ASBESTOS AND NONASBESTOS FIBER CONTENT IN LUNG-TISSUE OF JAPANESE PATIENTS WITH MALIGNANT MESOTHELIOMA

Background. Pulmonary fiber content of both asbestos and nonasbestos t ypes were evaluated in Japanese patients with malignant pleural mesoth eliomas. Methods. Pulmonary fiber content was analyzed in 16 patients and 16 case-matched control subjects by transmission electron microsco py with energy-dispersive X-ray analysis using a low-temperature ashin g procedure. Results. The geometric mean content of total asbestos was significantly higher in the patients (22.0 X 10(6) fibers/g dry lung) than in the control subjects (2.24 X 10(6) fibers/g dry lung) (P < 0. 01). When the asbestos content was analyzed by fiber type, the geometr ic means were also consistently and significantly higher among the pat ients compared with the control subjects (P < 0.01). Results were as f ollows: (1) amosite: patients 3.94 times 10(6) versus control subjects 0.23 X 10(6); (2) crocidolite: patients 3.56 times 10(6) versus contr ol subjects 0.35 times 10(6); (3) total amphiboles: patients 16.0 time s 10(6) versus control subjects 0.77 times 10(6); and (4) chrysotile: patients 3.76 times 10(6) versus control subjects 1.01 times 10(6). Ho wever, when individual total asbestos content was considered, 7 of the 16 patients (44%) had levels lower than the highest value noted among the control subjects. Pulmonary fiber content of patients and control subjects also revealed the presence of nonasbestos fibers. The geomet ric mean of nonasbestos fibers was significantly higher in the patient s (87.3 x 10(6)) than in control subjects (33.8 X 10(6)) (P < 0.01). T he major type of nonasbestos fibers in both groups was aluminum silica tes. The mean of ratios of nonasbestos fiber contents to total asbesto s contents in the patients and control subjects was 7.0 and 17.3, resp ectively. Conclusions. The results were mainly in agreement with the f indings of earlier investigations, but fiber content of both chrysotil e and nonasbestos fiber as well as those of amphibole asbestos were si gnificantly higher in the patients than in the control subjects.