From an elevation of 27,600 feet, just below the summit of Everest, researcher Mariusz Potocki could see one of the planet’s most dramatic scenes – the snow-capped Himalayas against a deep blue sky. He was on a mission to gather snow and ice samples at the summit, but just above him was another startling sight: a line of climbers so dense that a photo of it went viral.

His team had stopped at a resting spot climbers call “The Balcony,” and the snow there was littered with feces, oxygen bottles and other trash. But he wanted to gather what samples he could, so he ascended a short distance to find some cleaner snow off to the side of the trail. “I just pulled out the bottles and took samples,” he said.

And then another surprise: There, at the roof of the world, the snow samples showed traces of toxic chemicals known as PFAS, laboratory analyses done later showed. More notable results came from samples his colleagues gathered at lower elevation, which revealed these substances at levels far higher than at other mountains around the world.

“We were shocked,” said Kimberley Miner, an assistant research professor at the University of Maine Climate Change Institute, who coordinated the research remotely from the United States. “We retested everything like three times, because it was much higher than we expected.”

The study by Miner and colleagues, published in December, was part of the 2019 National Geographic and Rolex Perpetual Planet Everest Expedition, a large, interdisciplinary research project intended to understand the climate change threats facing mountain systems. It shows chemical fingerprints smudging even the world’s tallest peak in ways unseen and previously unstudied.

“The purpose of the expedition was to see if the highest parts of the planet are affected by human activity,” said Paul Mayewski, the expedition leader and director of the university’s Climate Change Institute.


Miner’s research has taken her all over the world to study chemicals in glaciers, especially persistent organic pollutants such as PFAS – shorthand for per- and polyfluorinated substances. Sometimes called “forever chemicals,” these are toxic compounds that break down slowly and accumulate over time in people and other animals.

Such pollutants are found in low concentrations in the atmosphere, and they are blown all over the globe. Then, when it rains or snows, they often are deposited on the ground. So Miner suspected the Everest samples would only show low levels of persistent chemicals from this sort of atmospheric deposition.

But when the Everest samples were shipped to an analytical lab, she learned about the PFAS levels that were particularly high in the samples from lower down on the mountain.

“I thought we’d screwed up, and we hadn’t,” Miner said. “We got consistently these very, very high levels.”

Miner’s samples showed two specific PFAS chemicals were especially high – perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). The chemicals have been used since the 1950s to repel stains and water in carpeting, upholstery and apparel; in nonstick cookware and food packaging; and in floor wax, textiles, fire fighting foam and sealants. Neither is still manufactured in the United States, but they are made in other countries.

Both have been linked to health problems. According to the Environmental Protection Agency, “both chemicals are very persistent in the environment and in the human body – meaning they don’t break down and they can accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects.”


These effects may include increased cholesterol, changes in liver enzymes and increased risk of kidney or testicular cancer, according to the Centers for Disease Control and Prevention.

“What we found was that the PFOS was at such higher levels than had been reported anywhere else in high mountain ranges,” Miner said. “And then the rest of the story was how the heck did these get there, and why were they so high?”

Fortunately, Cyclone Fani dropped 10 inches of fresh snow while the expedition was still at the Everest Base Camp, where a colleague of Miner’s at the Climate Change Institute, Heather Clifford, was gathering samples for the team. (The Base Camp is at an elevation of about 17,400 feet and more than 1,000 people were there at the time.)

Clifford took samples of the fresh snow, and one of the samples showed no PFAS; the other a trace. Taken together, the findings suggest that the high levels of PFAS were not from atmospheric deposition. Instead, it appeared that they had been shed from climbers’ outdoor gear such as parkas and tents, which are often treated with chemicals to weatherproof.

Other samples, gathered for a different research group, found microplastics – shreds of polyester – that probably came from outdoor gear. The plastic levels were highest in the areas most used by climbing teams, as with PFAS.

“You’re seeing the highest concentrations where you have the most people and the most garbage,” Miner said. “It’s kind of like sampling a frozen landfill.”


Fabric companies have long used PFAS to repel water in outerwear, although some companies have now moved away from the chemicals for environmental reasons. W.L. Gore & Associates, the maker of Gore-Tex, for instance, said the company does use some chemicals in the PFAS family, but has transitioned to those believed to be less harmful, Gore spokesperson Amy Calhoun said. Of the four compounds Miner detected on Everest, Calhoun said, three “have either been eliminated from or never used in Gore’s consumer fabrics supply chain.” But traces of the fourth one may still be detected in some of its products.

Rainer Lohmann leads a University of Rhode Island research center focused on PFAS. He said he accepts that the chemicals Miner found probably came from outdoor gear, but said he would like to see more sampling on Everest to fill out the picture.

Lohmann said the levels of PFAS in Everest meltwater, although higher than expected from an alpine glacier, would still be within safe drinking water limits in the United States.

Still, Miner said she is concerned about possible health risks as more chemicals melt out of glaciers.

“The more chemicals and the more plastics we put into the environment, the more they are going to build up and they are going to stay, and they are not going to go away,” Miner said. “And it is going to impact us more and more, in lots of different interlocking ways.”

Lohmann said it is especially striking to see this pollution on Everest.

“Everest is treasured very highly as a unique monument for the globe,” he said. “It’s kind of sad to see very high concentrations at some places on the mountain. We say, ‘Take nothing but pictures, leave nothing but footprints,’ but we leave chemicals.”

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