Using high-resolution residential greenspace measures in an urban environment to assess risks of allergy outcomes in children

Abstract

Despite reported health benefits of urban greenspace (gs), the epidemiological evidence is less clear for allergic disease. To address a limitation of previous research, we examined the associations of medium- and high-resolution residential gs measures and tree and/or grass canopies with allergic outcomes for children enrolled in the longitudinal cincinnati childhood allergy and air pollution study (ccaaps). We estimated residential gs based on 400 m radial buffers around participant addresses (n = 478) using the normalized differential vegetation index (ndvi) and land cover-derived urban greenspace (ugs) (tree and grass coverage, combined and separate) at 30 m and 1.5-2.5 m resolution, respectively. Associations between outdoor aeroallergen sensitization and allergic rhinitis at age 7 and residential gs measures at different exposure windows were examined using multivariable logistic regression models. A 10% increase in ugs-derived grass coverage was associated with an increased risk of sensitization to grass pollens (adjusted odds ratio [aor]: 1.27; 95% confidence interval = 1.02-1.58). For each 10% increase in ugs-derived tree canopy coverage, nonstatistically significant decreased odds were found for grass pollen sensitization, tree pollen sensitization, and sensitization to either (aor range = 0.87-0.94). Results similar in magnitude to ugs-tree canopy coverage were detected for ndvi and allergic sensitizations. High-resolution (down to 1.5 m) gs measures of grass- and tree-covered areas showed associations in opposite directions for different allergy outcomes. These data suggest that measures strongly correlated with tree canopy (e.g., ndvi) may be insufficient to detect health effects associated with proximity to different types of vegetation or help elucidate mechanisms related to specific gs exposure pathways.

Keywords: Allergic disease in children; Allergic rhinitis; Allergic sensitization; Normalized differential vegetation index (NDVI); Urban greenspace (UGS).

Fig. 1

Comparison of residential GS metrics: NDVI (30m resolution) and UGS (1.5m resolution) for a randomly selected location in the study area (Hamilton County).

Fig. 2

Residential GS metrics (400 m) and allergy outcomes at age 7: adjusted odds ratios and 95% CIs. Models are adjusted for the following covariates: race, sex, environmental tobacco smoke exposure, exposure to traffic-related air pollution, mother’s education (7 years), and neighborhood SES (7 years).