Chronic obstructive pulmonary disease in Welsh slate miners.
BACKGROUND
Exposure to respirable crystalline silica (RCS) causes emphysema, airflow limitation and chronic obstructive pulmonary disease (COPD). Slate miners are exposed to slate dust containing RCS but their COPD risk has not previously been studied.


OBJECTIVE
To study the cumulative effect of mining on lung function and risk of COPD in a cohort of Welsh slate miners and whether these were independent of smoking and pneumoconiosis.


METHODS
The study was based on a secondary analysis of Medical Research Council (MRC) survey data. COPD was defined as forced expiratory volume in 1 s/forced vital capacity (FEV1/FVC) ratio <0.7. We created multivariable models to assess the association between mining and lung function after adjusting for age and smoking status. We used linear regression models for FEV1and FVC and logistic regression for COPD.


RESULTS
In the original MRC study, 1255 men participated (726 slate miners, 529 unexposed non-miners). COPD was significantly more common in miners (n = 213, 33%) than non-miners (n = 120, 26%), P < 0.05. There was no statistically significant difference in risk of COPD between miners and non-miners when analysis was limited to non-smokers or those without radiographic evidence of pneumoconiosis. After adjustment for smoking, slate mining was associated with a reduction in %predicted FEV1[β coefficient = -3.97, 95% confidence interval (CI) -6.65, -1.29] and FVC (β coefficient = -2.32, 95% CI -4.31, -0.33) and increased risk of COPD (odds ratio: 1.38, 95% CI 1.06, 1.81).


CONCLUSIONS
Slate mining may reduce lung function and increase the incidence of COPD independently of smoking and pneumoconiosis.
National Heart and Lung Institute, Imperial College London, London SW3 6LR, UK, carl.reynolds@imperial.ac.uk.
C J
CJ
Reynolds
School of Social and Community Medicine, University of Bristol, Bristol BS8 2PS, UK.
S J
SJ
MacNeill
School of Health and Related Research, University of Sheffield, Sheffield S1 4DA, UK.
J
J
Williams
School of Health and Related Research, University of Sheffield, Sheffield S1 4DA, UK.
N G
NG
Hodges
School of Health and Related Research, University of Sheffield, Sheffield S1 4DA, UK.
M J
MJ
Campbell
National Heart and Lung Institute, Imperial College London, London SW3 6LR, UK.
A J
AJ
Newman Taylor
National Heart and Lung Institute, Imperial College London, London SW3 6LR, UK.
P
P
Cullinan
D000328:Adult; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D008906:Mining / Q000706:statistics & numerical data; D016273:Occupational Exposure / Q000009:adverse effects* / Q000706:statistics & numerical data; D011009:Pneumoconiosis / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology*; D013902:Radiography, Thoracic / Q000706:statistics & numerical data; D012822:Silicon Dioxide / Q000009:adverse effects*; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology; D011795:Surveys and Questionnaires; D013909:Thorax / Q000002:abnormalities; D014797:Vital Capacity; D014852:Wales / Q000453:epidemiology; D000078329:Workforce
D012822:Silicon Dioxide
Mineral dust; miners; occupational lung diseases.