“ Survey on Beijing Metro Commuters’ PM2.5 Exposure in the Metro Cars, Protection Actions and Health Risk Estimate ”：With the public awareness of air pollution increased significantly in recent years, during the haze days, the percentage of the public go out wearing masks and use air purifiers indoor has been significantly increased. However, the air quality in public places such as the subway, there are relatively limited research on the potential health risk of air pollution in the subway to the passengers. This study examines the public awareness, protection behavior, PM2.5 exposure and willingness to pay for air pollution mitigation measures through questionnaire- based survey. The results show that the age, sex, income, educational level of the respondents and whether they have children are related to whether they are taking protective measures and whether they are buying protective equipment for air pollution. At the same time, PM2.5 concentration in subway cars were also monitored while conducting the survey, the results show that during the project period the subway PM2.5 concentrations were higher than the outdoor, with the average monitoring value of 143 µg/m3, and among the monitored subway lines there is obvious difference in terms of the PM2.5 level. The study estimates the long-term health risk of PM2.5 exposure in Beijing subway commuters by applying the Exposure- response Functions and Pope’s relevant empirical research data.