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

Abstract

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. 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. 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 (O3-1h max), maximum 8-h average (O3-8h max) and 24-h average (O3-24h 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. An interquartile range (IQR) increase in ambient O3-8h max (80.5μg/m3, 5-d) was associated with a 5.9% (95%CI:-11.0%,-0.7%) reduction in forced expiratory volume in 1s (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 O3-1h max, O3-24h avg and FEV1, PEF. An IQR increase in ambient O3-1h max (85.3μg/m3, 6-d) was associated with a 6.7mmHg (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. Our results provide clues for the adverse cardiopulmonary effects associated with various O3 metrics in COPD patients and highlight that O3-8h max was more closely associated with respiratory health variables.