Carcinogenic Asbestos Fibers in the Parietal Pleura

Abstract

The role of asbestos fibers in the development of lesions of the parietal pleura and especially mesothelioma is unclear. Based on the experimental findings of Stanton (1981) with intrapleural asbestos injections in animals, it is generally accepted that fibers more than 8μ in length and less than 0.25 μ in diameter are the most carcinogenic. More recently, the same toxicity was attributed to fibers 5μ or more long (Jaurand 1991). The presence of such fibers is controversial. In man (Boutin 1981, Sebastien 1980, Dodson 1990, Kohyama 1991) as well as in experimental animals (Rey 1993), most of the fibers observed have been short (<3μ). Studies have also demonstrated a lack of correlation between the concentration of asbestos fibers in lung tissue and the results of biopsy of parietal pleura samples. This discrepancy has been explained by the heterogeneous topographical distribution of fibers in the parietal pleura (Sebastien 1980). Thoracoscopic observation of “anthracotic spots” near lymphatic vessels suggest that exogenous particle may collect there. The purpose of this study was to detect the presence of potentially carnogenic asbestos fibers (i.e. 5μ or longer) in the parietal pleura of patients with a history of exposure to asbestos and to determine if fibers collect preferentially in anthracotic areas.