Table 2 Comparison of basic characteristics, job exposure, and protective equipment usage between low and high respirable crystalline silica exposure groups
|  | Low exposure | High exposure | P value |
|---|---|---|---|
n = 28 | n = 37 | ||
Age, mean ± SD, yr | 44.0 ± 14.0 | 39.9 ± 9.2 | 0.153 |
Male, n (%) | 16 (57.1) | 35 (94.6) | 0.0003 |
Body mass index, mean ± SD | 24.6 ± 4.2 | 26.6 ± 4.9 | 0.126 |
Education attainment > = 13 yrs, n (%) | 23 (82.1) | 18 (48.7) | 0.006 |
Tobacco smoking, n (%) | Â | Â | 0.051 |
 Never | 19 (67.9) | 20 (54.1) |  |
 Ex-smoker | 0 (0) | 7 (18.9) |  |
 Current smoker | 9 (32.1) | 10 (27.0) |  |
Cumulative smoking amount, mean ± SD, pack*yr | 9.1 ± 10.3 | 7.4 ± 8.5 | 0.699 |
Tenure, year, mean ± SD | 6.0 ± 6.8 | 6.0 ± 4.3 | 0.989 |
Weighting factor, mean ± SD | 1.3 ± 0.9 | 5.1 ± 3.2 | < 0.0001 |
Weighting factor > median (2), n (%) | 4 (12.1) | 29 (87.9) | < 0.0001 |
Weighted tenure, mean ± SD, year | 6.9 ± 10.1 | 26.6 ± 20.9 | < 0.0001 |
Cumulative RCS exposure, mean ± SD, mg/m3-year | 0.15 ± 0.33 | 6.23 ± 9.06 | < 0.0001 |
Best respiratory PPE used at work |  |  | < 0.0001 |
 No or regular flat mask, n (%) | 3 (10.7) | 1 (2.7) |  |
 N95, n (%) | 18 (64.3) | 5 (13.5) |  |
 Half-face mask, n (%) | 2 (7.1) | 10 (27.0) |  |
 Full-face mask, n (%) | 2 (7.1) | 15 (40.5) |  |
 PAPR, n (%) | 3 (10.7) | 6 (16.2) |  |
Fit test experience, n (%) | 0 (0) | 8 (21.6) | 0.008 |