Short-term effects of various ozone metrics on cardiopulmonary function in chronic obstructive pulmonary disease patients: Results from a panel study in Beijing, China

Background Short-term exposure to ambient air pollution has been associated with lower pulmonary function and higher blood pressure (BP). However, controversy remains regarding the relationship between ambient multiple daily ozone (O₃) metrics and cardiopulmonary health outcomes, especially in the developing countries. Objectives To investigate and compare the short-term effects of various O₃ metrics on pulmonary function, fractional exhaled nitric oxide (FeNO) and BP in a panel study of COPD patients. Methods We measured pulmonary function, FeNO and BP repeatedly in a total of 43 patients with COPD for 215 home visits. Daily hourly ambient O₃ concentrations were obtained from central-monitoring stations close to subject residences. We calculated various O₃ metrics [daily 1-h maximum (O₃-1 h max), maximum 8-h average (O₃-8 h max) and 24-h average (O₃-24 h avg)] based on the hourly data. Daily indoor O₃ concentrations were estimated based on estimated indoor/outdoor O₃ ratios. Linear mixed-effects models were used to estimate associations of various O₃ metrics with cardiopulmonary function variables. Results An interquartile range (IQR) increase in ambient O₃-8 h max (80.5 μg/m³, 5-d) was associated with a 5.9% (95%CI: −11.0%, −0.7%) reduction in forced expiratory volume in 1 s (FEV₁) and a 6.2% (95%CI: −10.9%, −1.5%) reduction in peak expiratory flow (PEF). However, there were no significant negative associations between ambient O₃-1 h max, O₃-24 h avg and FEV₁, PEF. An IQR increase in ambient O₃-1 h max (85.3 μg/m³, 6-d) was associated with a 6.7 mmHg (95%CI: 0.7, 12.7) increase in systolic BP. The estimated indoor O₃ were still significantly associated with reduction of FEV₁ and PEF. No significant associations were found between various O₃ metrics and FeNO. Conclusions Our results provide clues for the adverse cardiopulmonary effects associated with various O₃ metrics in COPD patients and highlight that O₃-8 h max was more closely associated with respiratory health variables. O₃ exposure can pose threat to respiratory health with pollution level lower than the national O₃ standard in Beijing, China.