Health Risk Implications of Volatile Organic Compounds in Wildfire Smoke During the 2019 FIREX‐AQ Campaign and Beyond

Fire Influence on Regional to Global Environments and Air Quality was a NOAA/NASA collaborative campaign conducted during the summer of 2019. The objectives included identifying and quantifying wildfire composition, smoke evolution, and climate and health impacts of wildfires and agricultural fires in the United States. Ground based mobile sampling via sorbent tubes occurred at the Nethker and Williams Flats fires (2019) and Chief Timothy and Whitetail Loop fires (2020) in Idaho and Washington. Air samples were analyzed through thermal desorption‐gas chromatography‐mass spectrometry for a variety of volatile organic compounds to elucidate both composition and health impacts. Benzene, toluene, ethylbenzene, xylenes, butenes, phenol, isoprene and pinenes were observed in the wildfire smoke, with benzene ranging from 0.04 to 25 ppbv. Health risk was assessed for each fire by determining sub‐chronic (wildfire event) and projected chronic inhalation risk exposure from benzene, a carcinogen, as well as other non‐carcinogenic compounds including toluene, ethylbenzene, xylenes, and hexane. The cancer risk of benzene from sub‐chronic exposure was 1 extra cancer per million people and ranged from 1 to 19 extra cancers per million people for the projected chronic scenarios, compared to a background level of 1 extra cancer per million people. The hazard index of non‐carcinogenic compounds was less than one for all scenarios and wildfires sampled, which was considered low risk for non‐cancer health events. Plain Language Summary Wildfires have been growing in size in the western United States (US) and negatively impacting the air quality of the region. Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) was a US government funded campaign conducted during the summer of 2019. The main goals included identifying and quantifying wildfire smoke composition and climate and health impacts of wildfires and agricultural fires in the US. Ground based air sampling occurred at the Nethker and Williams Flats fires (2019) during FIREX‐AQ and afterward at Chief Timothy and Whitetail Loop fires (2020), located in Idaho and Washington states. Air samples were analyzed in the laboratory for 106 gases and air toxics to determine the type of compounds present and their concentrations. Health risk was assessed for each fire by determining inhalation exposure from benzene, an air toxic that can cause cancer, as well as non‐cancer causing compounds. The cancer risk