Cycling to work has been promoted as a green commute in many countries because of its reduced congestion relative to that of cars and its reduced environmental impact on air pollution. However, cyclists might be exposed to higher air pollution, causing adverse health effects. The aim of this thesis was to assess the impact of air pollution exposure on lung function while cycling in traffic. Twenty-five healthy adults in total cycled on a specified route in each of three Chinese cities during four periods of a day. Lung function, real-time particulate matter concentration, and ambient concentration of other pollutants were measured. Mixed-effect models were applied to estimate the impact of short-term air pollution exposure on participants’ lung function during cycling. The results indicated that cyclists’ exposure to fine particles was significantly associated with reduced lung function. Fine particles compared to other pollutants are more harmful to cyclists’ respiratory health.