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.