The role of vegetation in mitigating air quality impacts from traffic emissions

Researchers and policy makers met in April 2010 for an EPA-sponsored workshop to discuss the current scientific understanding of how vegetative barriers along roads affect air pollution. This document is a brief summary of the workshop and the state of the science at that time. It describes mixed results from field work, wind-tunnel studies, and computational fluid dynamic models: some studies showed improved levels of carbon monoxide and some categories of small particulate matter, other studies suggested that the presence of a vegetative barrier could result in higher levels of pollutants behind it than would otherwise have been present. Policy considerations and next research steps are described. A 22-entry bibliography of research on the topic is included.