Spirometry and chest radiograph results among active underground Kentucky, Virginia, and West Virginia coal miners participating in Enhanced Coal Workers’ Health Surveillance Program (ECWHSP), by mine size, September 2005–December 2012, n=3771
| Small mine (n=908) | Large mine (n=2863) | Effect measure* | 95% CI | |
|---|---|---|---|---|
| Spirometry | ||||
| Abnormal, n (%) | 168 (18.5) | 383 (13.4) | 1.38 | 1.17 to 1.62 |
| Obstructive† | 61 (6.7) | 132 (4.6) | 1.46 | 1.09 to 1.96 |
| Restrictive | 84 (9.3) | 214 (7.5) | 1.24 | 0.97 to 1.58 |
| Mixed | 23 (2.5) | 37 (1.3) | 1.96 | 1.17 to 3.28 |
| % pred FEV1, mean (SD) | 92.60 (15.2) | 95.24 (14.1) | −2.64 | −1.52 to −3.76 |
| % pred FVC | 96.39 (13.0) | 97.68 (12.4) | −1.30 | −0.33 to −2.26 |
| FEV1/FVC | 75.53 (8.4) | 76.49 (7.5) | −0.97 | −0.35 to −1.58 |
| ILO classification | ||||
| CWP, n (%) | 98 (10.8) | 148 (5.2) | 2.09 | 1.64 to 2.67 |
| Category 1‡ | 69 (7.6) | 97 (3.4) | 2.24 | 1.66 to 3.03 |
| Category 2 | 25 (2.8) | 38 (1.3) | 2.07 | 1.26 to 3.42 |
| Category 3 | 4 (0.4) | 13 (0.5) | 0.97 | 0.32 to 2.97 |
| PMF, n (%) | 22 (2.4) | 31 (1.1) | 2.24 | 1.30 to 3.85 |
| Adjusted results | ||||
| Abnormal spirometry | 1.37 | 1.16 to 1.61 | ||
| CWP | 2.13 | 1.68 to 2.70 | ||
*Effect measures for ‘Spirometry’ and ‘ILO Classification’ categories are unadjusted. Prevalence ratios and 95% CIs are presented for frequency comparisons; differences in means and 95% CIs are presented for mean comparisons. Prevalence ratios for ‘Adjusted Results’ are adjusted as follows: ‘Abnormal Spirometry’ for underground mining tenure, body mass index, and smoking status; ‘CWP’ for underground mining tenure and smoking status. Large mines are the referent for each comparison.
†Spirometric patterns of abnormality are defined as follows: obstructive pattern: FEV1/FVC<LLN; and FVC>LLN; and FEV1<LLN; restrictive pattern: FEV1/FVC>LLN; and FVC<LLN; and mixed pattern: FEV1/FVC<LLN; and FVC<LLN.
‡International Labour Office subcategories for small opacities.
CWP, coal workers’ pneumoconiosis; FEV1, forced expiratory volume in 1 s; FVC, forced vital capacity; ILO, International Labour Office; LLN, lower limits of normal; % pred, per cent predicted PMF, progressive massive fibrosis.