Relationship between occupations and asbestos-fibre content of the lungs in patients with pleural mesothelioma, lung cancer, and other diseases.

, 377-386. The light-visible asbestos-fibre content of 300 lung specimens has been measured using a potash-digestion and phase-contrast microscopy technique, and the results have been correlated with the occupations of the patients. Among 100 pleural mesothelioma specimens were 88 where the patients had been exposed to asbestos, and in 73 of these (83%) the lung tissue contained over 100 000 asbestos fibres per gram of dried lung, and only one specimen showed less than 20 000 fibres per gram. When asbestosis was present, the lungs nearly always showed over 3 million fibres per gram. In 100 control lungs (those without industrial disease or lung cancer) there were less than 20 000 fibres per gram of dried lung in 71% of specimens. Lungs from 100 patients with lung cancer but no industrial disease contained less than 20 000 fibres per gram of dried lung in 80% of cases. Patients with parietal pleural plaques nearly all had over 20 000 fibres per gram in their lungs. The number of asbestos fibres found in the lungs was closely related to the occupations of the patients but not to their home environment. Patients who had lived near likely sources of atmospheric asbestos pollution did not have higher asbestos fibre counts than the rest of the patients. It is concluded that there is a definite dose relationship between asbestos exposure and mesothelioma formation but that' `sub-asbestosis' levels of asbestos exposure do not contribute to the formation of lung cancer in those not subjected to industrial asbestos exposure.