A Conceptual Framework for the Assessment of Cumulative Exposure to Air Pollution at a Fine Spatial Scale

Abstract

Introduction In many epidemiological studies, the temporal and spatial mobility of subjects and the spatial scale of exposure assessment could lead to misclassification in the cumulative exposure estimation. This study is attempts to fill the gap regarding cumulative exposure assessment to air pollution at a fine spatial scale in epidemiological studies investigating long-term health effects. Methods We propose a conceptual framework showing how major difficulties in cumulative long-term exposure assessment could be surmounted. We then illustrate this conceptual model on the case of exposure to NO2 following two steps: i) retrospective reconstitution of NO2 concentrations at a fine spatial scale; and ii) a novel approach to assigning the time-relevant exposure estimates at the census block level, using all available data on residential mobility throughout a 10- to 20- years period prior to that for which the health events are to be detected. Results Using French data, results showed a regular decrease trend in NO2 concentrations at the census block level between 2002 and 2012 in Paris, with 61.0µg/m3 in 2003 and 51.2 µg/m3 in 2012. When including the mobility matrix, constructed from the national census database, in the estimation of cumulative NO2 exposures, the relative difference between these two exposure levels (with and without residential mobility) across the 20 arrondissements of Paris varies between 2.7 to 5.6 µg/m3 (mobility rate equal to 8.8% versus 19%). Conclusion Our finding revealed significant differences between population exposure level with and without taking into account residential mobility over a 5-year period and suggest that this difference which is attributed to residential mobility may change the result of epidemiological studies. The conceptual framework describe in this study is both flexible and convenient for the needs of different epidemiological study designs.