[Dose-response relationship between different respirable coal dust exposures and pneumoconiosis risk]

Objective: To investigate the dose-response relationship between the cumulative dust exposures to anthracite, bituminous coal, and lignite and the cumulative prevalence rates of pneumoconiosis due to the exposures, respectively and provide a basis for scientific development of occupational health standards. Methods: Investigation on the exposure to coal dust and pneumoconiosis prevalence was conducted in 9 state-owned coal mines. The cumulative anthracite, bituminous coal, and lignite dust exposure specific cumulative prevalence rates of pneumoconiosis were calculated by life table method, respectively. The linear regression equations were used to control the unilateral interval to obtain the exposure concentration limits of the respirable coal dust, respectively. Results: A total of 21 000 coal miners in the 9 coal mines were included in the study. The detection rates of pneumoconiosis in coal miners in anthracite, bituminous coal and lignite mines were 11.27%, 21.32%, and 6.00%. The average lengths of exposure to coal dust at pneumoconiosis onset were 20.12 years, 22.88 years, and 25.21 years, respectively and the dose-response relationships between the cumulative respirable coal dust exposure and the cumulative prevalence rates were all linear regression equations, which are y=5.788x-16.043 (R(2)=0.949), y=5.679x-16.837 (R(2)=0.904), and y=6.465x-19.573 (R(2)=0.944), respectively. Supposing that the safety coefficient is 1.2, when the cumulative prevalence rate of pneumoconiosis after 30 years of exposure to dust is not higher than 1%, the exposure concentration limits of the three types of respirable coal dust are 1.7, 2.3, and 3.9 mg/m(3), respectively. Conclusions: The results of this study shows that the detection rate of pneumoconiosis, the average length of exposure to coal dust at pneumoconiosis onset, and the exposure concentration limits of the respirable coal dust varied with coal types. In the case of the same cumulative level of coal dust exposure, the lower the coal volatiles is (i.e. the higher the carbon content is), the higher the cumulative prevalence rate of pneumoconiosis is (anthracite>bituminous coal>lignite). It is suggested to develop national occupational health standards of coal dust exposure according to the grades of coal.