Chrysotile Mine Research Articles

Radiographic changes in chrysotile asbestos mine and mill workers of Quebec.

Radiographic changes in 13,021 employees were assessed in 6,529 men aged 36 to 65. The prevalence of rounded small opacities (category 1/0 or more) rose with increasing dust exposure from 0.5% to 3.4%; that of irregular small opacities (category 1/0 or more), from 2.2% to 17.0%; and that of pleural thickening (grade 1 or more), from 1.4% to 12.3%. Small opacities or pleural changes were seen in 17% of men, but 3.2% had both. At present dust exposure levels, much lower rates can be expected. The prevalence of radiologic changes was higher in the Thetford Mines area than in the Asbestos area. This was shown by pleural changes more than parenchymal changes, and the difference was extreme with pleural calcification which was common in Thetford Mines but virtually absent in Asbestos.

Dust Exposure in the Chrysotile Asbestos Mines and Mills of Quebec

Past and present features of the Quebec chrysotile mining and milling environment and methods used to establish indices of exposure for epidemiological studies are described. Environmental dust concentrations used for calcuation of dust exposure indices were derived mainly from systematic midget-impinger samples taken since 1948, and from field surveys made in 1968, using impinger and a variety of other techniques. Though dust levels within the industry fluctuated widely, there was a steady fall from an average of approximately 75 million particles per cubic foot (MPCF) in 1948 to less than 10 MPCF in 1968. Considerable variation in the fiber content of airborne dust in this industry suggests that any safety standard should probably take account of fibrous and nonfibrous components.