Associations between Short-term Exposure to Ambient PM_2.5 and Lung Function in Undiagnosed COPD Patients

Objectives To analyze the associations between short-term exposure to ambient PM_2.5 and lung function in undiagnosed COPD population, and to provide a scientific foundation for the protection against air pollution.

Methods Subjects were undiagnosed COPD population screened by lung function test. In January, March, August, and October of 2018, 28 subjects were tested repeatedly. For each time, lung function testing, questionnaire survey, and the PM_2.5 mass concentration monitoring for 5 days before each lung function test were conducted. Mixed effect model was used to analyze the associations between PM_2.5 and lung function. The lag effect of PM_2.5 mass concentration on lung function was considered, and the lag0~lag4 PM_2.5 mass concentration was used in the model.

Results The maximum daily PM_2.5 mass concentration was 250.46 μg/m³. The result of one-day lag effect showed that FEV₁, MEF₂₅, MEF₅₀, and FEV₁/FVC were significantly associated with the mass concentration of PM_2.5 in lag01. As PM_2.5 mass concentration was increased by 10 μg/m³, FEV₁, MEF₂₅, MEF₅₀, and FEV₁/FVC were decreased by 0.05 L, 0.03 L/s, 0.10 L/s, and 1.09%, respectively. FVC, MEF₇₅, and PEF were not associated with PM_2.5 mass concentration. The moving average lag effect showed that only MEF₅₀ was significantly associated with PM_2.5 mass concentration in lag01 (P < 0.1). As PM_2.5 mass was increased by 10 μg/m³, MEF₅₀ was decreased by 0.07 L/s.

Conclusions Ambient air PM_2.5 can lead to the decline of pulmonary ventilation function indicators in undiagnosed COPD patients, and it is necessary to pay attention to the protection of this group of people against the heavy pollution weather. The impact of air pollution on small airway deserve more attention.