A Special Report of the Institute's Panel on the Health Effects of Traffic-Related Air Pollution. This report is the most comprehensive and systematic review to date of the scientific literature on emissions, exposure, and health effects from traffic-related air pollution. It includes conclusions about the populations exposed around major roads, the associations between exposure to air pollution from traffic and human health, and important remaining data gaps. Compared with the initial pre-print version released in May 2009, this final version has undergone data verification and editorial changes; however, the overall conclusions did not change.