Not only did they find microplastics; the “sheer number” the team uncovered shocked Bergmann. “We did expect to find microplastics, but the numbers that we found were a big surprise,” she said. Thousands of particles of microplastic were in nearly every sample from the Arctic; a single liter of snow contained 14,000 grains of the stuff. Microplastics were even more abundant in Europe, where there were as many as 150,000 grains of microplastic per liter of snow.

To translate: If you melted down enough Arctic ice to fill a one-gallon milk jug, it might contain as many as 53,000 shreds of microplastic.

Those microplastics may have fallen as snow, but they arrived in the Arctic through the atmosphere. The study shows that microplastics, shorn from human products and carried by global trade winds, are now accumulating in some of the harshest, most remote places on Earth.

Read: A troubling discovery in the deepest ocean trenches

The study also offers some of the strongest evidence so far that microplastics—for which human health risks are still very poorly understood—might be virtually ubiquitous in the air, water, and human environment. Tiny shreds of plastic might enter your lungs when you sniff a spring breeze, the study suggests, and they might slosh around your stomach when you drink a glass of water. Yet we still have little grasp on what, if anything, microplastics do once inside the human body.

In the animal world, microplastics seem to already be causing harm. They can block the digestive tracts of fish and insects. Some chemicals present in plastic might affect animal endocrine systems. In April, a dead sperm whale with 48 pounds of plastic in its system washed ashore in Sardinia.

Microplastics may pose a particular threat to Arctic life because the Arctic serves as a meeting point for ocean currents and trade winds from across the Northern Hemisphere. A recent study found that the Arctic Ocean contains more plastic waste than any other ocean, with roughly 300 billion pieces of detritus. When Bergmann and her colleagues combed the deep-sea floor, they found roughly 6,000 pieces of microplastic per kilogram of dry sediment. “That’s a lot,” she said.

The new study makes for “interesting and terrifying stuff,” said Joe McConnell, a professor at the Desert Research Institute, in an email. He studies how Arctic snow collects other forms of air pollution, and he was not connected to the microplastic research. “The Arctic has been contaminated by mid-latitude industrial emissions for most of the past three millennia—starting as early as the Romans and likely even earlier—so I don’t find it too surprising that very small [microplastic] particles are transported to and deposited in remote regions such as the Arctic or the Alps,” he said.