Microplastics of our own making are turning up in the rain, wind, soil, and snow of the most remote and mountainous regions on our planet.
"I didn't know what to expect in terms of results, but it really surprised me to find microplastics in every single snow sample I analyzed," says 'plastic detective' Imogen Napper from the University of Plymouth.
"Mount Everest is somewhere I have always considered remote and pristine. To know we are polluting near the top of the tallest mountain is a real eye-opener."
Given how far and wide microplastics have spread, both on land and in water, the discovery is not particularly surprising, although it's still shocking.
While a lot of attention has been paid to plastic pollution in the world's oceans, recent estimates have found nearly as many synthetic microfibres are amassing on land and in freshwater sources, in large part because of our clothing.
Despite Kathmandu, the nearest major city to Everest, located 160 kilometres (99 miles) away, Mount Everest isn't free of microplastics. A new analysis of the region's snow and stream water reveals the highest altitude microplastics have ever been recorded.
In each and every snow sample collected during a 2019 expedition, a significant concentration of microplastics was found in the lab – more so than other samples taken from mountainside streams, possibly because these waters were moving quickly and were regularly diluted by melt.
Everest Base Camp was particularly polluted. This is where the majority of climbers spend time, sometimes for a month or longer, and even those that are courteous of their waste are probably contributing to the problem unknowingly.
The tiny plastic pieces collected for the study were smaller than 5 millimetres and were mainly made of polyester and acrylic fibres, as well as some nylon.
These are the very polymers used to make most outdoor clothing, which needs to be waterproof and insulated, and sturdy outdoor gear, like tents, ropes, and flags.
"Subsequently," the authors write, "it is highly suspected that these [microplastics] originated from performance clothing and equipment used by climbers and trekkers rather than existing macroplastic debris."
Mount Everest is sometimes described as 'the world's highest junkyard'. For decades, a surging number of annual climbers have left behind remnants of their visit at basecamp and along the mountainside.
Last year, the Nepalese Army launched a campaign to clean up roughly 10,000 kilograms (22,046 pounds) of waste from the national park, but not all plastic is so easily collected.
Instead of coming from food and drink waste, the new study suggests most microplastics are accumulating in the region from stuff climbers take with them when they leave.
"Microplastics haven't been studied on the mountain before," says Napper, "but they're generally just as persistent and typically more difficult to remove than larger items of debris."
Prior research, for example, has found one simple coat of polyester clothing could release a billion microplastics per year. This means even the most conscientious environmental climber could be shedding plastics into the environment even as they reduce, reuse, and recycle larger items of waste.
There's also the problem of wind, which we've only just come to realise. Recent findings reveal microplastics are being carried to some of the most remote regions on Earth by strong currents of air, and this might explain some of the pollution found near base camp.
Mount Everest, after all, is a windy place, but in turn that also means any plastics deposited here are probably blown around even further.
Scientists still don't know what these tiny particles of plastic are actually doing to human health or the health of our ecosystems. While we're probably consuming over 70,000 microplastics a year at least, scientists still are not sure at what threshold this pollution becomes toxic or what the subsequent harms may be.
While the research found fewer microplastics in the water surrounding Mount Everest, it's entirely possible that even these lower concentrations could be consumed by locals who reside downstream.
As a result, the authors call for more samples and analysis so we can better understand this potentially crucial issue.
Figuring a way to clean up these tiny plastics is a whole other problem. Especially when the highest ones are 8,440 metres (27,690 feet) above sea level.
"These are the highest microplastics discovered so far," says Napper. "While it sounds exciting, it means that microplastics have been discovered from the depths of the ocean all the way to the highest mountain on Earth."
"With microplastics so ubiquitous in our environment, it's time to focus on informing appropriate environmental solutions. We need to protect and care for our planet."
The study was published in Cell Press.