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National Institute of Environmental Health Sciences

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Research Explores Link Between Global Wildfires, Climate Change, and Human Health

Tara Failey

During the 2018 wildfire season, the northern hemisphere experienced wildfires on an unprecedented scale. From the Arctic to the Mediterranean to the West Coast of North America, large blazes devastated large regions, resulting in lost homes and lost lives. The wildfires are notable because they have occurred in places, like in Alaska and Scandinavia, which have not typically experienced these events.

According to numerous studies, wildfire smoke has been associated with increased mortality, cardiac events, and a range of respiratory effects, including asthma attacks.

Map of the US color coded with risk of very large fires
The map shows projected percentage increases in weeks with risk of very large fires by mid-century (2041-2070) compared to the recent past (1971-2000). The darkest shades of red indicated that up to a 6-fold increase in risk is projected for parts of the West. This area includes the Great Basin, Northern Rockies, and parts of Northern California. (Photo source: adapted from Barbero et al. 2015 by National Oceanic and Atmospheric Administration)

These fires across the globe also have something in common: they were more likely to happen, and to burn more destructively, due to climate change. According to the 2017 Climate Science Special Report, recent decades have seen a profound increase in forest fire activity around the world.

“With increasing atmospheric temperatures, it’s clear that fire risk is going up and wildfires are becoming bigger and more frequent,” says Patrick Kinney, Sc.D., an air pollution epidemiologist at Boston University School of Public Health. “Climate change has led to decreasing soil moisture. As soil gets dryer, then the trees and brush get dryer, and they’re more prone to burn when there’s a lightning strike, or a spark, or an accidental fire.”

“As wildfires increase, more people will suffer from health problems, especially among those who live near fire-prone areas, but also far downwind since smoke can travel across the country and around the world,” said Susan Anenberg, Ph.D., an expert on global air pollution at The George Washington University’s Milken Institute School of Public Health.

Understanding Health Effects

According to the U.S. Global Change Research Program’s Climate and Health Assessment, wildfire smoke can contain a mixture of carbon monoxide, ozone, toxic chemicals, and both fine and coarse particles. These pollutants present serious health risks to both those living close to the fire, as well as those thousands of miles downwind.

“Wildfires are a large source of fine particulate matter air pollution in the U.S. and in many other parts of the world,” said Anenberg. “Breathing these fine particles is associated with a wide range of health outcomes, like chronic respiratory disease, cardiovascular disease, diabetes, and even affects our cognitive abilities.”

still image of the globe with slider to see annual wildfire coverage
The National Aeronautics and Space Administration (NASA) animated fire map shows the locations of actively burning fires around the world on a monthly basis, from March 2000 through August 2018, based on observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. (Map courtesy of NASA)

Pregnant women, children, the elderly, and people already suffering from asthma are among those more sensitive to the harmful health effects of wildfire smoke exposure, according to experts. Indigenous groups and those living in poverty will also be disproportionately impacted. “The impacts of wildfires will probably be most felt on lower-income portions of the world, because they’re less health resilient in general,” said Kinney.

Kinney further emphasizes that many research gaps remain. “There haven’t been too many epidemiologic studies to quantify the health impacts of fire smoke, as distinct from other sources of air pollution,” said Kinney. “We haven’t been able to tease out whether fire particles are more or less toxic, compared to other particulate matter, and I think that will be an important area of research in the future.”

NIEHS Wildfire Resources

NIEHS provides grants and resources to advance research on the health impacts of wildfires, and tools to protect communities and workers facing exposure to wildfires.

NIEHS Grant Opportunity: Worker Trainer Program: Partnerships for Environmental Public Health:

Advancing Research on Wildfires and Health

As communities recover from recent wildfire devastation, NIEHS grantees seek to better understand the impacts of wildfires on the health of vulnerable individuals and communities exposed to such events. For example, grantee Chris Migliaccio, Ph.D., Pharm.D., a researcher at the University of Montana, studies the acute and chronic effects as well as the mental health effects of wood smoke exposure by looking at impacted communities in Seeley Lake, Montana.

In the summer of 2017, Seeley Lake had several large wildfires that lasted from the end of July through mid-September — weeks longer than usual. After the fire subsided, Migliaccio and his team collected blood samples and looked at respiratory function in 100 volunteers, who were exposed to the fire. Early data indicated that the fire harmed their lungs and immune systems. Now, the researchers are collecting data from residents of two other towns in western Montana.

“This is the first time a research team has gone into affected communities and followed a cohort as they are exposed to wildfire smoke,” said Migliaccio. “Previous studies on this topic have been retrospective, looking at past emergency room visits and doctor’s visits.” Historical trends suggest that residents in the towns being studied will be exposed to a wildfire within the near future, which will allow the team to compare participants’ physiology, epigenetic changes, and health before and after a fire.

Another NIEHS grantee, Irva Hertz-Picciotto, Ph.D., M.P.H., an environmental epidemiologist at the University of California, Davis (UC Davis) is tracking the physical and mental health of people who were exposed to a series of 250 fires during 2007 in California’s Napa and Sonoma valleys. The UC Davis team is collecting time-sensitive samples, such as blood and placenta from women who were pregnant during the fires. This information will help to determine long-term health consequences.

Migliaccio and Hertz-Picciotto are both recipients of Time-Sensitive Research Opportunities in Environmental Health Sciences. Their research will also yield important health information relevant to other regions of the world dealing with wildfires.

Future Research Aims

To understand impacts in different regions, researchers say future studies should explore how the chemical composition of wildfires vary. Migliaccio emphasizes that the fuels burning in Montana and California, such as pine needles or plastic, could differ significantly from the fuels burning in Australia, such as eucalyptus. “Each fuel has unique chemical compositions, so when burned, could impact human health in distinct ways,” says Migliaccio.

“As a next step, we want to build partnerships with researchers around the world to access wildfire fuels from different parts of the world,” said Migliaccio. “We could burn these fuels in our exposure system to analyze particles chemically, and then do some comparative animal exposures to understand the specific health effects linked to different fuels.”

Researchers also reiterated the need for improved collaboration. “We need more studies that are conducted by interdisciplinary teams of researchers, including health professionals, fire modelers, climate experts, and air pollution experts.” said Kinney. “Understanding wildfires in a changing climate is a complex problem that can only be addressed in a multi-disciplinary way.”

“Wildfires will only get worse as climate change accelerates, which it will do over the next few decades no matter what we do,” said Kinney. “For this reason, it’s critically important to advance our understanding of how wildfires impact human health.”