Science Inventory

Evolution of Reactive Organic Compounds and Their Potential Health Risk in Wildfire Smoke

Citation:

Pye, H., L. Xu, B. Henderson, D. Pagonis, P. Campuzano-Jost, H. Guo, J. Jimenez, Christine Allen, N. Skipper, H. Halliday, Ben Murphy, E. D'Ambro, P. Wennberg, B. Place, F. Wiser, V. McNeill, E. Apel, D. Blake, M. Coggon, J. Crounse, J. Gilman, G. Gkatzelis, T. Hanisco, G. Huey, J. Katich, A. Lamplugh, J. Lindaas, J. Peischl, J. St. Clair, C. Warneke, G. Wolfe, AND C. Womack. Evolution of Reactive Organic Compounds and Their Potential Health Risk in Wildfire Smoke. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 58(44):19785–19796, (2024). https://doi.org/10.1021/acs.est.4c06187

Impact/Purpose:

Fires emit criteria pollutants and hazardous air pollutants with implications for inhalation health risk. This work develops a complete characterization of reactive organic carbon (non-methane organic gases and organic aerosol) and its potential for cancer and noncancer risk due to long-term exposure to fire smoke. This work provides insight into whether gas-phase hazardous air pollutants or organic aerosol have the larger potential for risk which has implications for how to mitigate the impacts of fire smoke. In addition, this work suggests current operational inventories should be updated to better reflect emissions an enable improved model predictions.

Description:

Wildfires are an increasing source of emissions into the air, with health effects modulated by the abundance and toxicity of individual species. In this work, we estimate reactive organic compounds (ROC) in western U.S. wildland forest fire smoke using a combination of observations from the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) field campaign and predictions from the Community Multiscale Air Quality (CMAQ) model. Standard emission inventory methods capture 40–45% of the estimated ROC mass emitted, with estimates of primary organic aerosol particularly low (5–8×). Downwind, gas-phase species abundances in molar units reflect the production of fragmentation products such as formaldehyde and methanol. Mass-based units emphasize larger compounds, which tend to be unidentified at an individual species level, are less volatile, and are typically not measured in the gas phase. Fire emissions are estimated to total 1250 ± 60 g·C of ROC per kg·C of CO, implying as much carbon is emitted as ROC as is emitted as CO. Particulate ROC has the potential to dominate the cancer and noncancer risk of long-term exposure to inhaled smoke, and better constraining these estimates will require information on the toxicity of particulate ROC from forest fires.