Dust clouds are killing people out West—and the dangers could spread

A team of scientists takes on the big threats posed by tiny particles out West.

A PAIR OF EMPTY DOCKS sit atop dried muck at an abandoned marina, glaring reminders that the largest saltwater lake in the Western Hemisphere is disappearing. Three main tributaries empty into Utah’s Great Salt Lake, but decades of their flows being diverted for agriculture, cities, and industry—along with prolonged drought—have starved the 1,700-square-mile body of its lifeblood. Last summer the inland sea made national headlines when it dropped to the lowest point ever recorded, exposing roughly 750 square miles of sediment to the same winds that carve hoodoos and sculpt arches to the south and east.

Despite much-needed rain on this early-October afternoon, only the slimmest sheen of water glistens where the lake should be—and it will disappear within days. The patches of bare earth it will leave behind can easily turn into dust that blows straight into Utah’s largest urban area, Salt Lake City, about 30 miles to the east. Making matters worse, that sediment is full of arsenic.

Kevin Perry, an atmospheric scientist at the University of Utah in Salt Lake City, has covered nearly every inch of this sandy terrain riding (sometimes pushing) a fat-tired bicycle to sample and identify the most erodible patches. Between 2016 and 2018, he pedaled 2,300 miles—dodging lightning, bullets from trigger-happy target shooters, and roaming bison on Antelope Island, a state park that juts into the southeastern corner of the lake. And he got caught in 15 or so of the increasingly frequent dust storms on the dried lake bed, or playa. “My legs were sandblasted,” he says. “Visibility reduced to feet in minutes. Sand was in my eyes.”

By documenting the amount of vegetative cover, the presence and thickness of any biological crust produced by bacteria, algae, or mosses, and the percentage of tiny dust-prone silt and clay particles, Perry determined that 9 percent of Great Salt Lake sediments readily blow away. But as much as 22 percent could—especially if human activities, such as the use of roving all-terrain vehicles or motorcycles, destroy the crust. Perry, a meteorologist by training, estimates Salt Lake City annually gets 10 to 15 notable dust events that reduce visibility to less than a mile, up from none only 15 years ago. He has to approximate because the sensors required to monitor air quality are few in number, not well placed for his purposes, and set to measure only one 24-hour period every three days, to keep costs low. Even if dust storms are happening all the time, you have only a 1-in-3 chance of being able to measure one, he says.

Perry is part of a team of six scientists aiming to track dust, both the extent to which it moves in acute storms and the incognito chronic creep of microscopic granules called particulates that can make one year dustier than the next—or alter the airborne earth’s long-term contribution to climate change. Their project, called Dust Squared, will over five years expand monitoring, assess the particles’ effect on water quality, and develop molecular “fingerprints” to better track, model, and ultimately predict their movement. Not only do they want to know where the stuff comes from, they want to understand what travels in it—and, once it settles, what impact it has on human health and ecosystem function. Efforts to quantify the amount emitted from the Great Salt Lake could better inform land and water management policies. The project is just one example of the alliances being built by US scientists to coordinate and prioritize research efforts to investigate the rising dust threat.

“There’s not a lot of work on the impacts of dust on water quality. We see it on the snowpack, but the next step is seeing where it goes, where it ends up in the watershed. It gets pretty messy.”

—Greg Carling, hydrogeologist

Dust may be one of the biggest environmental hazards routinely swept under the rug. A 2021 study led by environmental economists at Carnegie Mellon University found that a 9.7 and 12.2 percent increase in dust in the US West and Midwest, respectively, between 2016 and 2018 resulted in 9,700 additional premature deaths annually by 2018, translating to $89 billion in damages. While ongoing drought and land and water management are factors, other possible causes of the increase in airborne particulates range from greater wildfire activity to decreased enforcement of the Clean Air Act. Particulate matter 10 microns in diameter is called PM10. Anything smaller than that can damage lung tissue, cause lung cancer, and increase risk of death. Valley fever, a fungal disease that can infect the lungs once it gets kicked up by high winds, is on the rise. Dust-caused traffic fatalities garner the most attention, however. On a Sunday afternoon in late July 2021, in southwestern Utah, poor visibility led to a 22-car pileup that killed eight and sent 10 to the hospital. “It was an extremely tragic event—we had never seen that in Utah,” says Maura Hahnenberger, the Dust Squared team member who studies how meteorology shapes dust movement from the region to the Rocky Mountains.

