Proceedings, Eighth International Conference on Occupational Lung Diseases, Prague, Czechoslovakia, September 14-17, 1992 1993;:568-573
The results of an analysis of temporal trends in the incidence of coal workers pneumoconiosis (CWP) among underground United States coal miners were discussed. Data were taken from the Coalworker X- ray Surveillance Program (CWXSP), which has been administered by NIOSH since 1970. Under the provisions of the program, miners were offered a free chest X-ray every 5 years. The films were read for opacities by a team of NIOSH certified B-readers using International Labour Office (ILO) criteria. If an X-ray contained evidence of CWP, the miner had the right to transfer to work in a less dusty environment. The CWXSP was divided administratively into four time periods, denoted rounds, which started in 1970, 1973, 1978, and 1981. More than 250,000 chest X-ray films have been collected under CWXSP since the 1970s. Analysis of these shows that the prevalence of ILO category 1+ and category 2+ rounded opacities and large opacities when stratified by years of underground mining (tenure) decreased over time. The prevalence rates for category 1+ opacities observed in rounds 1, 2, 3, and 4 adjusted to a common tenure distribution were 8.0, 7.3, 4.6, and 2.0%, respectively. The corresponding tenure adjusted prevalence rates for category 2+ opacities were 2.0, 1.0, 0.5, and 0.3. The rates of participation of miners with 1 or more years of tenure in rounds 1, 2, 3, and 4 were 50, 44, 32, and 30%, respectively. The authors conclude that despite limitations, the CWXSP data indicate that the prevalence of CWP has decreased over time. This finding is consistent with the results of concurrent epidemiological investigations and coincides with decreases in dust exposures in coal mines that were mandated after 1969.
Proceedings, Eighth International Conference on Occupational Lung Diseases, Prague, Czechoslovakia, September 14-17, 1992