Spatial Variations of PM2.5 in Baltimore: Leveraging In Situ and Satellite-Based Measurements

Exposure to PM2.5 poses significant health risks, including the aggravation of asthma and increased cardiovascular and respiratory morbidity and mortality. Accurately quantifying the spatial distribution of PM2.5 is critical for protecting public health and ensuring environmental equity. However, our understanding of the spatial variability in PM2.5 within cities remains limited, making it challenging to identify and support vulnerable populations. Here, we use regulatory monitors from the Maryland Department of the Environment, a network of low-cost multipollutant monitors, and three satellite-based estimates to quantify the PM2.5 variability within Baltimore, MD. In situ observations show strong seasonality in city-averaged PM2.5, with the highest concentrations in Winter and Summer, but the spatial standard deviation of monthly averaged in-situ PM2.5 averages less than 1 μg/m3 over October 2019–2023. All satellite products have similar seasonality but overestimate the intraurban spatial variability compared to in-situ observations. This overestimation of spatial variability suggests caution when using satellite estimates at intraurban scales to examine disparities in urban PM2.5 pollution or to isolate urban sources.