Abstract
BACKGROUND: Physical activity (PA) increases a person's inhalation of air pollutants due to greater ventilation, possibly leading to larger adverse health effects. This study aims to investigate the combined effects of long-term exposure to fine particulate matter (PM(2.5)) and habitual PA on lung function in adults. METHODS: This was a longitudinal cohort study that included 278,065 Taiwan residents with an age of 20 years old or above who joined a standard medical screening programme between 2001 and 2014. Each participant received at least one medical examination (including spirometric, blood, and urinary tests and a standard self-administered questionnaire survey) during the study period. We estimated the 2-year average PM(2.5) concentrations at each participant's address using a new physical model based on observational data. Information on the participants' PA was collected using the standard self-administrated questionnaire. Generalised linear mixed models were used to investigate the combined effects of PM(2.5) and PA on pulmonary function. We also performed stratified analyses by different levels of PM(2.5) exposure and habitual PA. RESULTS: Each 10 MET-h increase in PA was associated with a higher level of 0.20%, 0.16%, and 0.19% in forced vital capacity (FVC), forced expiratory volume in the first second (FEV(1)), and maximum mid-expiratory flow (MMEF), respectively, after adjusting for PM(2.5) exposure and a wide range of covariates including age, sex education, body mass index, lifestyles, and health conditions. Each 10 μg/m(3) increase in PM(2.5) was associated with a lower FVC, FEV(1), and MMEF (2.43%, 2.78% and 3.10%, respectively). Negative interactions were observed, and PM(2.5) exposure was associated with a greater reduction in lung function among the participants with higher PA levels. CONCLUSIONS: We found significant negative interaction effects between long-term exposure to PM(2.5) and habitual PA, suggesting that the increased intake of PM(2.5) due to PA may attenuate the benefits of habitual PA on lung function. However, the PA benefits generally remained stable at different stratum of PM(2.5) in the stratified analyses, and habitual PA may still be recommended to people residing in relatively polluted regions.