Estimated personal soot exposure is associated with acute myocardial infarction onset in a case-crossover study

The current study investigates the association of estimated personal exposure to traffic-related air pollution and acute myocardial infarction (AMI). Cases of AMI were interviewed in the Augsburg KORA Myocardial Infarction Registry from February 1999 through December 2003, and 960 AMI survivors were included in the analyses. The time-varying component of daily personal soot exposure (the temporally variable contribution due to the daily area level of exposure and daily personal activities) was estimated using a linear combination of estimated mean ambient soot concentration, time spent outdoors, and time spent in traffic. The association of soot exposure with AMI onset was estimated in a case-crossover analysis controlling for temperature and day of the week using conditional logistic regression analyses. Estimated personal soot exposure was associated with AMI (relative risk, 1.30 per 1.1 m(-1) × 10(-5) [95% confidence interval, 1.09-1.55]). Estimated ambient soot and measured ambient PM(2.5) particulate matter 2.5 µm and smaller in aerodynamic diameter were not significantly associated with AMI onset. Our results suggest that an increase in risk of AMI in association with personal soot exposure may be in great part due to the contribution of personal soot from individual times spent in traffic and individual times spent outdoors. As a consequence, estimates calculated based on measurements at urban background stations may be underestimations. Health effects of traffic-related air pollution may need to be updated, taking into account individual time spent in traffic and outdoors, to adequately protect the public.