Projected increases in wildfires may challenge regulatory curtailment of PM_2.5 over the eastern US by 2050

Anthropogenic contribution to the overall fine particulate matter (PM2.5) concentrations has been declining sharply in North America. In contrast, a steep rise in wildfire-induced air pollution events with recent warming is evident in the region. Here, based on coupled fire-climate-ecosystem model simulations, summertime wildfire-induced PM2.5 concentrations are projected to nearly double in North America by the mid-21st century compared to the present. More strikingly, the projected enhancement in fire-induced PM2.5 (similar to 1-2 mu g m(-3)) and its contribution (similar to 15 %-20 %) to the total PM2.5 are distinctively significant in the eastern US. This can be attributed to downwind transport of smoke from future enhancement of wildfires in North America to the eastern US and associated positive climatic feedback on PM2.5, i.e., perturbations in circulation, atmospheric stability, and precipitation. Therefore, the anticipated reductions in PM2.5 from regulatory controls on anthropogenic emissions could be significantly compromised in the future in the densely populated eastern US.