FIBER ANALYSIS IN LUNGS OF RESIDENTS OF A JAPANESE TOWN WITH ENDEMIC PLEURAL PLAQUES

The authors analyzed various types of fibers in lung-tissue samples, w hich were obtained from 50 cases (46 surgical resections and 4 autopsi es) at Kumamoto-Minami Hospital in Matsubase, where the occurrence of pleural plaques is endemic. Lung cancer necessitated surgical resectio n in 44 cases. Eleven of the 50 cases were residents of Matsubase; 15 resided in the region around the town, where the frequency of pleural plaques was slightly higher; and 24 cases lived in a region with norma l plaque frequency. The number of anthophyllite fibers in the lungs of town residents was significantly higher than in residents of the regi on with normal plaque frequency. In 6 cases, the authors found accompa nying pleural plaques, and the anthophyllite fiber count in the lungs in these cases was significantly higher than in cases without plaques. In addition, the anthophyllite fiber counts in 2 cases with severe pl aques were significantly higher in 4 cases with only mild plaques. The se results suggested that anthophyllite fiber might be responsible for the increased prevalence of pleural plaques in Matsubase. Even though the anthophyllite fibers were quite long (mean length = 25.1 mu m), t he width of most anthophyllite fibers were thick (mean diameter = 0.84 mu m). Therefore, the aspect ratio of anthophyllite (mean = 38.7) was lower than that of amosite (mean = 81.8), which, in a previous report , was found predominantly in cases of pleural mesothelioma. Perhaps th ese differences in fiber size are related to the strength of the carci nogenicity to the pleura.