Sensitivity of estimated NO2-attributable pediatric asthma incidence to grid resolution and urbanicity

Abstract

Nitrogen dioxide (NO2) is a major urban air pollutant and is associated with new onset asthma among children worldwide. Since NO2 concentrations are spatially heterogeneous and correlated with population, the spatial resolution of concentration estimates and disease burden calculations could strongly influence the magnitude and spatial distribution of estimated NO2-attributable pediatric asthma (PA) cases. Here, we investigate the effect of spatial resolution of exposure and population data on estimated NO2 attributable PA incidence. We use epidemiologically derived health impact functions to estimate NO2-attributable asthma incidence for the U.S. and India, two countries with different degrees of urbanicity, using population and NO2 concentration estimates at 100 m resolution and aggregated to coarser spatial resolutions: 500 m, 1 km, 10 km, and 100 km. Estimated NO2-attributable PA burdens differ by <1% for resolutions of 100 m up to 1 km for both countries. However, performing the analysis at 10 km and 100 km results in 5% and 17% fewer new asthma cases among children in India and 6% and 32% fewer in the U.S., respectively. We performed a similar analysis for the 13 000 urban areas and present the results for the 500 most populated cities at 1 km and 10 km resolution, finding that the coarser resolution leads to lower estimated NO2-attributable asthma incidence in nearly all cities, especially for cities with smaller land areas. We conclude that 1 km spatial resolution is a good balance between accuracy and computational efficiency in estimating NO2-attributable asthma burdens at national and urban levels, and that coarser resolutions may result in underestimates.