Within-City Variation in Ambient Carbon Monoxide Concentrations: Leveraging Low-Cost Monitors in a Spatiotemporal...

Based on human and animal experimental studies, exposure to ambient carbon monoxide (CO) may be associated with cardiovascular disease outcomes, but epidemiological evidence of this link is limited. The number and distribution of ground-level regulatory agency monitors are insufficient to characterize fine-scale variations in CO concentrations.

To develop a daily, high-resolution ambient CO exposure prediction model at the city scale.

We developed a CO prediction model in Baltimore, Maryland, based on a spatiotemporal statistical algorithm with regulatory agency monitoring data and measurements from calibrated low-cost gas monitors. We also evaluated the contribution of three novel parameters to model performance: high-resolution meteorological data, satellite remote sensing data, and copollutant (${\mathrm{PM}}_{2.5}$, ${\mathrm{NO}}_2$, and ${\mathrm{NO}}_x$) concentrations.

The CO model had spatial cross-validation (CV) $R^2$ and root-mean-square error (RMSE) of $0.70\text{\hspace{0.17em}and\hspace{0.17em}}0.02\text{\hspace{0.17em}parts per million}$ (ppm), respectively; the model had temporal CV $R^2$ and RMSE of 0.61 and $0.04\text{\hspace{0.17em}ppm}$, respectively. The predictions revealed spatially resolved CO hot spots associated with population, traffic, and other nonroad emission sources (e.g., railroads and airport), as well as sharp concentration decreases within short distances from primary roads.

The three novel parameters did not substantially improve model performance, suggesting that, on its own, our spatiotemporal modeling framework based on geographic features was reliable and robust. As low-cost air monitors become increasingly available, this approach to CO concentration modeling can be generalized to resource-restricted environments to facilitate comprehensive epidemiological research. https://doi.org/10.1289/EHP10889.