Mineral fiber content of lungs in patients with mesothelioma seeking compensation in Quebec

Asbestos fibers (AF) and ferruginous bodies (FB) in lung parenchyma from 50 workers seeking compensation from the Workers' Compensation Board of Quebec for pleural or peritoneal mesothelioma were analyzed using transmission electron microscopy (TEM) equipped with energy-dispersive spectrometer (EDS) and phase-contrast microscopy (PCM). These workers had been occupationally exposed in mining and milling activities (12 were from Asbestos Township and 11 from Thetford Mines) and 27 were from other types of industry (asbestos factory, shipyard, etc.). For comparison, analyses of lung tissue at autopsy were done in a group of 49 subjects from a reference population. A 95% confidence interval upper limit of 540 AF < 5 mu m/mg and a 95% confidence interval upper limit 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 of 142 FB/g constituted the upper limit of detectable FB in the lungs of the reference population. Forty-eight of the 50 workers with mesothelioma had either a ferruginous body or total asbestos fiber count greater than the 95% confidence interval for the reference population; the remaining two had amosite and/or crocidolite concentrations greater than the 95% confidence interval for the reference population. The fiber types were different in the three groups, with the lungs of workers from Thetford Mines containing only chrysotile and tremolite, those from Asbestos Township containing chrysotile, tremolite, amosite, and crocidolite, and those in other industries containing largely amosite and crocidolite. We conclude that in this population of workers seeking compensation for mesothelioma, fiber analysis confirmed occupational asbestos exposure in every case. The fiber types responsible for the tumors are probably different in the three different groups.