Public Health in the Rockies 2026

Background/Purpose: Urban heat islands accelerate ground-level ozone formation through photochemical reactions, creating compound exposures that increase asthma emergency visits by 6–8% per 1°C temperature rise. This study examines how surface temperature, ozone, and built environment factors jointly drive asthma prevalence across New York City.

Methods: Asthma prevalence for 2,071 Census Tracts was obtained from the CDC 500 Cities database. Fifteen indicators were integrated — including spring and winter land surface temperature (Landsat), ozone concentration, building density, land use mix, employment accessibility, food environment access, income, car ownership, and race/ethnicity. Ordinary Least Squares (OLS) and Multiscale Geographically Weighted Regression (MGWR) captured spatial heterogeneity across scales. XGBoost-SHAP analysis identified non-linear predictor importance and interaction effects beyond the capacity of regression models.

Results: MGWR substantially outperformed OLS (R²≈0.90 vs. 0.47), confirming significant spatial non-stationarity in the built and social environmental drivers of asthma prevalence. correlation analysis indicating significant seasonal variation in the thermal environment's effect on asthma risk. MGWR assigns each predictor its own optimal bandwidth; smaller bandwidths indicate more localized effects. High-income proportion was the strongest factor (bandwidth=56, most localized), while car-free household proportion showed the strongest positive association with asthma (bandwidth=2,000, city-wide). Black/non-Hispanic population share significantly elevated asthma burden at a meso-scale (bandwidth = 500), reflecting persistent spatial inequities linked to historical residential segregation. Preliminary SHAP analysis further identified non-linear threshold effects, where asthma risk accelerates significantly above critical ozone concentration levels.

Implications: Heat and ozone co-exposure create spatially concentrated asthma disparities in low-income, minority neighborhoods. MGWR and SHAP together pinpoint where cooling infrastructure, street greening, and transit interventions can most effectively reduce asthma burden.