Dry lake beds represent the West’s largest single dust source. The Great Salt Lake is just the latest so-called terminal lake—a water body that doesn’t empty into the ocean—to go parched. The most infamous is California’s Owens Lake, whose primary tributary was diverted in 1913 to supply Los Angeles with water. By 1987, when the EPA first found the lake violated National Ambient Air Quality Standards for particulate matter, it was the largest PM10 source in the nation.

[Related: Decades of US air quality improvements may be slowing

A study released by Brigham Young University in 2020 found that Utahns may be losing roughly two years each on their life expectancies due to poor air quality. Further, it costs the state about $2 billion a year in healthcare expenses, missed work time, lost tourism, and decreased growth.

Salt Lake City residents are concerned that potentially toxic desiccated sediments will worsen their already worrisome smog. The city sits in a bowl, known as the Great Basin, that stretches from California to western Utah; the lake, to the west, is its lowest point, and the Wasatch and Uinta mountain ranges that tower over the urban center form its eastern border. In the winter, the peaks cause inversions whereby warm air traps a polluted cold layer in the valley for extended periods. In the summer, warm, stagnant air causes spikes of ozone, and, increasingly, Utah gets California’s wildfire smoke. “Typically, spring and fall were when we had really good air quality,” says Perry, “but that’s when we get our big dust storms. They are closing our good air quality window—and that puts us all at risk for poor health outcomes over time.”

AT 7,800 FEET, citron-colored aspen trees encircle an 80-year-old weather station situated where the Wasatch and Uinta mountain ranges meet. Two Dust Squared team members are installing high-elevation collection devices before the first major storm of the season dumps more than a foot of snow

Jeff Munroe, a geologist at Middlebury College in Vermont and principal investigator of the project, pours black marbles into a simple, shallow plexiglass square with five separate troughs. Dust will get trapped below the spheres, while their dark surfaces will heat up and help evaporate any snow or rain that falls into the troughs. The decidedly low-tech device will sit undisturbed in the same location, accumulating particles until his team samples them in warm weather to collect the “winter” deposits and again in the fall to check the “summer” yield.

The Uintas are one of the few mountain ranges in the lower 48 with an unusual east-west orientation. As a result, Munroe says, they offer scientists a “ready-made experiment” to study how dust moves from the Great Basin to the Rocky Mountains. “It’s this nice kind of catcher’s mitt for stuff coming from the south or north,” adds colleague Greg Carling, a hydrogeologist at Brigham Young University in Provo. With some 18 such devices spread across the range, they can determine how much falls and from which direction.

Elderly scientist hauls dust-measuring instruments on fat-tire bike across the Great Salt Lake
Kevin Perry hauls a device called a PI-SWERL—a miniature wind tunnel—across the dried bed of the Great Salt Lake. Thorn Merill

Munroe is wrapping up his 25th season in the Uinta Mountains, where he first began studying how dust shapes high-elevation ecosystems, and where he deployed the first collection devices in the Wasatch in 2020. He and Carling began collaborating in 2015. In 2019, the duo published a first attempt at determining whether the playas or urban pollution is the primary dust source in the two ranges; they found that a startling 90 percent of the particles in the Wasatch came from the playas of the Great Salt Lake, roughly 75 miles east, and Sevier Lake, around 150 miles southwest. But they couldn’t distinguish between the two sources. Carling says the next step is to differentiate the playas, then consider additional sources, such as other playas, agriculture, and oil and gas development. Jumping at the opportunity to study dust “from source to sink,” Munroe and five Utah-based colleagues pulled together to form the Dust Squared crew after landing a $5 million grant from the National Science Foundation in 2020.

