Reversing Progress: Two Decades of Wildfires Erode Air Quality Advances in Western U.S.

Over the course of two decades, wildfires have had a profound impact on air quality in the western United States. This has not only escalated health risks but also undermined extensive efforts to curtail pollution, resulting in an estimated 670 additional premature deaths annually, according to a conservative estimate.

A recent study reveals that regions prone to fires and areas downwind have witnessed a surge in premature fatalities. It suffices to recall the extensive wildfires that plagued the United States and Canada last summer, spreading a haze of environmental and health consequences from coast to coast.

The Escalation of Air Pollution Due to Wildfires

A newly conducted study has meticulously documented the toll exacted by two decades of wildfires on air quality and public health across the continental United States. The research indicates that between 2000 and 2020, air quality in the western U.S. deteriorated significantly, primarily attributable to the increased frequency and intensity of wildfires. This resulted in an annual upswing of 670 premature deaths in the region during this period. Remarkably, these fires have eroded the substantial gains made by federal agencies in improving air quality, largely through reductions in automobile emissions.

Jun Wang, the lead corresponding author of the study and James E. Ashton professor and chair in the Department of Chemical and Biochemical Engineering at the University of Iowa, underscores the disheartening reality, stating, “Our air is supposed to be cleaner and cleaner due mostly to EPA regulations on emissions, but the fires have limited or erased these air-quality gains. In other words, all the efforts for the past 20 years by the EPA to make our air cleaner basically have been lost in fire-prone areas and downwind regions. We are losing ground.”

Unfolding Air Quality Deterioration and Health Hazards

The researchers meticulously calculated the concentration of black carbon, a fine-particulate air pollutant with known links to respiratory and cardiovascular diseases, across the continental U.S. on a kilometer-by-kilometer grid.

In the western U.S., the study reports a staggering 55% increase in black carbon concentrations on an annual basis, primarily driven by wildfires.

Unsurprisingly, the most severe premature mortality rates were recorded in the western U.S., where wildfires either originated or heavily impacted regions due to smoke from fires in Canada. It is important to note that the reported increase of 670 premature deaths per year is considered a conservative estimate, given that the full extent of black carbon’s impact on human health is not yet comprehensively understood.

“Wildfires have become increasingly intensive and frequent in the western U.S., resulting in a significant increase in smoke-related emissions in populated areas,” note Wang and his research team. “This has likely contributed to a decline in air quality and an increase in attributable mortality.”

Impacts on Air Quality in the Midwest and Eastern U.S.

Wildfires have also left their mark on the Midwest, with smoke transported through the atmosphere affecting air quality. While direct health impacts currently appear minimal, Wang cautions that the situation is on the brink. Should wildfires continue to intensify or become more frequent, air quality in the region could deteriorate further.

In contrast, the eastern U.S. did not experience major declines in air quality during the 2000-2020 timeframe.

Study Methodology and Significance

To derive black carbon concentrations and premature death estimates, the researchers relied on satellite data and 500 ground-based air quality monitoring stations. While surface station data can be extensive, it lacks complete spatial coverage and can be deficient in rural areas. To overcome these limitations, the researchers employed “deep learning” techniques, enabling computer systems to cluster data and make accurate predictions regarding black carbon concentrations. Premature death estimates were calculated using a formula that incorporated average lifespan, black carbon exposure, and population density.

“This is the first time to look at black carbon concentrations everywhere, and at one-kilometer resolution,” emphasizes Wang.

Jing Wei, the lead author of the study, played a pivotal role in collecting satellite data on fine particulates and analyzing their impact on public health during his time as a postdoctoral research scholar in Wang’s research group at Iowa.

Wei, now an assistant research scientist at the University of Maryland’s Earth System Science Interdisciplinary Center, emphasizes the gravity of the situation: “The increasing number and intensity of wildfires in the U.S. counteract or even overshadow the reduction in anthropogenic emissions, exacerbating air pollution and heightening the risks of both morbidity and mortality.”

This study underscores the pressing need to address the growing wildfire crisis and its far-reaching implications on air quality and public health in the western United States.

Reference: “Long-term mortality burden trends attributed to black carbon and PM2·5 from wildfire emissions across the continental USA from 2000 to 2020: a deep learning modeling study” by Jing Wei, Jun Wang, Zhanqing Li, Shobha Kondragunta, Susan Anenberg, Yi Wang, Huanxin Zhang, David Diner, Jenny Hand, Alexei Lyapustin, Ralph Kahn, Peter Colarco, Arlindo da Silva, and Charles Ichoku, 4 December 2023, The Lancet Planetary Health. DOI: 10.1016/S2542-5196(23)00235-8

Zhanqing Li, from the University of Maryland’s Earth System Science Interdisciplinary Center, who supervises Wei, is a co-corresponding author. Contributing authors include Shobha Kondragunta, from the National Oceanic and Atmospheric Administration’s STAR Center for Satellite Applications and Research; Susan Anenberg, from George Washington University; Yi Wang and Huanxin Zhang, from Iowa; David Diner, from the California Institute of Technology and NASA Jet Propulsion Lab; Jenny Hand, from Colorado State University; Alexei Lyapustin, Ralph Kahn, Peter Colarco, and Arlindo da Silva, from NASA Goddard Space Flight Center; and Charles Ichoku, from the University of Maryland-Baltimore County. The research was funded by NASA and NOAA.

Frequently Asked Questions (FAQs) about Wildfires’ Air Quality Impact

More about Wildfires’ Air Quality Impact

• The Lancet Planetary Health Study