The problem is rampant: tiny pieces of plastic littering the world.
They float in giant patches in the Pacific. They wash down rivers and creeks. They seep into the soil of hills and valleys.
And now, a growing body of research says they’re falling from the sky.
One of the latest studies, which examined microplastics in national parks across the West, suggests that these mostly invisible particles are drifting high in the atmosphere and dropping out with wind and rain, sometimes thousands of miles from their source. An average of more than 100 bits of plastic is likely accumulating across every square meter of the country each day, according to the researchers.
The new study comes as government regulators struggle to get a handle on the dispersal of plastic waste. The use of plastic has grown immensely in recent decades because of its durability and malleability, the same qualities that make it pervasive as a pollutant. Fragments of plastic now collect in the environment from any number of products, including broken-down bottles and packaging; paints and sealants; and fibers from clothing, furniture, and tires.
Last week, California’s Water Resources Control Board became the nation’s first government agency to define microplastics for water regulation, a step toward monitoring the contaminant in the state’s rivers, lakes, and bays.
“California has been pushing the envelope on this issue,” said Mark Murray, executive director of Californians Against Waste, a group that advocates for curbing the use of plastic and helped enact the state’s first-in-the-nation ban on single-use plastic bags. “But our policymaking has not been quick enough to get in front of plastic pollution because we keep discovering new ways that it’s getting into the environment.”
The study published this month in the journal Science is the most definitive yet to show the atmospheric delivery of microplastics.
The paper’s lead author, Janice Brahney, an assistant professor of watershed sciences at Utah State University, was actually studying airborne dust in the western United States when her microscopic samples kept getting clouded by colorful pieces of plastic.
“I was just completely taken aback that this was a phenomenon that was happening,” she said.
Wanting to understand more, Brahney began recording the amount of plastic in her dust collections at 11 national parks and wilderness areas, which included Joshua Tree, Canyonlands, and the Grand Canyon.
She found that more than 1,000 tons of microplastic was being deposited across these remote areas in a year’s time, the equivalent of between 123 and 300 million ground-up plastic water bottles. It’s about 132 pieces of plastic per square meter on average — amassing daily.
Nothing could account for so much plastic at the sites, considered among America’s greatest natural treasures and largely pristine. So Brahney convened with others who have expertise on the material and meteorology to figure how the compound got to these places.
The research team concluded that larger shreds of plastic, just slightly smaller than a grain of rice, had been swept up in nearby cities by storms and dropped with rain or snow. Smaller shreds, undetectable to the naked eye and more prevalent, had circulated in atmospheric channels, like the jet stream, and found their way across oceans before descending. The team analyzed weather patterns to deduce the movement of the microplastics.
The most debris was found at Rocky Mountain National Park, likely because of its proximity to Denver. Accumulation there averaged more than 400 pieces of plastic per square meter each day.
Prior studies had documented microplastics in such far-flung spots as the French Pyrenees and the Arctic. None, however, had examined their migrations in such detail.
While the exact sources of the plastic weren’t traced in Brahney’s study, the researchers say most of it came from clothing and industrial materials and the rest came from primarily larger, broken-up products.
Extrapolating from Brahney’s 11 test sites, she calculated that more than 22,000 tons of microplastics likely fall across the contiguous United States annually.
“This really points to how pervasive plastics are and that there’s just nowhere on the planet we won’t find them anymore,” she said.
Murray, with Californians Against Waste, had hoped to take a small bite out of the problem with a statewide ballot measure this November. The initiative sought to require manufacturers of single-use plastic products to make their goods more biodegradable and pay fees to fund their disposal. It would have also funded cleanup of places polluted by plastics.
The measure failed to get enough signatures to qualify for the ballot after signature-gatherers stopped work during the coronavirus pandemic.
Environmentalists now are pinning their hopes on two bills in the state Legislature, SB54 and AB1080. Both would similarly phase out the production of single-use plastic packaging and products in California.
Microplastics in parks
A new study found a surprising number of small plastic particles being deposited from the atmosphere at several wilderness sites. Following are the average number of plastic pieces that accumulated per square meter per day.
Grand Canyon National Park (Arizona): 112 pieces
Joshua Tree National Park (California): 54 pieces
Indian Peaks Wilderness (Colorado): 148 pieces
Rocky Mountain National Park (Colorado): 435 pieces
East River special focus area (Colorado): 140 pieces
Craters of the Moon National Monument (Idaho): 139 pieces
Great Basin National Park (Nevada): 107 pieces
Bryce Canyon National Park (Utah): 80 pieces
Canyonlands National Park (Utah): 48 pieces
High Unitas Wilderness (Utah): 120 pieces
Wind River wilderness (Wyoming): 68 pieces
Source: “Plastic Rain in Protected Areas of the United States,” Science magazine
“In January, we thought this legislation was going to be a slam dunk, but the world has changed,” Murray said. “I think this study (in the journal Science) will help us make the case that we can’t wait on it.”
More than 350 million tons of plastic is now produced annually across the globe, nearly half of which goes to single-use products. Production is expected to increase as the relatively inexpensive, lightweight material is used in more and more goods, including modern necessities like cell phones, medical equipment, and sportswear. Most plastic is made from crude oil.
Last week, the State Water Board began the process of monitoring and perhaps eventually regulating microplastics in drinking water. The agency approved a legal definition of the material, detailing its size and composition, so the compound can be consistently tracked.
While plastics are widely known to injure and even kill wildlife, perhaps most notably birds and marine life, the impact of the material on the broader environment and in humans who ingest it is less studied.
“We know enough to know it doesn’t belong out there,” said Scott Coffin, research scientist with the State Water Board, who is helping launch the agency’s oversight of microplastics. “If there is a health concern through drinking water or inhalation, we’ll definitely take these control measures a lot more seriously.”
The State Water Board is scheduled to introduce its water testing program next year.
“We’re not trying to scare people,” said Darrin Polhemus, a deputy director at the agency. “We’re not sure what the health consequences are, but we want to begin having that conversation.”
Kurtis Alexander is a San Francisco Chronicle staff writer. Email: kalexander@sfchronicle.com Twitter: @kurtisalexander
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