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 (O) metrics and cardiopulmonary health outcomes, especially in the developing countries.

Objectives: To investigate and compare the short-term effects of various O 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 O concentrations were obtained from central-monitoring stations close to subject residences. We calculated various O metrics [daily 1-h maximum (O-1 h max), maximum 8-h average (O-8 h max) and 24-h average (O-24 h avg)] based on the hourly data. Daily indoor O concentrations were estimated based on estimated indoor/outdoor O ratios. Linear mixed-effects models were used to estimate associations of various O metrics with cardiopulmonary function variables.

Results: An interquartile range (IQR) increase in ambient O-8 h max (80.5 μg/m, 5-d) was associated with a 5.9% (95%CI: -11.0%, -0.7%) reduction in forced expiratory volume in 1 s (FEV) 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 O-1 h max, O-24 h avg and FEV, PEF. An IQR increase in ambient O-1 h max (85.3 μg/m, 6-d) was associated with a 6.7 mmHg (95%CI: 0.7, 12.7) increase in systolic BP. The estimated indoor O were still significantly associated with reduction of FEV and PEF. No significant associations were found between various O metrics and FeNO.

Conclusions: Our results provide clues for the adverse cardiopulmonary effects associated with various O metrics in COPD patients and highlight that O-8 h max was more closely associated with respiratory health variables.