MINERAL FIBER CONTENT OF LUNGS IN PATIENTS WITH MESOTHELIOMA SEEKING COMPENSATION IN QUEBEC

Asbestos fibers (AF) and ferruginous bodies (FB) in lung parenchyma fr om 50 workers seeking compensation from the Workers' Compensation Boar d of Quebec for pleural or peritoneal mesothelioma were analyzed using transmission electron microscopy (TEM) equipped with energy-dispersiv e spectrometer (EDS) and phase-contrast microscopy (PCM). These worker s had been occupationally exposed in mining and milling activities (12 were from Asbestos Township and 11 from Thetford Mines) and 27 were f rom other types of industry (asbestos factory, shipyard, etc.). For co mparison, analyses of lung tissue at autopsy were done in a group of 4 9 subjects from a reference population. A 95% confidence interval uppe r limit of 540 AF < 5 mu m/mg and a 95% confidence interval upper limi t of 161 AF greater than or equal to 5 mu m/mg dried lung tissue were found for the reference population. Similarly, a concentration of FB o f 142 FB/g constituted the upper limit of detectable FB in the lungs o f the reference population. Forty-eight of the 50 workers with mesothe lioma had either a ferruginous body or total asbestos fiber count grea ter than the 95% confidence interval for the reference population; the remaining two had amosite and/or crocidolite concentrations greater t han the 95% confidence interval for the reference population. The fibe r types were different in the three groups, with the lungs of workers from Thetford Mines containing only chrysotile and tremolite, those fr om Asbestos Township containing chrysotile, tremolite, amosite, and cr ocidolite, and those in other industries containing largely amosite an d crocidolite. We conclude that in this population of workers seeking compensation for mesothelioma, fiber analysis confirmed occupational a sbestos exposure in every case. The fiber types responsible for the tu mors are probably different in the three different groups.