| Subjects | Age (mean ± SD) | Sex | Current smokers | Employment years (mean ± SD) | Silica concentration |
| Exposed workers (n = 32) | 30.79 ± 8.59 | Male (n = 30; 93.75%); Female (n = 2; 6.25%) | N = 5 16.67% | 6.06 ± 2 | 5 ± 3.5 µmol/dl |