The Forecast in National Parks Is Cloudy With a Chance of Plastic Rain

America’s seemingly pristine western wilderness areas and national parks—iconic landscapes including the Grand Canyon and the Rocky Mountains—are being blanketed by tiny pieces of plastic raining from the skies, according to new research. The petrochemical deluge, made up of airborne microplastics smaller than sesame seeds, deposits more than 1,000 metric tons on these western protected lands every year, the researchers estimate.“There’s no nook or cranny on the surface of the earth that won’t have microplastics,” Janice Brahney, an environmental scientist at Utah State University and lead author of the new study, tells John Schwartz of the New York Times. “It’s really unnerving to think about it.”

The new paper, published last week in the journal Science, estimates that the microplastics raining down onto the national parks and wilderness areas of the American West each year would be enough to make between roughly 120 million and 300 million plastic bottles.

The 11 national parks and wilderness areas surveyed in the new study join the ranks of other remote and inaccessible locales to have been despoiled by plastic, including Antarctica, the Mariana Trench and the French Pyrenees.

Microplastics, which are defined as pieces less than 0.19 inches long, typically come from the breakdown of larger plastics. These tiny fragments can find their way into dirt, water or be swept up by air currents and carried far from their point of origin, reports Valerie Yurk for the Guardian.

“Plastics could be deposited, readmitted to the atmosphere, transported for some time, deposited and maybe picked up again,” Brahney tells the Guardian. “And who knows how many times and who knows how far they’ve traveled?”

In a testament to the ubiquity of plastics, Brahney didn’t even set out to catalogue the long-lived pollutant’s invasion of the West, reports Erik Stokstad for Science. The study was supposed to examine how dust-laden winds supply nutrients to remote ecosystems, but after 14 months the 11 remote weather stations where Brahney was collecting dust also wound up collecting thousands of multicolored pieces of microplastic, per Science.

The study estimates that 132 pieces of microplastic fall on every square meter (roughly 10 square feet) of protected wilderness every day, the researchers write. It was when Brahney and her colleagues extended that tally to the total area of the 11 wilderness areas surveyed in the study that they reached the astronomical figure of 1,000 metric tons of plastic rain per year.

“We just did that for the area of protected areas in the West, which is only 6 percent of the total US area,” Brahney tells Matt Simon of Wired. “The number was just so large, it’s shocking.”

Unlike prior studies on airborne plastic pollution, the new work can speak to the question of where the plastic came from in the first place. Larger pieces of microplastics mostly fell during wet weather and came predominantly from neighboring urban areas, according to the Guardian. But 75 percent of the microplastics collected by the study were fine, dust-like particles that fell during dry weather and likely travelled extremely long distances to reach the collection site, according to Science.

The growing pileup of plastic in apparently pristine nature could disrupt ecosystems and that though the health risks to humans aren’t well understood, the presence of these tiny microplastics in the air, Brahney tells the Times, suggests “we’re breathing it, too.”

Humanity has produced an estimated 8.3 billion metric tons of plastic to date, and global plastic waste is predicted to increase from 260 million tons per year to 460 million tons by 2030. What the precise consequences of a world awash in plastic will be for the environment and human health remain mysterious, but the sheer scope of the phenomenon suggests they will be all but inevitable.