Long-Term Personal Exposure to Traffic and Coronary Calcification

Background Epidemiological evidence suggests that long-term exposure to particulate matter (PM) air pollution accelerates atherogenesis and increases cardiopulmonary mortality [1;2]. We examined the relationship between long-term personal exposure to traffic, a major source of urban air pollution, and the degree of coronary artery calcification (CAC), controlling for major risk factors for arteriosclerosis and background PM air pollution. Methods We used baseline data from the German Heinz Nixdorf Recall study, an ongoing population-based, prospective cohort study of 4814 inhabitants of the Rhein-Ruhr area [3]. Participants ´ addresses were geocoded with a geographic information system (GIS). To assess personal long-term traffic exposure, the major source of ambient ultrafine particles (UFP, < 100 nm), distances between residence and major roads, namely autobahn (mean daily vehicle count>30,000) and federal highways (mean daily vehicle count>10,000 to <30,000) were calculated with the GIS. Distance to major roads is a useful surrogate for UFP-exposure, because UFP exhibit a steep decline in number concentration with increasing distance from major motorways [4]. Annual mean values for PM2.5 mass concentration on a spatial scale of 1 km were estimated with the EURAD-model for the year 2002 (midpoint of baseline examination) and assigned to each address [5]. The main outcome was the degree of coronary artery calcification (CAC), assessed quantitatively by electron-beam computer tomography [6]. CAC is a highly reproducible and accurate measure of clinical and subclinical coronary atherosclerosis that correlates well with cardiovascular risk factors and clinical events. We evaluated the association between the logarithm of proximity to major roads and log(CAC+1) with linear regression, controlling for background PM2.5 and individual level risk factors fo