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What Janice Brahney saw through her microscope shocked her. A biogeochemist at Utah State University, Brahney was trying to understand how dust, carried on the wind into wild areas of the Southwest, influenced the nutrient makeup of soil there. But when she looked at the magnified dust samples, she saw bright pink fragments of plastic. “It was kind of an accident,” she says. “I was like, ‘Oh my gosh.’ I was very surprised.” 

The discovery may have been unexpected, but it became Brahney’s focus. For the next two years, she dedicated her efforts to understanding the scale at which microplastics are invading protected natural areas in the United States. Her findings , and they are striking.

Every year, wind and rain bring around 1,000 metric tons of plastic—the equivalent of 120 to 300 million plastic bottles—to the 11 western national parks and protected areas that Brahney studied, including Grand Canyon National Park in Arizona, Craters of the Moon National Monument and Preserve in Idaho, and the High Uintas Wilderness in Utah. Most of these microplastics were tiny fibers, typical of clothing with polyester or nylon, carpets, and outdoor gear. The remaining 30 percent were microbeads, the tiny spheres made of solid polyethylene frequently used in scrubs and other beauty products. They came in all the colors of the rainbow.

“We need to recognize that this is a pollution source that isn’t going away,” Brahney says. “It’s not just ‘out of sight, out of mind.’ It’s there, and it could be causing a lot of problems.” Since plastic degrades into ever-smaller pieces over hundreds of years, scientists have suggested that microplastics circulate not only through rivers and oceans, but also through the atmosphere, transported by wind, deposited to the ground, and then picked up again to land somewhere else. Brahney’s study is one of the first to measure the specific distances and quantities of the microplastics' movement through wind.​ 

In recent years, scientists have found microplastics throughout the natural environment, from Arctic ice to the ocean floor’s deepest crevices, floating in freshwater and mixed into the sand at for migratory birds. In 2018, a global research partnership in 88 percent of the 2,677 water samples they collected in every ocean and several watersheds. “We are living in the ‘plasticene,’” or era of plastic, says Abigail Barrows, the marine research scientist who led that study but wasn’t involved in Brahney’s research. “We are interacting with plastic more intimately than most people realize.”

For the new study, published in Science, Brahney partnered with the National Atmospheric Deposition Program, which uses weather stations to collect samples of dust carried by wind and rain into national parks and wilderness areas. Whenever she collected a sample—rainwater during a storm or dust carried by the wind—she ran a weather model that told her where those samples had been before reaching the protected areas. That’s how she confirmed that cities play a huge role in spreading microplastics through the rain. When storms had passed through cities on their paths to Brahney’s study areas, they deposited as much as 14 times more microplastics in the research stations than when they didn’t pass through urban areas.

But the plastic falling with the rain was only a fraction of what arrived on the landscape, Brahney says. Her results showed that wind brought into the parks 75 percent of the nearly 15,000 pieces of microplastics she analyzed. Most of these plastic fragments were also smaller, which might have allowed them to travel longer distances than the particles in the rain. 

The new research helps scientists to better understand how far microplastics can travel, and how wind and rain deposits them in different areas, says Steve Allen, an environmental engineer at University of Strathclyde, in the U.K., who was not involved in Brahney’s study. “In terms of sampling and how much land it covers, this is really impressive,” he adds.

The effects of microplastics—especially the smaller ones—on wildlife are still widely unknown, says Allen. “The smaller particles not only leak their own chemicals when ingested by animals, but they can also carry all the chemicals that they absorbed during the journey,” he explains. “All of those chemicals leak into the body of whatever has eaten the plastic.”

While the negative impacts of microplastics on wildlife , some studies suggest that microplastics might obstruct animals’ intestinal tracts and . Last month,  that White-throated Dippers in South Wales ate about 200 pieces of microplastics each day, presumably through the worms and insects in the birds’ diet. In a , researchers found a mean of six pieces of microplastics, mostly rayon, in the intestines of nine species of raptors that arrived dead or couldn’t be saved at the in Florida. All 63 birds in the study had microplastics in their digestive systems.

Brahney says that the presence of plastics in high mountain areas may be especially dangerous. These ecosystems have simple food webs, with a small number of species tightly interconnected. If plastic consumption starts affecting one species, it could ripple through the whole system. That’s especially concerning because microplastics appeared in greater concentration at higher elevations in the study.

There’s even evidence that microplastics can fundamentally change the natural environment by altering the temperature, moisture, and nutrient composition of soil, which can affect the growth and distribution of plants and insects, and perhaps even  

“Research like this should touch people in different ways,” says Barrows, the marine researcher. “There are more petrochemicals and plastics factories being built as we speak. We need to realize that we have to live without plastics to have a healthy environment.”