Table 4.
Silicosis (defined as ILO ≥1/1) hazard ratios (HRs) and 95% confidence intervals (95% CI) for the full cohort, lagged 10 years and limited to those hired since 1960, by categories of cumulative exposure (mg/m3-years), average exposure (mg/m3), and duration of employment (decades), all controlling for smoking; and smoking status.
| HR (95% CI) | ||||||
|---|---|---|---|---|---|---|
| Full Cohort | Exposure lagged 10 yrs | Limited to those hired since 1960 | ||||
| Observed | Observed | Observed | ||||
| Cumulative exposure | ||||||
| ≤0.5 | 4 | Reference | 5 | Reference | 4 | Reference |
| >0.5–1.0 | 2 | 0.9 (0.1–5.5) | 3 | 1.8 (0.4–8.8) | 2 | 0.9 (0.1–5.3) |
| >1.0–1.5 | 2 | 1.3 (0.2–8.1) | 1 | 0.9 (0.1–8.3) | 2 | 1.3 (0.2–8.4) |
| >1.5–3.0 | 2 | 0.8 (0.1–5.1) | 2 | 1.0 (0.2–6.0) | 1 | 0.8 (0.1–8.3) |
| >3.0–4.0 | 3 | 3.3 (0.6–18.1) | 5 | 7.0 (1.6–30.7) | 3 | 6.1 (1.1–32.8) |
| >4–5 | 4 | 6.5 (1.3–32.4) | 4 | 7.2 (1.5–33.8) | 2 | 10.2 (1.6–66.3) |
| >5–6 | 7 | 10.5 (2.4–46.2) | 5 | 9.6 (2.2–42.5) | 1 | 9.1 (0.9–94.5) |
| >6 | 24 | 9.2 (2.3–36.8) | 23 | 11.3 (3.1–41.8) | 5 | 14.5 (3.0–69.6) |
| Average exposure‡ | ||||||
| ≤0.05 | 6 | Reference | ||||
| >0.05–0.1 | 2 | 0.9 (0.2–4.7) | ||||
| >0.1–0.15 | 4 | 4.0 (1.1–15.2) | ||||
| >0.15–0.2 | 10 | 11.1 (3.6–34.4) | ||||
| >0.2 | 26 | 20.0 (7.5–53.1) | ||||
| Years employed | ||||||
| ≤10 | 3 | Reference | 3 | Reference | ||
| >10–20 | 6 | 0.8 (0.2–3.5) | 6 | 0.8 (0.2–3.5) | ||
| >20–30 | 15 | 1.7 (0.4–7.0) | 10 | 1.2 (0.3–5.1) | ||
| >30 | 24 | 1.2 (0.3–4.7) | 1 | 0.2 (<0.1–2.6) | ||
| Smoking | ||||||
| Never | 12 | Reference | 3 | Reference | ||
| Ever | 24 | 2.4 (1.2–4.9) | 4 | 4.4 (1.3–15.6) | ||
| Unknown | 12 | 0.6 (0.3–1.4) | 13 | 1.6 (0.4–7.1) | ||
Age was used as the time variable. ‡Additionally adjusted for duration of employment.