Asbestos disease in foundrymen.

Abstract

To the Editor: The data and information detailed within the report by Scancarello and colleagues1 inadequately support their conclusion that talc and its associated "asbestos" minerals are the sole agents in the etiology of the pleural and interstitial findings among the three foundrymen they studied. Based on the assays provided, we believe that the commercial amphibole asbestos minerals, crocidolite and amosite, and probably chrysotile as well, played the principal role as agents of disease. There are several reasons for our position. First, Scancarello and colleagues report the presence of uncoated crocidolite fibers (case 1) and amosite fibers (cases 2 and 3) in bronchoalveolar lavages (BAL). Although relative exposure intensity and fiber source data are not provided, the minerals are unrelated to talc as an associated ore component. They most certainly cannot be discounted as agents where pleural thickening, pleural plaques, or interstitial markings are found.2 Chrysotile ("serpentine asbestos") was found in the BAL of cases 2 and 3. Although the source of chrysotile is identified as from talc powders, as with amosite and crocidolite the fiber could have just as readily originated from other sources, eg, deteriorating insulation in the workplace. Chrysotile fiber in talc products is most uncommon.3 Second, there is the issue of what has been described to the readership as tremolite asbestos in talc. The names and descriptors tremolite, tremolite asbestos, and amphibole fiber are not synonyms. Their substitutional use throughout the text, especially in view of incomplete mineral assays and characterization, is simply incorrect. In Table 2 of their manuscript, among the analyses shown for commercial talcs, are those offered by Dement and Zumwalde on six New York State talcs.4 The mineral tremolite is noted in Table 2 as asbestos. The tremolite mineral found in this US deposit occurs as the common massive variety, which upon crushing (processing) produces cleavage fragments that crudely resemble asbestos on a morphological basis. The crystallographic distinction between tremolite asbestos and cleavage-fragment is now fully recognized, and their differences in biological activities appreciated by the United States Department of Labor's Occupational Safety and Health Administration as well as other agencies.5 Cleavage fragments have been removed from the US asbestos standard. The criteria used to distinguish asbestos fiber from elongate cleavage fragment has been reviewed by Langer et al.6 Tremolite asbestos has been found to be a carcinogen, whereas tremolite cleavage fragment has not (Davis et al7; Nolan et al8). Furthermore, the data provided in Table 1 of the Scancarello report do not allow any analyst to conclude whether or not the tremolite present in the four talc specimens is asbestiform or not. For that matter, nor are there sufficient data that would allow one to conclude that the tremolite in the BALs was asbestos or not. Last, some commercial talcs may contain amounts of amphiboles, of variable habit, some talc fiber, crystalline silica (quartz) and some host "black wall," which may be made up of the mineral chlorite and/or some serpentine minerals.3 The presence of amphibole asbestos must be substantiated on a crystallographic basis, not merely by chemistry.6 The presence of uncoated fibers of crocidolite, amosite, and chrysotile indicate that other dust sources existed at these worksites. The finding of the amphibole asbestos minerals crocidolite and amosite in the foundrymen's BALs is of enormous importance. It again underscores the occurrence of occult exposure to asbestos-containing products in some workplaces, like foundries, and helps elucidate the problem of agent identification in pleural and parenchymal disease. Arthur M. Langer, PhD; Robert P. Nolan, PhD; Environmental Sciences Laboratory; Brooklyn College; The City University of New York Brooklyn, NY