Debilitating lung disease among surface coal miners with no underground mining tenure

Abstract

Objective: To characterize exposure histories and respiratory disease among surface coal miners identified with progressive massive fibrosis from a 2010 to 2011 pneumoconiosis survey.

Methods: Job history, tenure, and radiograph interpretations were verified. Previous radiographs were reviewed when available. Telephone follow-up sought additional work and medical history information.

Results: Among eight miners who worked as drill operators or blasters for most of their tenure (median, 35.5 years), two reported poor dust control practices, working in visible dust clouds as recently as 2012. Chest radiographs progressed to progressive massive fibrosis in as few as 11 years. One miner's lung biopsy demonstrated fibrosis and interstitial accumulation of macrophages containing abundant silica, aluminum silicate, and titanium dust particles.

Conclusions: Overexposure to respirable silica resulted in progressive massive fibrosis among current surface coal miners with no underground mining tenure. Inadequate dust control during drilling/blasting is likely an important etiologic factor.

FIGURE 1

(A) A small biopsy taken near the PMF lesion is visualized under light microscopy (H&E stain). The black box indicates the region viewed at higher power in images B and C. (B) Image viewed using bright-field light microscopy. (C) The same image viewed using polarized light imaging, where silica (weakly birefringent) and silicates (strongly birefringent) refract the polarized light and show up brighter than the surrounding lung tissue and other materials. Also, it shows fibrosis (collagen is very weakly birefringent). This same tissue is shown in Figure 2. H&E, hematoxylin and eosin; PMF, progressive massive fibrosis.

FIGURE 2

An example of a particle analyzed using SEM/EDS. (A) A small biopsy taken near the PMF lesion is visualized using SEM. This is the same portion of tissue visualized in Figure 1. The box indicates the region viewed at higher power in image B, showing hundreds of individual particles in macrophages. (B) Particle circled in yellow with a yellow cross-hair was individually analyzed to yield the EDS spectrum shown in image C. (C) The EDS spectrum peak indicating the analyzed particle is silica (showing only an elemental peak for silicon). EDS, energy dispersive x-ray spectroscopy; PMF, progressive massive fibrosis; SEM, scanning electron microscopy.

FIGURE 3

Miner 8’s chest radiographs. (A) A digitized copy of the radiograph that was taken at the age of 46 years and had no evidence of pneumoconiosis (small opacity profusion category 0/0 and no evidence of PMF). (B) Digital radiograph taken in NIOSH’s mobile surveillance unit 11 years later, at the age of 57 years, and was classified as small opacity profusion category 2/1 and PMF category A. Yellow arrows point to locations of PMF lesions. (C) Magnification of the indicated PMF lesion in the left lung. PMF, progressive massive fibrosis.

FIGURE 4

Photographs taken at the worksite by Miner 8. (A) Taken in 1981 at a surface coal mine, it shows a dust cloud enveloping the operator’s cab on a surface drill. (B) Taken in 2010 at a surface coal mine, it shows a cloud of dust around an Ingersoll Rand 45 drill and a worker to the left of the haul truck. (C) Taken in 2012 at a surface coal mine, it shows three miners enveloped in a dust cloud loading drill holes to blast overburden.