Important Medical Study Details Severe Black Lung Among Surface Miners

Miner 6 reported 9 years of work as a contract blaster at surface coal mines, and 1 year as a haul truck operator, driller, and maintenance worker for a coal company before his survey chest radiograph showing PMF. As a contract blaster, he reported many days on which he worked for several hours in dust clouds generated by drilling rigs. He asserted that the contract employer did not provide either a respiratory protection program or training about dust hazards, and he did not recall any personal dust sampling. In contrast, during the 1 year he worked as a mining company employee, Miner 6 described regular use of dust collectors and air-conditioned cabs, and he perceived lower dust exposure compared with his years of contract work. The mining company had also performed dust measurements to assess compliance with regulations. Miner 6 did report exposure to intermittent dust clouds during the use of compressed air on equipment maintenance and blowing dust out of filters.

Miner 8 described variable but often very dusty working conditions. Many of the drills he operated did not have effective dust collectors. Frequently, drills did not have cabs; a drill designed for wet drilling (not equipped with a cab or dry dust collector) was regularly operated without water. On drills with cabs, the air-conditioning system was often in poor operating condition, and dust would recirculate inside the cab. On early model drills, it was frequently necessary to open cab doors to avoid the dust and extreme heat emitted by the drill machinery. At times, to avoid extreme heat or dust, he left the cab while drilling. To document his assertions, he provided photographs illustrating the working conditions he experienced at surface mines throughout his career. These showed workers exposed to clouds of dust at the drill site (Fig. 4 representative examples). Miner 8 reported that personal dust sampling was done a few times per year when federal mine inspectors were on the job site, but he denied
existence of a respiratory protection program or of being informed of dust sampling results.

At the age of 56 years, Miner 8 began having shortness of breath and cough with moderate physical activity. Previously, he had been physically active and without symptoms, and had never smoked. After receiving a report of PMF on his survey radiograph, he sought medical care. His lung function was found to be significantly reduced and exhibited a restrictive pattern: forced expiratory volume in 1 second was 75%, forced vital capacity was 69%, and total lung capacity was 62% of the predicted reference values. Cardiopulmonary exercise testing revealed a low partial pressure of oxygen (pO2) at peak exercise and no evidence of any cardiac limitation. His physician diagnosed him with severe silicosis with PMF and advised him to leave mining.

Even though all of the miners in this study worked their entire careers under the provisions of the 1969 Coal Act, study results show that severe forms of pneumoconiosis continue to occur in miners whose occupational exposure occurred exclusively through surface coal mining work. Supplemental information provided by some participants indicated that dust controls were often insufficient at their worksites. Given that surface coal miners make up a substantial portion (44%) of the coal mining workforce, the case series results and ongoing silica overexposures documented by MSHA sampling highlight the need to reduce respirable dust exposures at surface mining operations and demonstrate the need for including surface miners in routine respiratory health surveillance.