The voluntary Coal Workers' Health Surveillance Program stipulates that active coal miners be offered no-cost medical monitoring that includes a chest radiograph at entry into coal mining and then at approximately 5-year intervals. During August 2011–July 2016, a total of 99 unique cases of PMF were detected nationwide by the Coal Workers' Health Surveillance Program, including 19 in Kentucky residents. Although surveillance data have indicated a resurgence of PMF in recent years (Figure 1), this large cluster of cases brought to the attention of NIOSH by a single local radiologist was not discovered through the national surveillance program offered to active miners. The finding in the current report of 56 cases among Kentucky residents indicates that many cases were not identified through routine national surveillance; however, this finding is consistent with historically low Coal Workers' Health Surveillance Program participation rates among Kentucky coal miners: during 2011–16 only 17% of Kentucky coal miners participated (personal communication, Coal Workers' Health Surveillance Program data, October 5, 2016).
The factor or combination of factors that led to this increase in cases of PMF in eastern Kentucky and whether there are more unrecognized cases in neighboring coal mining regions are unknown. Because PMF takes years to become manifest, the specific exposures or mining practices that led to these cases are also unknown. New or modified mining practices in the region might be causing hazardous dust exposures. While obtaining detailed occupational histories, the reporting physician identified the practice of "slope mining" as a potential exposure in eastern Kentucky (slope mining involves teams of miners operating continuous miner machines, designed to cut coal and other soft rock, to cut shafts through hundreds of feet of sandstone to reach underground coal seams) (Figure 2). The sandstone formation underlying eastern Kentucky is >90% quartz, and dust generated during the slope cutting could expose miners to hazardous dust containing high concentrations of respirable crystalline silica. Previous research found that 25 of 37 (68%) Kentucky and Virginia coal miners with "advanced pneumoconiosis" (defined as PMF or simple coal workers' pneumoconiosis with high small opacity profusion) reported working as roof bolters, a mining job associated with high silica dust exposure. The current investigation was limited to miners with PMF and found that 26 (43%) reported working as roof bolters, and 20 (33%) reported working as continuous miner operators. Operating a continuous miner machine has typically been considered a "coal-face position" (i.e., a work position located at the face, or seam, of coal), and therefore not a position usually associated with higher silica dust exposures. However, the use of a continuous miner machine during shaft cutting or thin seam coal mining (i.e., occurring when the height of the coal seam requires that rock above and below the coal seam is cut along with the coal) requires cutting through rock and creates the potential for respirable silica exposures, which might explain why working as a continuous miner operator could pose an increased risk for PMF.
In addition, recent industry trends might have led to a higher number of miners seeking radiographs, either to gather information about their health status or to seek benefits through state workers' compensation or federal black lung programs. A steep decline in coal miner employment and coal production during recent years has occurred, with 1,501 jobs lost in Kentucky (17.9% of state coal workforce) during the first quarter of 2016. Miners might feel that future coal-related employment is unlikely and that previous barriers to health-seeking behaviors have been removed. For example, in Kentucky a miner has 3 years to file a state compensation claim "after the last injurious exposure to the occupational hazard or after the employee first experiences a distinct manifestation of an occupational disease in the form of symptoms reasonably sufficient to apprise the employee that he or she has contracted the disease, whichever shall last occur."¶ Because the earlier stages of coal workers' pneumoconiosis can be associated with few or no overt symptoms, and because coal mining jobs have historically been among the best-paying in the region, some miners might have chosen to not seek radiographs or other health-related information during the earlier stages of their career to avoid threatening their ability to continue working in the industry.
The findings in this report are subject to at least three limitations. First, the cases highlighted in this report represent the recent experience of one single-radiologist practice in eastern Kentucky and might underestimate the actual extent of PMF in coal miners in the broader region. Second, classifications of chest radiographs were performed by a single B Reader, who was aware of miners' occupational histories and other clinical data, such as results of chest computed tomography scans. For classifications performed for worker monitoring and surveillance, NIOSH recommends that a single reader is generally sufficient, particularly for radiographs that are clearly normal or abnormal. However, for radiographs with findings at the boundary between normal and abnormal, or for settings such as epidemiologic research or contested proceedings where it is important to ensure a high degree of accuracy, NIOSH recommends summary classifications derived from multiple independent readers and is taking measures to obtain independent confirmation of the classifications by sending them to additional B-readers. Finally, cases in this report were not identified through standard coal workers' pneumoconiosis surveillance, and whether similar clusters of cases exist in other communities is not known. Thus, the actual extent of PMF in U.S. coal miners remains unclear. Because the cases described in this report were identified during a span of fewer than 2 years and previous radiographs were not available, it was not possible to ascertain the time of PMF onset for these patients.
Although PMF is preventable through well-established dust control practices, each of the 60 patients in this report was exposed to coal mine dust over a period of years in an amount sufficient to cause this severe disease. Finding these cases in such a small geographic area is a strong signal that action is needed in the area to identify existing cases at an earlier stage and prevent future cases. A new federal rule has been implemented to protect all U.S. coal miners through expansion of medical surveillance, including respiratory symptom assessment and spirometry testing. The rule also mandates lowering the amount of respirable dust allowed in U.S. coal mines and the use of a continuous personal dust monitor, a device that can measure respirable coal mine dust in real time. Availability of real-time respirable dust measurements, lower exposure limits, and expanded medical surveillance are intended to prevent future cases and identify early signs of respiratory impairment in coal miners before a disabling condition has developed.
The findings in this report serve as a reminder that more than 45 years after the Coal Act's passage, one of its core objectives has not been achieved. In the coming years, NIOSH will focus active surveillance measures on miners in central Appalachia and will continue to work with miners, mine operators, regulatory and disability compensation agencies, and others to better characterize the scope of the problem, expand educational outreach to miners to increase their awareness of the right to confidential medical screening, and prevent overexposures to coal mine dust.
Heather Wilson, United Medical Group; the NIOSH Coal Workers' Health Surveillance Program; participating miners.
Morbidity and Mortality Weekly Report. 2016;65(49):1385-1389. © 2016 Centers for Disease Control and Prevention (CDC)