Pneumoconiosis among underground bituminous coal miners in the United States: is silicosis becoming more frequent?
OBJECTIVE
Epidemiological reports since 2000 have documented increased prevalence and rapid progression of pneumoconiosis among underground coal miners in the United States. To investigate a possible role of silica exposure in the increase, we examined chest x-rays (CXRs) for specific abnormalities (r-type small opacities) known to be associated with silicosis lung pathology.


METHODS
Underground coal miners are offered CXRs every 5 years. Abnormalities consistent with pneumoconiosis are recorded by National Institute for Occupational Safety and Health (NIOSH) B Readers using the International Labour Organization Classification of Radiographs of Pneumoconioses. CXRs from 1980 to 2008 of 90 973 participating miners were studied, focussing on reporting of r-type opacities (small rounded opacities 3-10 mm in diameter). Log binomial regression was used to calculate prevalence ratios adjusted for miner age and profusion category.


RESULTS
Among miners from Kentucky, Virginia and West Virginia, the proportion of radiographs showing r-type opacities increased during the 1990s (prevalence ratio (PR) 2.5; 95% CI 1.7 to 3.7) and after 1999 (PR 4.1; 95% CI 3.0 to 5.6), compared to the 1980s (adjusted for profusion category and miner age). The prevalence of progressive massive fibrosis in 2000-2008 was also elevated compared to the 1980s (PR 4.4; 95% CI 3.1 to 6.3) and 1990s (PR 3.8; 95% CI 2.1 to 6.8) in miners from Kentucky, Virginia and West Virginia.


CONCLUSIONS
The increasing prevalence of pneumoconiosis over the past decade and the change in the epidemiology and disease profile documented in this and other recent studies imply that US coal miners are being exposed to excessive amounts of respirable crystalline silica.
Division of Respiratory Disease Studies, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, 1095 Willowdale Road, Mail Stop HG900.2, Morgantown, W V 26505-2888, USA. alaney@cdc.gov
A Scott
AS
Laney
Edward L
EL
Petsonk
Michael D
MD
Attfield
D000328:Adult; D055008:Anthracosis / Q000000981:diagnostic imaging / Q000453:epidemiology; D003032:Coal Mining; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis; D015995:Prevalence; D011658:Pulmonary Fibrosis / Q000000981:diagnostic imaging / Q000453:epidemiology / Q000209:etiology; D011859:Radiography; D012829:Silicosis / Q000000981:diagnostic imaging / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology