Accounting for Mobility in Air Pollution Exposure Estimates in Studies on Long-Term Health Effects.

introductionLarge-scale epidemiological studies investigating long-term health effects of air pollution can typically only consider the residential locations of the participants, thereby ignoring the space-time-activity patterns that likely influence total exposure. People are mobile and can be exposed to considerably different levels of air pollution or air pollution mixtures when inside versus outside, commuting, recreating, or working. Neglecting these mechanisms in exposure assessment may lead to incorrect distributions of exposure over the population, which may, subsequently, lead to incorrect exposure-health relations in epidemiological studies. In this study, we investigated whether a more sophisticated mobility-enhanced exposure assessment would lead to different exposure predictions and health effect estimates compared with using a residential-based exposure.

methodsAgent-based modeling (ABM

resultsWe successfully developed mobility-enhanced exposures for over 3 million participants, including an assessment of uncertainty. We found a good agreement between exposures estimated with the app and the GPS tracker, supporting the scalability of the approach. We evaluated the ABMs with GPS and time-activity data collected independently in tracking campaigns that included almost 700 participants from selected areas in the two countries. For these participants, the exposures based on GPS measurements versus those derived from ABM showed a moderate to good agreement (R

conclusionsOur results suggest that the assessment of air pollution exposure at the residential address in epidemiological studies generally does not lead to substantial bias in health effects estimates. If time-activity patterns in other study areas differ greatly from the patterns analyzed in our study, differences between residential and activity-enhanced exposures may be larger. Despite the good agreement between residential and work locations, exposure research should continue to strive toward improving exposure assessment in large-scale epidemiological studies to minimize exposure misclassification.