Microplastics in Death Zone

Scientists have identified the highest recorded microplastics ever found on Earth - at an altitude of more than 8,000 metres, close to the summit of Mount Everest.

Samples collected on the mountain and in the valley below it revealed substantial quantities of polyester, acrylic, nylon, and polypropylene fibres.

The materials are increasingly being used to make the high performance outdoor clothing commonly used by climbers, as well as the tents and climbing ropes used in attempts to climb the mountain.

As a result, researchers have suggested the fibres - the highest of which were found in samples from the Balcony of Mount Everest, 8,440 metres above sea level - could have fragmented from larger items during expeditions to reach the summit.

However, they have also surmised the plastics could have been transported from lower altitudes by the extreme winds which regularly impact the mountain's higher slopes.

The research, published in One Earth, was led by researchers from the University of Plymouth's International Marine Litter Research Unit, working with colleagues from the UK, USA and Nepal. It was supported by the National Geographic Society and Rolex.

The samples were collected in April and May 2019, as part of National Geographic and Rolex's Perpetual Planet Everest Expedition, and then analysed in specialist facilities in Plymouth.

Of 19 high elevation samples collected from the Mount Everest region for microplastic analysis, 11 were snow and eight stream water.

This included streams along the trekking routes close to the Khumbu Glacier, in the snow at Everest Base Camp, and high into the Death Zone near the mountain's summit.

The highest quantities (79 microplastic fibres per litre of snow) were found at Base Camp, where summit expeditions are based for periods of up to 40 days. However, evidence was also found at Camps 1 and 2 on the climbing route, with 12 microplastic fibres per litre of snow recorded from the Balcony.

There were lower quantities in streams leading down from the mountain to the Sagarmatha National Park, with scientists saying this could be due to the continuous flow of water created by the region's glaciers.

The first confirmed summiting of Mount Everest in 1953 coincided with the global rise to prominence of plastics and their use in society.

From a time in the 1950s when it had very few visitors, the Sagarmatha National Park (which includes the mountain) welcomed more than 45,000 visitors in 2016, while in 2019, climbing permits for Everest were issued in Nepal.

Over the same period, the versatility of plastic materials has resulted in a substantial increase in their use from five million tonnes globally in the 1950s to over 330 million tonnes in 2020.

• The full study - Napper et al: Reaching new heights in plastic pollution - preliminary findings of microplastics on Mount Everest - is published in One Earth, doi: 10.1016/j.oneear.2020.10.020.

• The National Geographic and Rolex Perpetual Planet Everest Expedition is the most comprehensive scientific assessment of Mount Everest in history. The expedition team studied five areas of science that are critical to understanding environmental changes and their impacts: biology, geology, glaciology, mapping, and meteorology.