Debilitating Lung Disease Among Surface Coal Miners With No Underground Mining Tenure

Inhalation of respirable coal mine dust causes coal workers’ pneumoconiosis—a chronic, irreversible occupational lung disease. Progressive massive fibrosis (PMF) is a debilitating, advanced form of pneumoconiosis. The Federal Coal Mine Health and Safety Act of 1969 (Coal Act) established the federal permissible exposure limit (PEL) of 2.0 mg/m3 for respirable coal mine dust in underground and surface coal mines and mandated regular inspections of surface and underground mines, in an effort to prevent coal workers’ pneumoconiosis. Under the Coal Act, the Mine Safety and Health Administration (MSHA) required a reduced dust limit if the silica content in a dust sample exceeds 5%, effectively establishing a respirable silica PEL of 100 μg/m3. MSHA conducts periodic inspections at coal mines to assess compliance with these PELs. In 2014, MSHA issued a new rule1 reducing the PEL for coal mine dust to 1.5 mg/m3. The Coal Act also established a health surveillance system, administered by the National Institute for Occupational Safety and Health (NIOSH), designed to detect pneumoconiosis among working underground coal miners by offering periodic chest radiographs. Miners are not charged for participation in this voluntary program. Under Part 90 of the Coal Act, miners with evidence of pneumoconiosis are offered the opportunity to transfer to a less dusty occupation at the mine (if one exists). In 2012, there were more than 50,000 surface coal miners in the United States—44.3% of the coal mining workforce. Nevertheless, the benefits of pneumoconiosis surveillance under the Coal Act were not extended to surface miners until 2014. Consequently, surface miners did not generally have access to free periodic chest radiographs, and much less is known about the prevalence of dust-related lung disease in this group. Surface coal mining has generally been considered less dusty than underground mining; however, highwall drills at surface mining operations can generate large quantities of respirable dust containing significant levels of crystalline silica. Working as a surface driller is a recognized risk factor for pneumoconiosis.2–6 Drill operators and workers in the vicinity of the drill may experience exposure to hazardous dust levels. Table 1 summarizes results from dust sampling conducted by MSHA inspectors for drill operators and the blasting crew at surface coal mines.7 Many of the samples exceeded the MSHA PEL, and most were above the NIOSH-recommended exposure limit (50 μg/m3). TABLE 1 Percentage of MSHA Inspector Samples Collected From 1995 to 2012 With Excessive Silica7 Infrequent surveys conducted during the past 40 years have documented pneumoconiosis among US surface miners, generally at lower prevalence and less severity when compared with underground miners during the same periods.3–5,8 In 2010 to 2011, the mobile examination unit from the NIOSH Enhanced Coal Workers’ Health Surveillance Program (ECWHSP) traveled to 16 states with active surface coal mines and offered surface miners a free chest radiograph.9 Pneumoconiosis was found among 2.0% of the 2328 screened miners with at least 1 year of mining tenure. Twelve miners had radiographic changes consistent with PMF. Nine of these 12 miners reported no underground mining tenure.9 The objective of this study was to further characterize the work and medical histories of these miners who worked exclusively at surface mines and developed advanced pneumoconiosis.