Abstract
Wildfires are a large source of air pollutants, including ozone (O3) and particulate matter (PM), that degrade air quality, and, as a result, cause health concerns. Several studies have reported the public health burden in neighborhoods near the source of wildfires; however, the exposure and associated health impacts to distant communities from the long-range transport of wildfire pollutants have not received as much attention. Our study investigated the ozone and PM2.5 concentrations attributed to the 2019 Woodbury and Mountain Fires in Arizona, as well as the identification of the populations exposed to concentrations surpassing Environmental Protection Agency (EPA) and the World Health Organization (WHO) air quality standards. The FINN model (Fire Inventory from the National Center of Atmospheric Research (NCAR) provided estimates of daily fire emissions for pollutants that were then input into a chemical transport model, CAM-CHEM (Community Atmosphere Model with Chemistry) to predict the evolution of secondary pollutants, including ozone and compounds that contribute to PM concentrations. The MUSICA-V0 configuration of the CAM-CHEM was run with wildfire emissions and a second time without them, to evaluate the impact of wildfire emissions alone on air quality. Additionally, the United States 2020 Census tracts were used to identify the populations exposed locally and distantly. It was found that both fires increased PM2.5 and O3 concentrations. Locally, both pollutants peaked above EPA and WHO guidelines; however, only long-range transported ozone concentrations surpassed air quality guidelines in distant populations. The quantified populations exposed to such levels due to the Woodbury Fire was an average of 88,000 people and 200,000 for the Mountain Fire. Understanding the extent to which wildfire emissions contribute to pollutant concentrations that exceed air quality guideline and pinpointing the vulnerable populations affected is of great importance for decision-making to keep people safe since, with a warmer climate, wildfires are expected to be more common.