One of the big questions the team aims to tackle is what, if any, impact the minerals, metals, and microbes that hitchhike on dust can have on distant ecosystems. For example, Janice Brahney, a biogeochemist at Utah State University, looks at how phosphorous-laden dust alters pH and plankton growth in alpine lakes.

Carling, meanwhile, studies whether the metals carried along degrade water quality when snow flushes into mountain streams. “During snowmelt we see this increase in metal concentrations in the river,” he says. Using samples from the headwaters of the Provo River, near the weather station, Carling has detected lead, copper, beryllium, and aluminum—none of which could have come from local rock’s parent material, a simple quartzite. “Lead shouldn’t be in these samples,” he says. “It must have come from another source.” That finding turned attention to what the wind blows in. “There’s not a lot of work on the impacts of dust on water quality. We see it on the snowpack, but the next step is seeing where it goes, where it ends up in the watershed. It gets pretty messy.” To make those connections, Carling compares what’s in dust to what’s in the samples from the Provo, a source of drinking water.

Similarly, McKenzie Skiles, a snow hydrologist at the University of Utah, has been modeling dust impacts on snowmelt in the mountains to try to get a fix on how that affects the region’s water supply and quality. Eighty to 90 percent of Salt Lake City’s water comes from snow, Skiles says, “yet current snowmelt models do not account for dust impacts.” Her research suggests the airborne soil causes the white stuff to liquefy between one and three weeks sooner than it would otherwise. Instead of a steady trickle of water through spring, this earlier thaw leaves less to flow into rivers and groundwater during increasingly hot, dry summers. In the worst-case scenario, melting causes inundation that the soil—and reservoirs—can’t absorb and store. “It’s the mountains that provide all of our water,” she says.

A swirl of dust in sepia lighting next to a blowing dust across a black background

The team’s real goal, though, is to inform policies that manage the amount of dust getting into the snowpack in the first place, which is why Carling looks for chemical fingerprints to connect what lands in the peaks to dried-out lake beds. In 2020, he showed that, although it’s slight, there is enough difference in their strontium isotopes to distinguish dust from the Great Salt Lake and sediments from the all-but-disappeared Sevier Lake. “That’s one fingerprint, but it would be better to have others,” he says. Carling and colleagues are also exploring whether they can find enough unique microbial DNA to distinguish whether their samples link back to sediment, soil, or mining.

Without fingerprinting, existing monitoring methods can miss a lot. Researchers can trace a bigger dust event back to the source, but it requires luck: A satellite must be in the right place at the right time to capture definitive images. When those images don’t exist, Skiles turns to a technique called “back-trajectory modeling,” which uses meteorological data to trace a parcel of air backward over time to see where it picked up particles. Using atmospheric computer models that determine the origins of air masses, Skiles tracked dust in the Wasatch Mountains to a single event in 2017 originating from the Great Salt Lake and desert. The model showed that event contributed roughly half of the snow’s total dust deposit.

Alternatively, the Dust Squared team can try to piece together information on events using EPA sensors, but those are limited too—down to only 19 such probes in Utah, 14 of which monitor PM2.5, the size that can most easily penetrate the lungs, and five of which track PM10. Their project will add another 550 low-cost sensors, most of them in urban areas, including PurpleAir monitors used by a popular real-time air quality smartphone app, to detect particulates below PM2.5. (About 80 percent of the state’s population lives in the urban-industrial corridor known as the Wasatch Front, extending from Brigham City to Provo and including Salt Lake City.) They also plan to install a dozen in more rural areas. In recent years, the EPA has gotten rid of PM10 sensors, since PM2.5 poses the greatest public-health concerns, but PM10 remains problematic, and without the ability to monitor it, the researchers can’t maintain a long-term record. “For dust research, it’s difficult not to have,” says Hahnenberger.

