Analyse d'une publication en épidémiologie

Exposure to air pollution was assigned using the CALINE4 dispersion model. Briefly, this model used Gaussian plume dispersion parameters with traffic data, emissions factors, and local meteorology to estimate exposure to the mixture of near-roadway pollutants at the homes of the children based on a model for the incremental increase in nitrogen oxides (NOx) above regional background levels. Exposures for freeway and non-freeway sources were assigned to the baseline address of the children.

Traffic exposure variables were based on the California Department of Transportation Functional Class (FC) data for the year 2000. The annual average daily traffic (AADT) volumes were conflated to the TeleAtlas road network. Traffic data were based on continuous measurements on freeways, highways, and some major arterials, and intermittent measurements within the previous three years on other major roads. The spatial pattern of traffic density changes slowly over time and the temporal period used here likely supplies a good representation of the longer-term traffic patterns around the subjects' homes for our study period. As described elsewhere, a kernel density function was estimated to smooth the influence of traffic around the home. This function down-weighted the influence of traffic exposures as a function of Euclidian distance away from the child's home. Based on previous evidence, traffic density was examined within 150 m of the home.