Retention of Asbestos Fibers in Lungs of Workers with Asbestosis

The following research was conducted by Dufresne A, Bégin R, Massé S, Dufresne CM, Loosereewanich P, Perrault G., from McGill University, Department of Occupational Health, Faculty of Medicine, Montréal, Québec, Canada.

OBJECTIVE: To conduct a mineralogical study on the particles retained in the necropsied lungs of a homogenous group of asbestos miners and millers from Asbestos township (and a local reference population) and to consider the hypothesis that there is a difference in size between fibers retained in the lungs of patients with asbestosis with and without lung cancer.

METHODS: Samples of lung tissue were obtained from 38 patients with asbestosis without lung cancer, 25 with asbestosis and lung cancer, and 12 with mesothelioma, from necropsied Quebec chrysotile miners and millers from Asbestos township. Fibre concentrations in the lungs of these patients were compared with those in tissue from necropsies carried out on a local reference population: men who had died of either accidental death or acute myocardial infarction between 1990 and 1992. 23 were born before 1940 and 26 after 1940.

RESULTS: Geometric mean (GM) concentrations were higher in cases than in the controls for chrysotile fibers 5 to 10 microns long in patients with asbestosis with or without lung cancer; for tremolite fibers 5 to 10 microns long in all patients; for crocidolite, talc, or anthophyllite fibers 5 to 10 microns long in patients with mesothelioma; for chrysotile and tremolite fibers > or = 10 microns long in patients with asbestosis; and crocidolite, talc, or anthophyllite fibers > or = 10 microns long in patients with mesothelioma.

However, median concentrations of each type of fiber in the lungs did not show any significant differences between the three disease groups. Average length to diameter ratios of the fibers were calculated to be larger in patients with asbestosis and lung cancer than in those without lung cancer for crocidolite fibers > or = 10 microns long, for chrysotile, amosite, and tremolite fibers 5 to 10 microns long, and for chrysotile and crocidolite fibers < 5 microns long.

CONCLUSION: Lung cancers occurred in workers with asbestosis from Asbestos township that had an equal concentration of retained fibers but a tendency to a higher length to diameter ratio of amphiboles. These workers had a 29% higher average cumulative smoking index.