The incidence of pneumoconiosis, mesothelioma and other respiratory cancer in men engaged in mining and milling crocidolite in Western Australia

Abstract

Previous employees of a mining company, engaged in mining of crocidolite at Wittenoom Gorge in Western Australia between 1943 and 1966, have been traced to determine their incidence of asbestos-related diseases. Of 6200 male employees, 220 (3.5%) have developed pneumoconiosis and 26 have developed pleural mesothelioma. No cases of peritoneal mesothelioma have been identified. Prior to 1978, 60 men had died from respiratory cancer other than mesothelioma, compared with 38.25 expected from the mortality experience of all Western Australian males. The incidence of pneumoconiosis and mesothelioma and the mortality from other respiratory cancer all increased with duration of employment, interval from first employment, and level of occupational exposure, indicating a strong relationship between intensity of asbestos exposure and these diseases. The mortality ratio for respiratory cancer, excluding mesothelioma (1.57), was nearly twice that for all nonrespiratory causes of death, suggesting a two-fold increase in mortality from respiratory cancer compared with all Western Australian males. Variation of mortality from respiratory cancer by duration of employment and occupational exposure suggests that at least 30% of respiratory cancer deaths other than mesothelioma may be due to asbestos exposure. The major part of this excess is accounted for by respiratory cancer occurring in men with previously diagnosed pneumoconiosis.