Fire heat affects the impacts of wildfires on air pollution in the United States

Conventional wisdom suggests that wildfires in the western United States (WUS) degrade air quality nationwide as a result of aerosol emissions and eastward transport. However, we found that heat produced by wildfires, a commonly neglected effect, can reduce fine particle concentrations (PM 2.5 ) in the eastern United States (EUS) by an amount comparable to the increases in the WUS during the fire season. This phenomenon arises from fire heat–induced convection in the WUS and subsequent downstream meteorological changes distant from fires. Enhanced wet deposition and weakened eastward transport of fire aerosols lower PM 2.5 levels in the EUS. Therefore, neglecting the effect of fire heat on PM 2.5 pollution leads to an overestimate of 1200 additional premature deaths and 3.3 billion USD in economic losses, particularly in the densely populated EUS.