RR (95% CI) of COPD by quartiles of cumulative organic dust exposure among 4032 farm workers (n=1911) and wood industry workers (n=2121) with individual smoking information (n=65 464 person-years)
| Organic dust exposure | COPD cases (n) | RR crude | (95% CI) | RR adjusted* | (95% CI* | RR adjusted† | (95% CI†) |
| Low (0.06–6.05 mg/m3-year) (n=16 366 py) | 18 | 1 | 1 | 1 | |||
| Intermediate-low (>6.05–12.39 mg/m3-year) (n=16 366 py) | 12 | 0.67 | (0.32 to 1.38) | 0.91 | (0.43 to 1.91) | 0.90 | (0.43 to 1.89) |
| Intermediate-high (>12.39-21-35 mg/m3-year) (n=16 366 py) | <5 | 0.22 | (0.08 to 0.66) | 0.33 | (0.11 to 0.98) | 0.34 | (0.11 to 1.02) |
| High (>21.35–107.87 mg/m3-year) (n=16 366 py) | 11 | 0.61 | (0.29 to 1.29) | 0.67 | (0.31 to 1.45) | 0.73 | (0.33 to 1.59) |
| Per mg/m3-year‡ | 0.99 | (0.96 to 1.01) | 0.99 | (0.97 to 1.01) | 0.99 | (0.97 to 1.02) |
*Adjustment for age (continuous), calendar year and sex.
†Adjustment for age (continuous), calendar year, sex and ever smoking at baseline.
‡ Continuous cumulative organic dust exposure.
COPD, chronic obstructive pulmonary disease; py, person years.