From the frozen wastes of Antarctica to the heights of Mount Everest, microplastics have been found in some of the most remote places on Earth. And their range continues to expand.
Recent research published in iscience Researchers have found that one of Nepal’s highest snow-filled lakes, located at an altitude of 4,917 meters (16,132 feet) in the Himalayas, contains high amounts of microplastic pollution. Researchers detected an average of 42 microplastic particles per liter of water, highlighting the reach of microscopic plastic pollution in some of the world’s most remote environments.
“This is yet another evidence that the high consumption of plastics in countries of the Global South is coming back to harm us. We are essentially getting an ax in our own feet.”
“This is yet another evidence that heavy plastic consumption is coming back in countries of the Global South and is harming us,” said Tista Prasai Joshi, a water scientist at the Nepal Academy of Science and Technology in Kathmandu. “We’re basically hitting the ax with our own feet.” Joshi, who was not involved in the new study, added that plastic use is so woven into daily life that many people are unaware of its impact on the ecosystem. Increasing numbers of tourists in countries like Nepal are only accelerating the spread, and microplastic pollution is spreading to remote areas of the Himalayas.
In 2019, Imogen Knapper, a marine scientist at the University of Plymouth, and her colleagues reported the presence of large amounts of microplastics in snow and river water around the Everest Base Camp region, about 5,300 meters (17,388 feet) above sea level. The discovery made headlines around the world.
Despite the widespread recognition of the Everest Base Camp study, few studies have investigated microplastic pollution in high-altitude lakes. Studies like this are especially important because these lakes hold water much longer than rivers, making them valuable archives of pollution and preserving evidence of pollution for years or even decades.
Journey to Tilicho
To address this gap in research, Sahil Shrestha, an environmental researcher at Tribhuvan University’s Phulchowk Campus Institute of Engineering, and his colleagues turned a multi-day Himalayan trek into a field expedition. Shrestha selected six locations on the accessible coastline around Tilicho Lake for sampling. At each location, they submerged a stainless steel bottle about 20 centimeters below the water surface with their bare hands to prevent microplastic contamination from gloves, opened the cap, filled the bottle with water, resealed it, and took the sample home for analysis.
Shrestha was particularly concerned about environmental contamination because it takes time to transport samples from a remote lake to a laboratory in Kathmandu, and contamination can occur along the way. Considering the possible contamination scenarios, he introduced several control measures.
“This is why we continued to fly,” he said. “Basically, I carried distilled water with me the entire trip in a steel bottle that I rinsed clean.”
Knowing that the water was uncontaminated at the start of the trip allowed Shrestha to re-measure the water upon returning to the lab to see if it had become contaminated during the trip (for example, by carrying it in a backpack). If the trip blank shows signs of contamination, scientists can assume that the collected sample is contaminated as well and subtract the known contamination level from the analysis. Trip blanks and field blanks are standard quality assurance techniques used in environmental chemistry research.
Shrestha also carried field blanks to keep in mind the possibility of microplastics in the air. At the scene, he poured distilled water from the lab into another bottle. The idea was to account for the possibility of airborne microplastics and subtract it later to calculate the net microplastics in the water only.
The sampling experience left a strong impression on Shrestha. One reason for this was that he and his colleagues had to carry up to 15 liters of water between sampling sites. “For both of us, transporting liters of water to each site was a challenging but fun part of the process,” he said.
plastic is plentiful
Polyester, polyethylene, and polypropylene are commonly used in hiking equipment, jackets, tents, plastic bottles, bags, etc., and all of these can release microplastics while visitors explore the area.
Once in the lab, Shrestha’s team performed further analysis, including removing organic matter, filtration, and microscopy to classify the types of microplastics. They found that microplastic pollution was higher in areas of the lake that were more accessible to tourists. The main types detected were polyester, polyethylene, and polypropylene. These materials are commonly used in hiking equipment, jackets, tents, plastic bottles and bags, all of which can release microplastics while visitors explore the area, suggesting that tourism is the most likely source of pollution.
Shrestha pointed out that while there is still no evidence that Lake Tilicho flows into rivers, many lakes in the Himalayas flow into rivers and feed downstream communities. The findings suggest that microplastic contamination of water sources has far-reaching ramifications for human health and downstream ecosystems.
Mr. Shrestha emphasized that such research is needed to inform policy and regulatory decisions.
“Tilicho Lake is located in the Annapurna Conservation Area Project (ACAP) area and these conservation programs should restrict trekkers from carrying plastic bottles and polythene bags,” he said. “Overall, the trekking equipment industry contributes significantly to microplastic pollution in remote areas, and this should be addressed through international cooperation.”
—Saugat Borake, science writer
