Assessing the Health Impact of Formaldehyde Exposure from Fires across North America

Formaldehyde (HCHO) is a significant outdoor air pollutant linked to cancer and non-carcinogenic health risks. With biomass burning as a primary HCHO source—both from direct emissions and secondary formation via volatile organic compound (VOC) precursors—our study tackles the health impact of HCHO exposure from fires. Due to the sparse surface HCHO measurements and uncertainties in the standard TROPOMI HCHO column data, we improve the TROPOMI HCHO retrieval by enhancing a priori profiles, explicitly accounting for aerosol impacts, and adjusting cloud radiance calculations. The new satellite HCHO retrieval is converted to surface concentrations using the GEOS-Chem chemical transport model. The new dataset is compared against standard retrievals and GEOS-Chem simulations and validated with Pandora measurements of HCHO columns and EPA AQS surface data, under scenarios with and without wildfire smoke. This approach allows us to use observation-based metric to identify regions with elevated HCHO concentrations during recent North American fire events, indicating potential acute health risks. Additionally, we assess the annual average HCHO levels to evaluate long-term exposure risks.