Retrospective assessment of exposure to traffic air pollution using the ExTra index in the VESTA French epidemiological study

Abstract

This study applies a traffic exhaust air dispersion model (the ExTra index) to 403 children enrolled in a French multicentric case-control study, the VESTA study (Five [V] Epidemiological Studies on Transport and Asthma). The ExTra index (previously validated by our team) was used to assess lifelong average traffic-related air pollutant (TAP) concentrations (nitrogen oxides) children in the study were exposed to in front of their living places. ExTra index took into account traffic density, topographical parameters (building height, road and pavement width), weather conditions (wind direction and strength) and background pollution levels. Topographical and traffic data were collected, using a specific questionnaire for each home, school or nursery address, attended by children. The assessment of time-weighted NO x levels in front of the children's living places highlighted significant disparities: mean ExTra index values and share attributable to proximity traffic were, respectively, 70742 and 14722 mg/m 3 NO x equivalent NO 2 for the 403 children in our study. Not only would this diversity not have been revealed using urban background pollution data provided by air quality networks, it would have resulted in 40% of the children being misclassified with regard to their TAP exposure by underestimating it in half of the cases and overestimating it in the other half. Such errors of classification, which are highly prejudicial in epidemiology, argue strongly for the use of an index such as the ExTra, which enables TAP exposure to be reconstructed within the framework of retrospective or prospective epidemiological studies.

Land use regression modeling of intra-urban residential variability in multiple traffic-related air pollutants

“…We expected obstruction to modify PM or EC, in keeping with recent findings suggesting that roadside barriers reduce PM concentrations [ 32 ]. Though we did not expect to find this effect for a gaseous pollutant such as NO 2 , this result is supported by recent evidence that residential NO 2 concentrations differed significantly depending on whether the home faced onto the courtyard or street, after accounting for distance to road [ 33 ]. Our findings may also be in part related to our passive sampling approach (as an obstruction could reduce the face velocity on the sampler).…”

Traffic-related air pollution and development of allergic sensitization in children during the first 8 years of life

“…Similar results were obtained in a French study in which topographic and traffic characteristics of residences and nurseries/schools were found to be similar. 45 Furthermore, air pollution levels at the home address are highly relevant as exposure estimates in infancy because in Sweden children usually do not start day care before 12 months of age.…”

A longitudinal analysis of associations between traffic-related air pollution with asthma, allergies and sensitization in the GINIplus and LISAplus birth cohorts

“…Although we conducted several sensitivity analyses to reduce potential moving-related exposure misclassification and noted no changes in the results, it is possible that some exposure misclassification remains, especially at the older ages when children spend a larger proportion of their time at school. However, a Swedish and French study showed that exposures from traffic assessed at the home address are good approximations of those at schools, possibly because schools tend to be located in the close vicinity of homes ( Gruzieva et al, 2012 ; Reungoat et al, 2005 ). Additionally, a study conducted in the United States found little differences between time-weighted averages of diesel exposures estimated at all addresses where a child spent more than eight hours per week and those estimated only at the home address ( Ryan et al, 2008 ).…”