Background:The effects of near-road pollution on lung function in China have not been well studied.We aimed to investigate the effects of long-term exposure to traffic-related air pollution on lung function,airway inflammation,and respiratory symptoms.Methods:We enrolled 1003 residents aged 57.96 ± 8.99 years living in the Shichahai Community in Beijing.Distances between home addresses and the nearest major roads were measured to calculate home-road distance.We used the distance categories 1,2,and 3,representing ＜100 m,100-200 m,and ＞200 m,respectively,as the dose indicator for traffic-related air pollution exposure.Lung function,exhaled breath condensate (EBC) pH,and interleukin 6 levels were measured.As a follow-up,398 participants had a second lung function assessment about 3 years later,and lung function decline was also examined as an outcome.We used regression analysis to assess the impacts of home-road distance on lung function and respiratory symptoms.As the EBC biomarker data were not normally distributed,we performed correlation analysis between home-road distance categories and EBC biomarkers.Results:Participants living a shorter distance from major roads had lower percentage of predicted value of forced expiratory volume in 1 s (FEV1％-1.54,95％ confidence interval [CI]:-0.20 to-2.89).The odds ratio for chronic cough was 2.54 (95％ CI.:1.57-4.10) for category 1 and 1.97 (95％ CI.:1.16-3.37) for category 2,compared with category 3.EBC pH was positively correlated with road distance (rank correlation coefficient of Spearman [rs] =0.176,P ＜ 0.001).Conclusions:Long-term exposure to traffic-related air pollution in people who live near major roads in Beijing is associated with lower lung function,airway acidification,and a higher prevalence of chronic cough.EBC pH is a potential useful biomarker for evaluating air pollution exposure.