Comparing ozone metrics on associations with outpatient visits for respiratory diseases in Taipei Metropolitan area

This study reported cumulative 6-day (lag 0–5 days) relative risks (RR) and confidence intervals (CI) of daily outpatient visits for total respiratory disease (RD), asthma, and chronic airway obstruction not otherwise classified (CAO) associated with three ozone metrics (daily 1-h maximum (O3,1hmax), 8-h average maximum (O3,8hmax), 24-h average (O3,24havg)), and an alternative oxidant indicator (Ox) in Taipei Metropolitan, using distributed lag non-linear models after controlling for potential confounders. The Ox showed the strongest association with outpatient visits for total RD (RR = 1.10, 95% CI: 1.10, 1.11) and asthma (RR = 1.18, 95% CI: 1.00, 1.39) in the cold season. The O3,24havg appeared to be the optimal ozone metric associating with total RD than O3,1hmax and O3,8hmax based on model selection. In conclusion, outpatient visits for total RD associated with ozone vary with ozone metrics, disease and season. -- Highlights: ► The health risk of ozone varied by RD type and by the ozone metrics applied. ► O3,24havg was a better metric to associate with outpatient visits of total RD. ► Ox most correlated with outpatient visits for total RD in the cold season. -- The O3,24havg was a better metric than O3,1hmax and O3,8hmax to associate with outpatient visits of total respiratory diseases