This article is a commentary on the following study: Hoek G, Brunekreef B, Goldbohm S, Fischer P, van den Brandt PA. Association between mortality and indicators of traffic-related air pollution in the Netherlands: a cohort study. Lancet. 2002 Oct 19;360(9341):1203-9. This study is the first of its kind conducted in Europe to investigate the long-term relationship between chronic exposure to urban air pollution and mortality. The cohort studied consists of older adults. This study highlights a relationship between living near a high-traffic road and mortality from cardiopulmonary causes. Beyond multi-source urban pollution, it is local traffic, as a source of pollution, that is clearly implicated. Nevertheless, the lack of a significant association between background pollution and mortality, the population studied, and the method used to estimate exposure make it difficult to apply these results to future studies estimating health impacts outside the Netherlands. (Excerpt from the article)