The CDC is reporting a cluster of patients with advanced black lung disease, or Progressive Massive Fibrosis (PMV) in eastern Kentucky. That fits in with a trend of increasing prevalence of the disease, according to the CDC’s monitoring efforts.

In the late 1990s the prevalence of PMF among miners participating in the Coal Act’s voluntary surveillance program was less than 1%. By 2014 it had spiked to around 5%.

“It is clear that we still have too many miners being exposed to too much dust,” [NIOSH epidemiologist David J.] Blackley said.

The newly reported PMF cluster involved miners residing in four contiguous counties in southeastern Kentucky (Floyd, Knott, Letcher, and Pike) that are part of the central Appalachia coalfield region.

The current and former miners had worked in coal mines for a mean of 29.2 years (range of 15 to 47 years), and their mean age at diagnosis was 60.3 (range of 44.9 to 77.4). All 60 patients had radiographic evidence of pneumoconiosis, and seven had large, rounded opacities on radiograph indicative of silicosis lung pathology.

“The factors 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,” the investigators wrote.