AT FIRST GLANCE, Owens Lake, 200 miles north of Los Angeles, east of the Sierra Nevada, looks like a crusty, pillaged landscape. An expanse of saline crystals covers most of the area, while streaks of crimson, salt-loving bacteria thrive in briny shallow pools. For decades, the dust generated here was hazardous to the area’s 40,000 permanent residents—and millions of visitors to the area’s national parks. By 2014, a court order required implementing dust-control measures to mitigate 44.2 percent of the 110-square-mile playa, the largest such project in the nation.

The EPA’s maximum National Ambient Air Quality Standard for coarse particulate matter is 150 micrograms per cubic meter of air during a 24-hour period, and amounts above 350 cause significant harm to human health. “At Owens Lake, we have had exceedances greater than 100 times the maximum standard,” says Phillip Kiddoo, the air pollution control officer now overseeing mitigation efforts on behalf of the state’s Great Basin Unified Air Pollution Control District. “Our highest day was around 20,000 micrograms.”

It’s taken three decades of experimentation with blankets of gravel, vegetative plantings, and shallow flooding to wrangle the dust. In the 1990s and early 2000s, the six lake sites monitored had dozens of exceedances each year; in 2020, the area topped federal limits on only eight occasions. It’s a mitigation success story, albeit one with a $2.5 billion price tag, and one that without a doubt will require ongoing maintenance. “We’ve learned that working with nature is much smarter than against nature,” says Kiddoo.

A weather station in front of a Utah mountain range dotted with yellow aspen trees
Dust collection devices and weather stations dot the Wasatch and Uinta mountain ranges. Virginia Gewin

To avoid this kind of costly saga, Dust Squared’s Perry thinks it makes the most sense to keep the Great Salt Lake alive. In June 2021, during a brutal drought, water from the Bear River—the lake’s most significant source—stopped flowing into it, even as state legislators entertained proposals to divert more of its water for other purposes. Until the Great Salt Lake began to disappear, many locals considered it a nuisance. “The public thinks it’s salt water and can’t be used for anything, and that every drop of water that makes it in the lake is wasted,” says Perry.

But a 2012 state report said different. The inland sea generates $1.3 billion annually to Utah’s economy, including $1.1 billion from industry (largely mineral extraction), $136 million in recreation, and $57 million to raise brine shrimp for aquaculture feed. The state’s $1 billion ski industry also benefits from lake-effect snow. And the area is also a prominent pathway for migratory birds. One consequence of its disappearance, though, has even greater power to galvanize public attention: “The thing that unites everyone is air quality,” says Perry.

[Related: Living in the same city doesn’t mean breathing the same air]

Because of smog levels during winter inversions, the state fell out of compliance with National Ambient Air Quality Standards nearly a decade ago, forcing it to create a pollution mitigation strategy. But the plan doesn’t take into account dust coming off the Great Salt Lake. Now, with growing public outcry to save the lake, politicians have taken steps to find solutions. Utah congressional representative Blake Moore teamed up with a California congressman to introduce the Saline Lake Ecosystems in the Great Basin States Program Act in September of 2021. If passed, the legislation would direct the US Geological Survey to study how best to manage terminal water systems in the region—knowledge that could also benefit Lake Abert in Oregon and the Salton Sea and Mono Lake in California.

Perry’s previous research has shown that the most cost-effective way to prevent dust is to stop diverting freshwater, most notably to agriculture, and replenish flows into the Great Salt Lake. “Ten feet of water, and you could solve the dust problem,” he says.

The MIT Knight Science Journalism Fellowship Program funded travel for this story.

Correction February 28, 2022: An earlier version of this story mis-named Oregon’s Lake Abert as Lake Albert.

This story originally ran in the Spring 2022 Messy issue of PopSci. Read more PopSci+ stories.