This issue of Aerosol Science and Technology includes two peer-reviewed papers presented at the conference Transport and Air Pollution (TAP) 2009 held at Toulouse, France, between June 2–4, 2009. This conference was the seventeenth of a series of conferences organized since 1986 with the aim of assessing the scientific knowledge on air pollution due to emissions from transportation systems. Similarly to the other TAP conferences, discussions covered a wide spectrum of topics, from the charac- terization of atmospheric emissions from mobile engines, and their impact on air quality and on human health to the efficiency and acceptability of possible transport policies and mitigation measures to reduce both climate- and health-relevant emissions. However, the distinctive feature of this seventeenth edition was the special emphasis on airborne particulate matter that is now well recognized to be deleterious to human health.
