Abstract
Many epidemiological studies examining long-term health effects of exposure to air pollutants have characterized exposure by the outdoor air concentrations at sites that may be distant to subjects’ residences at different points in time. The temporal and spatial mobility of subjects and the spatial scale of exposure assessment could thus lead to misclassification in the cumulative exposure estimation. This paper 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. 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-year period prior to that for which the health events are to be detected. Our conceptual framework is both flexible and convenient for the needs of different epidemiological study designs.
Highlights
We present an overview of exposure assessment in the exploration of long-term effects in epidemiological studies
We propose a conceptual framework for the retrospective assessment of air pollution, including two components: (1)
Other models with similar spatial performance can be used along the same lines. This conceptual framework was designed for ecological approaches, as in the study we are undertaking on breast cancer, but we are confident that the concept is adaptable to other study designs; for instance, examining annual air pollution concentrations of cohort participants’ census blocks rather than zip codes [7]
Summary
The World Health Organization has estimated that deaths attributed to outdoor air pollution are predominantly due to ischemic heart diseases and strokes (80%), followed by chronic obstructive pulmonary diseases or acute lower respiratory infections (14%) and lung cancer (6%) [1]. No epidemiological study investigating the health effects of long-term exposure to air pollution has accounted for residential mobility in assessing cumulative exposure at a fine spatial scale. (iv) retrospective reconstitution of NO2 concentrations at a fine spatial scale (NO2 has been chosen as the index pollutant because its spatial variability is higher than in many other air pollutants); and a novel approach to assigning time-relevant exposure estimates at the census block level, using all available data on residential mobility throughout the 10-to 20-year period prior to that for which the health events are to be detected. We discuss the need for this conceptual framework, and its subsequent value
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