Categories of silica exposure and smoking habits among silica exposed RA cases and silica exposed controls
| Category of silica exposure | Number of exposed cases/controls* | Number of smokers among exposed cases/controls* |
|---|---|---|
| *Cases and controls may belong to more than one category of silica exposure. | ||
| Rock drilling | 12/6 | 10/3 |
| Stone crushing | 9/5 | 9/4 |
| Stone dust (unspecified) | 33/18 | 30/14 |
| Silica exposure overall | 41/20 | 37/15 |