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1969年美国煤矿卫生安全条例(FCMHSA)规定,从1970年起煤矿井下粉尘浓度应大幅度下降至3mg/m~3,1972年在粉尘中二氧化硅不超高者降为2mg/m~3。为了调查这种粉尘浓度是否导致煤工职业性肺疾患的下降,国立职业安全卫生研究所(NIOSH)进行了定期的流行病学调查。在最近的研究中,1970～1975年间NIOSH对美国一组井下矿工和离休矿工(3182名)进行了检查,研究了煤工尘肺(CWP)的患病率和发病率。1985～1988年间胸片由3名B组阅片者用1980 ILO尘肺分类法进行阅片,根据3名阅片者的中间值,CWP总患病率(本研究限于X线阴影密集度为1/0或以上)为6.8％。井下工作15～19年与20～24年的矿工比较,CWP的患病率有明显差异
1969 US Coal Mine Health and Safety Ordinance (FCMHSA) provides that since 1970, the coal mine dust concentration should be drastically reduced to 3mg / m ~ 3, in 1972 the dust is not too high silica reduced to 2mg / m ~ 3 . To investigate whether this concentration of dust causes a drop in occupational lung conditions in coal miners, the National Institute for Occupational Safety and Health (NIOSH) conducted a regular epidemiological survey. In a recent study, NIOSH conducted a survey of a group of 3182 miners and retired miners in the United States from 1970 to 1975 to study the prevalence and incidence of CWP. From 1985 to 1988, chest radiographs were read by 3 group B readers using the 1980 ILO pneumoconiosis classification. The median prevalence of CWP was based on the median of 3 readers (this study was limited to 1 with a shaded x-ray intensity of 1 / 0 or above) is 6.8%. Downhole work 15 to 19 years compared with 20 to 24 years of miners, CWP prevalence was significantly different