Background Traffic congestion is a significant issue in urban areas in the United States and around the world. Previous analyses have estimated the economic costs of congestion, related to fuel and time wasted, but few have quantified the public health impacts or determined how these impacts compare in magnitude to the economic costs. Moreover, the relative magnitudes of economic and public health impacts of congestion would be expected to vary significantly across urban areas, as a function of road infrastructure, population density, and atmospheric conditions influencing pollutant formation, but this variability has not been explored. Methods In this study, we evaluate the public health impacts of ambient exposures to fine particulate matter (PM 2.5) concentrations associated with a business-as-usual scenario of predicted traffic congestion. We evaluate 83 individual urban areas using traffic demand models to estimate the degree of congestion in each area from 2000 to 2030. We link traffic volume and speed data with the MOBILE6 model to characterize emissions of PM 2.5 and particle precursors attributable to congestion, and we use a source-receptor matrix to evaluate the impact of these emissions on ambient PM 2.5 concentrations. Marginal concentration changes are related to a concentration-response function for mortality, with a value of statistical life approach used to monetize the impacts. Results We estimate that the monetized value of PM 2.5-related mortality attributable to congestion in these 83 cities in 2000 was approximately 31billion(2007dollars),ascomparedwithavalueoftimeandfuelwastedof 60 billion. In future years, the economic impacts grow (to over 100billionin2030)whilethepublichealthimpactsdecreaseto 13 billion in 2020 before increasing to 17billionin2030,givenincreasingpopulationandcongestionbutloweremissionspervehicle.Acrosscitiesandyears,thepublichealthimpactsrangefrommorethananorderofmagnitudelesstoinexcessoftheeconomicimpacts.ConclusionsOuranalysesindicatethatthepublichealthimpactsofcongestionmaybesignificantenoughinmagnitude,atleastinsomeurbanareas,tobeconsideredinfutureevaluationsofthebenefitsofpoliciestomitigatecongestion.