ed): "Biological Effects of Mineral Fibres." Lyon: IARC Sci Pub No. 30. pp 637-653. Mancuso TF (1983): Mesothelioma among machinists in railroad and other industries. Am J ind Med 4:501-503. Mancuso TF (1988): Relative risk of mesothelioma among railroad machinists exposed to chrysotile. Am J Ind Med 13:639-657. McDonald AD, Fry JS. Woolley AJ, McDonald JC (1982): Dust exposure and mortality in an American factory using chrysotile. amosste, and crocidolite in mainly textile manufacture. Br J Ind Med 39:368-374. Mostert C. Meintjes R (1979): Asbestosis and mesothelioma on the Rhodesia railways. Cent Afr J Med 25:72-74. Selikoff U. Hammond EC. Seidman H (1979): Mortality experience of insulation workers in the United State and Canada 1943-1976. Ann NY Acad Sci 330:91-116. Webster 1. Cochrane JWC. Solomon A (1977): Pneumoconiosis in non-mining industries on the Witwatersand. S Afr Med J 51:261-264.