SOURCE: NIOSH | April 16, 2026
On this Workers Memorial Day, please join me in remembering and honoring workers who have died or suffered injury or illness in the workplace. At NIOSH, we recognize that the burden of workplace death, injury, and illness is tremendous. When a worker dies, their family, friends, and community carry this lifelong burden.
In keeping with the NIOSH vision of Safer, Healthier Workers, our research focuses on preventing work-related death, injury, and illness. Whether in the laboratory or in the field, our research is guided by the health and safety needs of the U.S. workforce.
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Prevalence of Reduced Mid-Expiratory Flow Among Coal Workers’ Health Surveillance Program Participants
By Laura Kurth, Noemi B. Hall, Brian Ansell, A. Scott Laney, and David J. Blackley, NIOSH
Why is this study important?
Coal miners who breathe in coal mine dust are at risk of lung disease. Symptoms may be mild to severe, depending on exposure amount and length. An early sign of obstructive lung disease is reduced airflow during the middle part of exhaling, caused by limited airflow through the small airways of the lung.
Early detection of lung damage from breathing in coal mine dust is important to prevent more serious disease. To this end, the NIOSH Coal Workers’ Health Surveillance Program provides lung function testing and chest X-rays to coal miners throughout the United States.
How did you do the study?
We calculated the number of coal miners with possible small airways disease based on their lung function testing results. We analyzed lung function, chest X-ray, and survey results from more than 7,000 coal miners who did not have obstructive lung disease based on standard lung function tests (spirometry). The miners participated in the program from August 2014 through December 2022. We defined signs of small airways disease as mid-expiratory airflow less than 65% of the predicted value when exhaling forcefully.
What did you find?
About 7% of coal miners without obstructive lung disease by spirometry had evidence of small airways disease. Older age, longer tenure, and X-ray evidence of black lung disease were associated with a greater likelihood of small airways disease. Almost 11% of miners aged 60 and older had signs of small airways disease, compared with nearly 4% of miners under 40. About 17% of those with signs of black lung disease on X-ray also had signs of small airways disease.
What are the next steps?
To prevent small airways disease, it is important to reduce coal miners’ exposure to coal mine dust. This study shows that signs of small airways disease are common in coal miners even when other spirometry measures are normal. These signs may be an early indicator that the disease could progress.
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