This article is a commentary on the following study: "Recent exposure to particulate matter and C-reactive protein concentration in the Multi-Ethnic Study of Atherosclerosis". Diez Roux AV, Auchincloss AH, Astor B, Barr RG, Cushman M, Dvonch T, Jacobs DR Jr, Kaufman J, Lin X, and Samson P. Am J Epidemiol. 2006;164:437-48.