Estimated Mortality and Morbidity Attributable to Smoke Plumes in the United States: Not Just a Western US Problem

As anthropogenic emissions continue to decline and emissions from landscape (wild, prescribed, and agricultural) fires increase across the coming century, the relative importance of landscape-fire smoke on air quality and health in the United States (US) will increase. Landscape fires are a large source of fine particulate matter (PM2.5), which has known negative impacts on human health. The seasonal and spatial distribution, particle composition, and co-emitted species in landscape-fire emissions are different from anthropogenic sources of PM2.5. The implications of landscape-fire emissions on the sub-national temporal and spatial distribution of health events and the relative health importance of specific pollutants within smoke are not well understood. We use a health impact assessment with observation-based smoke PM2.5 to determine the sub-national distribution of mortality and the sub-national and sub-annual distribution of asthma morbidity attributable to US smoke PM2.5 from 2006 to 2018. We estimate disability-adjusted life years (DALYs) for PM2.5 and 18 gas-phase hazardous air pollutants (HAPs) in smoke. Although the majority of large landscape fires occur in the western US, we find the majority of mortality (74%) and asthma morbidity (on average 75% across 2006-2018) attributable to smoke PM2.5 occurs outside the West, due to higher population density in the East. Across the US, smoke-attributable asthma morbidity predominantly occurs in spring and summer. The number of DALYs associated with smoke PM2.5 is approximately three orders of magnitude higher than DALYs associated with gas-phase smoke HAPs. Our results indicate awareness and mitigation of landscape-fire smoke exposure is important across the US. Plain Language Summary The pollutants from landscape (wild, prescribed, and agricultural) fires are expected to have an increasing impact on air quality and health in the United States (US) across the current century. The implications of landscape-fire smoke on the regional and seasonal distribution of health events and the relative health importance of specific pollutants within smoke are not well understood. In the present study, we assess the seasonal and regional distribution of the health impacts from US smoke exposure from 2006 to 2018. We also estimate the long-term health impacts for both fine particles (PM2.5) and gas-phase hazardous air pollutants (HAPs) in smoke. Although the majority of large landscape fires occur in the western US, we find the majority of deaths (74%) and asthma emergency department visits and hospital admissions (on average 75% across 2006-2018) attributable to smoke occur outside the West. Across the US, smoke-attributable asthma emergency department visits predominantly occur in spring and summer. The long-term health impacts associated with smoke PM2.5 are much higher than the estimated long-term health impacts of gas-phase smoke HAPs. Our results indicate awareness and mitigation of landscape-fire smoke exposure is important across the US, not just in regions in proximity to large wildfires.

Automated summary

As anthropogenic emissions decrease and emissions from landscape fires increase in the US over the next century, the importance of landscape-fire smoke on air quality and health will rise. The specific impacts on health events and the relative importance of pollutants within smoke are not well understood. This study assesses the distribution of health impacts from US smoke exposure from 2006 to 2018 and highlights the need for awareness and mitigation of landscape-fire smoke exposure across the country.