Regression model for chronic airflow limitation at follow-up#
| Variables¶ | Prevalence ratio | 95% CI | p-value |
| Only pre-baseline ozone gassings | 4.3 | 1.2–15.7 | 0.03 |
| Both pre-baseline and interval ozone gassings | 5.5 | 1.1–28.0 | 0.04 |
| Only interval ozone gassings | 1.8 | 0.2–16.7 | 0.59 |
| ClO2/SO2 gassings | 0.8 | 0.2–2.8 | 0.75 |
| Bleachery workers, no gassings | 1.7 | 0.4–6.5 | 0.45 |
| Female | 3.4 | 1.1–9.8 | 0.03 |
| Current smoker+ | 2.9 | 0.9–9.9 | 0.08 |
| Former smoker+ | 1.5 | 0.5–4.3 | 0.46 |
CI: confidence interval; ClO2: chlorine dioxide; SO2: sulphur dioxide. #: Chronic airflow limitation was defined as forced expiratory volume in one second/forced vital capacity less than the lower limit of normal; ¶: work-related exposure classes have a common comparison group in the paper mill workers; +: smoking status was at follow-up.