Silicosis compensation in Western Australian gold miners since the introduction of an occupational exposure standard for crystalline silica.

Abstract

Occupational exposure limits for crystalline silica are under review worldwide because of the large numbers of exposed people and, especially, because of the recent International Agency for Research on Cancer classification of silica as a human carcinogen. The aims of this study were to (i) re-examine the incidence of silicosis in Western Australian gold miners and, using estimates of the total population at risk, (ii) estimate the upper confidence limit for the risk of silicosis in Western Australian gold miners since 1974, when the current exposure standard for crystalline silica was implemented. Work histories of cases compensated for pneumoconiosis after 1974 were examined. Numbers of workers in the total workforce likely to be exposed to crystalline silica in Western Australia were estimated as the population at risk. There were no cases of compensated silicosis in Western Australian miners whose first dust exposure began during or after 1974. The upper 95% confidence interval for this zero rate was estimated to be 4.8 per 100,000 person-yr. There have been no compensated cases of silicosis in Western Australia among miners first exposed to crystalline silica after introduction of the current exposure standard. A rate of compensated silicosis higher than five cases per 100,000 person-yr is unlikely.