The impact of PM2.5 on lung function in adults with asthma.

To conduct a systematic review of the literature and assess the effect of PM2.5 (particulate matter with diameter <2.5 μm) exposure on lung function in adults with asthma. We searched all literature published between 1 January 2010 and 26 March 2019 in the EMBASE, PubMed, Cochrane Central Library, Chinese National Knowledge Infrastructure (CNKI), Wanfang and Chinese Biomedical Literature (CBM) databases. The studies were assessed for analytic methods, risk of bias and results of statistical analysis. The selected studies all had a low or moderate risk of bias. Overall, PM2.5 exposure was positively associated with a decrease in forced expiratory volume in 1 sec (FEV)/forced vital capacity (FVC) in adults with asthma (standardised mean difference 0.20, 95% CI 0.02-0.38; = 0.03). We observed a negative correlation between PM2.5 exposure and FEV/FVC in patients with asthma. Our meta-analysis provides evidence suggesting that PM2.5 is a risk factor for acute asthma exacerbation in adults.