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Carried by wind and rain, plastics pollution is contaminating Rocky Mountain National Park and other western wildernesses

Scientists tracking the spread and fallout of inhalable fragments measured heaviest depositions at high-elevation Colorado sites

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New research finds plastics pollution is spiraling, spreading thousands of miles in wind as well as through rainwater, with the heaviest deposits of inhalable particles measured at high-elevation Colorado sites such as Rocky Mountain National Park.

This peer-reviewed research led by former University of Colorado scientist Janice Brahney, now at Utah State University, concluded that more than 1,000 tons of plastics fragments a year contaminate 11 celebrated public land conservation sites in the western United States. These also included the Grand Canyon in Arizona, Joshua Tree National Park in California, Craters of the Moon in Idaho, the Wind River Mountains in Wyoming and Bryce Canyon National Park in Utah.

An image of plastics particles, microbes ...
An image of plastics particles, microbes and fibers found in wet and dry deposition samples from National Park and Wilderness areas of the western United States.

Roughly 4% of the particles in dust collected at the sites during winter proved to be plastics fragments, the researchers found in a peer-reviewed study to be published in the journal Science on Friday — raising questions about human health and ecosystem harm as scientists project a worldwide environmental plastics accumulation of 11 billion tons by 2025.

“Plastics don’t decompose. They just break down into smaller and smaller fibers, and that allows them to be transported through the atmosphere, repeatedly being carried through the atmosphere,” Brahney said in an interview.

“The fibers are within the size range where they can be inhaled and lodged in lung tissue. There’s some concern about human health,” she said. “We cannot really escape the pollution that we’ve allowed to happen. And there are still a lot of open questions about the implications for ecosystems.”

The researchers backed by National Science Foundation and state funding gathered 340 dust and rainwater samples over 14 months in 11 national parks and wilderness areas and found 98% contained tiny brightly colored plastics fragments. They analyzed these using microscopes. They found the highest daily average deposition, 435 plastic particles per square meter, in Rocky Mountain National Park, compared with 140 near the Rocky Mountain Biological Lab in Gothic, 148 near Indian Peaks west of Boulder, and 112 on the south rim of the Grand Canyon.

This study stands out as the latest in a growing body of research on how plastics widely have contaminated the planet, a worsening global problem. Congress has balked at addressing it. While state and local governments increasingly have restricted consumer one-time use of plastics such as shopping bags, national legislation introduced Feb. 11 by Sen. Tom Udall, D-NM, and Rep. Alan Lowenthal, D-Calif., to hold plastics producers financially responsible was referred to a subcommittee and is expected to die.

Last fall, U.S. Geological Survey scientists completed separate research on rainwater around metro Denver and in Front Range mountains that detected microscopic bits of plastic in more than 90% of their samples. These federal scientists found the most plastic particles in water samples drawn from the urban sites along a line from the National Jewish Health hospital in east Denver through downtown to Arvada, the Rocky Flats National Wildlife Refuge, CU Boulder and Boulder Canyon. They also found plastics contaminating rainwater at mountain sites near Nederland and Loch Vale at an elevation of 10,364 feet in Rocky Mountain National Park.

Plastics industry production for packaging, construction and other uses tops 348 million tons a year worldwide. The average American generates 340 grams of plastics waste each day, the amount in 40 disposable water bottles, according to a 2017 study in Science Advances. The same resilience and durability that make plastic convenient also means plastics waste stays around.

Human health scientists years ago established that chemicals in plastics can affect animal endocrine and lymphatic systems that regulate hormones and toxins. However, the human health and environmental impacts of plastics pollution remains largely unexplored.

“We can definitely anticipate human health and ecosystem consequences, but we don’t know to what degree,” Brahney said.

The researchers analyzed types of plastic fragments and pinpointed initial sources in cities. They were trying to determine how these spread in water and eventually, when they become smaller, across large distances in air.

They focused on fragments measuring between 10 microns and 4 microns (the width of a human hair is 70 microns) that easily become airborne, leading to a continuous re-circulation — spiraling — in the natural environment.

Airborne pollution “accounted for more than 75% of the plastic mass deposited,” the final report reads. “This result, along with the relationship of dry deposition to large scale climate patterns, suggests that while urban centers may be the initial source, plastics accumulate in the atmosphere over longer time periods, are transported long distances and are deposited during favorable conditions such as slower air-mass velocities or intersections with mountain ranges.”

The higher the elevation, the scientists found, the higher the deposition rates in wilderness and parks.

For collecting dust, they put 10 inch-diameter glass plates in buckets. They removed leaves from samples and installed blocks to prevent wind from re-churning dust. They also collected rainwater in buckets.

Most of the fragments came from garments (fleece, polyester, nylon) and industrial materials. Some came from paints and coatings. Depositions in remote areas were concentrated in line with prevailing wind patterns.

The scientists had hypothesized that they’d find less than 1% of dust particles were plastics, Brahney said. Instead, they found plastics represented from 2% to 6% of particles in their samples. And, in exploring the heaviest depositions at high elevations, they considered whether the proximity of Rocky Mountain National Park within 50 miles of urban Denver and Fort Collins might be a factor as more people leave cities seeking a connection with nature, entering with polyester and nylon clothing, tents, climbing ropes and other plastic material. But they measured the most plastics during winter months when park visitation is lowest.

They concluded that tiny fragments spread increasingly through wind over large distances, spanning continents, with plastics pollution likely wafting into Colorado from as far as China.


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