Microplastics have been found in some of the most remote aquatic ecosystems on earth, including in the deepest parts of the ocean. Now, scientists have discovered that these tiny pieces of plastic can also be carried by the wind into secluded terrestrial regions, such as the French Pyrenees.

The research, led by scientists at the University of Strathclyde in Scotland and EcoLab, a research center in France, involved measuring the amount of plastic pollution that fell into traps 4,500 feet up a mountain in the Pyrenees over a five-month period. On average, 365 plastic particles fell on a square-meter collector every day — levels comparable to the plastic floating through the air in megacities like Paris or Dongguan, China, despite the fact that are no major cities anywhere near the study site.

The microplastic collected, which scientists estimate traveled at least 60 miles, included fibers from clothing, fragments from plastic bags, plastic film, and packaging material. The findings were published this week in the journal Nature Geoscience.

“We’d kind of expected it in a city getting blown around,” Steve Allen, a researcher at the University of Strathclyde and co-lead author of the new study, told NPR. “But way up there? The number is astounding.”

Scientists have raised concerns in recent years about the potential health impacts on humans breathing in tiny plastic particles. Microplastics have been shown to absorb toxic chemicals and carry harmful bacteria, The Guardian reported. And plastic fibers have been found in human lung tissue. The new research is the first evidence that these tiny plastic pieces can remain airborne for long stretches and over long distances.

“We …don’t know what they do to humans,” Deonie Allen, a researcher at EcoLab and the other lead co-author of the new study, told NPR. “They’re a brand new [type of] pollution, but there’s so much of it and it’s increasing so fast that it’s something we really need to start learning about.”