Table 2.
Lung Cancer Odds Ratios Associated with Various Indices of Occupational Silica Exposure
| Occupational Silica Exposure | Cases (n) | % | Control Subjects (n) | % | OR* | 95% CI |
|---|---|---|---|---|---|---|
| Never | 11,978 | 70.9 | 16,477 | 78.6 | 1.0 | Referent |
| Ever exposure | 4,923 | 29.1 | 4,488 | 21.4 | 1.30 | 1.23–1.38 |
| Duration, yr | ||||||
| 1–9 | 2,035 | 12.0 | 1,936 | 9.2 | 1.22 | 1.12–1.31 |
| 10–19 | 926 | 5.5 | 905 | 4.3 | 1.20 | 1.08–1.34 |
| 20–29 | 635 | 3.8 | 519 | 2.5 | 1.45 | 1.26–1.66 |
| >29 | 1,327 | 7.9 | 1,128 | 5.5 | 1.48 | 1.34–1.63 |
| Test for trend, P value | <0.01 | |||||
| P value excluding never exposed | <0.01 | |||||
| Cumulative exposure, mg/m3-years | ||||||
| >0–0.39 | 1,113 | 6.6 | 1,128 | 5.4 | 1.15 | 1.04–1.27 |
| 0.4–1.09 | 1,221 | 7.2 | 1,120 | 5.3 | 1.33 | 1.21–1.47 |
| 1.1–2.39 | 1,231 | 7.3 | 1,122 | 5.4 | 1.29 | 1.17–1.42 |
| ≥2.4 | 1,358 | 8.0 | 1,118 | 5.3 | 1.45 | 1.31–1.60 |
| Test for trend, P value | <0.01 | |||||
| P value excluding never exposed | <0.01 | |||||
| Time since last exposure†, yr | ||||||
| <5 | 934 | 5.5 | 815 | 3.9 | 1.43 | 1.18–1.73 |
| 5–9 | 462 | 2.7 | 351 | 1.7 | 1.43 | 1.15–1.77 |
| 10–19 | 679 | 4.0 | 569 | 2.7 | 1.36 | 1.13–1.63 |
| 20–29 | 617 | 3.7 | 536 | 2.6 | 1.26 | 1.08–1.47 |
| 30–39 | 931 | 5.5 | 812 | 3.9 | 1.30 | 1.15–1.47 |
| >39 | 1,300 | 7.7 | 1,405 | 6.7 | 1.09 | 0.99–1.20 |
| Test for trend, P value | — | |||||
| P value excluding never exposed | 0.10 |
Definition of abbreviations: CI = confidence interval; OR = odds ratio.
*
OR adjusted for study, age group, sex, smoking (pack-years, time since quitting smoking), and list A jobs.
†
OR in “time since last exposure” is additionally adjusted for duration (continuous) of silica exposure. Trend test limited to exposed subjects.