The Hidden Toll of Wildfires

“This is interesting. Not too thick,” said Jim Crawford, an atmospheric chemist wearing a motion-sickness patch behind his ear. It was afternoon in late July 2019, and Crawford was bearing down on a skein of wildfire smoke visible from the cockpit of a former commercial jet that NASA had retrofitted into an airborne laboratory. In the cabin, 35 scientists and engineers were calibrating their instruments. The mood was wired: Would their tools, most designed to measure urban pollutants, work in air thick with particulates? How would the 50-year-old plane respond in a smoke column? The DC-8 shuddered and jumped as it entered a plume lofted 12,000 feet high by a fire outside of Missoula, Mont. “Forty-five seconds, then turn it around,” Crawford directed the pilots. The turbulence was surprisingly mild, and he wanted to go back through it.

This was only the third flight in the aerial segment of FIREX-AQ, an ambitious three-year project led by the National Oceanic and Atmospheric Administration and NASA. It is attempting to sniff out the precise chemical composition of smoke emitted from biomass burns and determine, among other things, when, and why, it is most dangerous for human health. For six weeks last summer the DC-8 and a pair of Twin Otters similarly quilled with atmospheric-sampling instruments flew through more than 100 different columns. They ranged from a bubble of smoke rising off a tiny agricultural burn in Kansas to a mushroom cloud that shot up 31,000 feet from the Williams Flats Fire in Washington State, a burn one scientist compared to a volcanic eruption. Never before has biomass smoke been studied in such detail and range. Although fires contribute up to a third of all particles in the atmosphere, “there are very few studies that examine the specific role of the different components of smoke on disease and the severity of the disease when people are exposed,” said a director at the Environmental Protection Agency in 2018.

We know that chronic exposure to fine particulate matter, which is in all smoke, can lead to heart and lung disease, irregular heartbeats and aggravated asthma, among other issues. It was estimated to cause 4.2 million premature deaths worldwide in 2016. Likewise, long-term exposure to ozone, a gas that can form via chemical reactions when smoke enters the atmosphere, is blamed for at least one million premature deaths a year. What we lack is a fundamental understanding of how and when these toxic components and others form in different types of biomass smoke. Currently air-quality regulators treat emissions from all biomass burns as the same, even though that is not the case. By learning about these processes, the FIREX-AQ team hopes to improve the accuracy of wildfire-emissions forecasts, so that coaches know better when to cancel soccer practice, hospitals can anticipate an influx of immunocompromised people and regulators can protect outdoor workers from dangerous exposure. Their data could also help land managers light controlled burns, which mitigate the severity and health impacts of future wildfires.

Crawford checked his tablet, scrolling through real-time updates of the hundreds of particles and gases being sampled. The last time he had flown in the DC-8 was to study urban pollutants in Seoul, South Korea. Even in small cities, he said, researchers see pollution that is much worse than what he and his team were witnessing that day. “But how do all these fires add up?” he asked. “How much ozone do fires produce? What’s the chemistry for how it forms? And how do you regulate a natural phenomenon?” Carsten Warneke, a fellow principal investigator of FIREX-AQ, who is based out of NOAA’S Earth Systems Research Laboratory in Boulder, Colo., explains that air-quality models treat wildfire smoke as a smog event when it is a completely different problem.

Some 350 miles to the south, on the Gowen Field Air National Guard Base in Boise, Idaho, Warneke and 50 more scientists were sifting through meteorological patterns, fuels, real-time satellite data and ongoing fire updates to determine which of the West’s wildfires met the most criteria for FIREX-AQ’s goals. “There are a lot of scientists, and they all want slightly different things,” said Amber Soja, an associate research fellow at the National Institute of Aerospace, who was responsible for briefing the 400 researchers involved in FIREX-AQ on that day’s fire activity.

For today’s mission, the team had picked the North Hills Fire in Montana as the DC-8 taxied onto the runway for takeoff. It had the most pronounced smoke column of the nine fires being considered. At a relatively small 4,600 acres, the blaze was wholly unremarkable—and that is what made it scientifically alluring. Although U.S. Forest Service firefighters were still working to control the flames, they granted the DC-8 permission to sample the plume at different points in time and space, thereby capturing what was in the smoke and how it changed as it moved downwind, interacting with new conditions and environments.

After passing through the plume for the 16th time in an hour, Crawford received a message from Warneke at mission command. It contained a satellite image of a smoke column shooting above the clouds just below California’s Mount Shasta, almost 800 miles to the southwest. Warneke had drawn a circle around the plume and scrawled next to it in red ink, “GO HERE NOW!”

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