Over the past decade the evidence base linking air pollution, especially that derived from traffic to increased respiratory mortality and morbidity has expanded dramatically, with important multi-cohort studies in Europe, and new evidence from North America and the developing/industrialising nations of the world. The purpose of this research seminar is to review this enriched evidence base and to address a series of questions that have either remained unanswered over this period, or are contentious, with significant differences of opinion within the research community.