A government clean-up crew is struggling to clear away everything from abandoned tents to human waste after a record number of mountaineers crowded Mount Everest this climbing season.
There is so much rubbish on the world’s highest mountain, including depleted oxygen cylinders, food packaging and rope, that climbers use the refuse as a kind of signpost.
Climbers who don't use makeshift toilets now threaten drinking water for local communities.
This year’s haul from around 700 climbers, guides and porters on the mountain has been a shock to the ethnic Sherpas, who have worked on the government’s clean-up drive this spring.
Budget expedition companies can charge as little as $30,000 (£23,500) per climber, cutting costs including waste removal.
Tents are now littering South Col, or Camp 4, which, at 8,000 metres (26,240ft) is the highest campsite on Everest, just below the summit at 8,848 metres (29,029ft).
The high winds at that elevation have scattered the tents and rubbish everywhere.
Dawa Steven Sherpa led an independent clean-up last month and has been a leading figure in the campaign to clean Mount Everest for the past 12 years.
He said: “The altitude, oxygen levels, dangerously icy and slippery slopes, and bad weather of South Col make it very difficult to bring such big things as tents down.”
Exhausted climbers struggling to breathe and battling nausea leave heavy tents behind rather than attempt to carry them down.
Mr Sherpa said the logos on the ice-embedded tents that could identify the expedition companies had been deliberately ripped out so the culprits could not be identified.
“It took us an hour to dig out just one tent out of the frozen ice and bring it down,” he said.
His expeditions alone have brought down some 20,000kg (44,000lbs) of rubbish since 2008.
Mr Sherpa estimated 30 tents had been left on South Col, and as much as 5,000kg (11,000lbs) of refuse. Bringing it down is a herculean task, when any misstep at such altitudes could be fatal.
It is impossible to know exactly how much litter is spread across Everest because it only becomes visible when the snow melts.
At Camp 2, two levels higher than base camp, the campaigners believe that around 8,000kg (17,637lbs) of human excrement were left during this year’s climbing season alone.
Some climbers do not use makeshift toilets, instead digging a hole in the snow and letting the waste fall into small crevasses. However, rising temperatures have thinned the glacier, leaving fewer and smaller crevasses.
The overflowing waste then spills downhill toward base camp and even communities below the mountain.
People living at the base camp use melted snow for drinking water that climbers’ toilets threaten to contaminate.
John All, a professor of environmental science at Western Washington University who visited Everest on a research expedition, said: “During our expedition to Camp 2, eight of our ten Sherpas got stomach illness from bad water at Camp 2.”
For the Nepalese who regard the mountain as “Sagarmatha”, or Mother of the World, littering amounts to desecration.
Climber Nima Doma, who returned recently from a successful ascent, gets angry when she considers that the sacred mountain is being turned into a dump.
She said: “Everest is our god and it was very sad to see our god so dirty. How can people just toss their trash on such a sacred place?”
The waste is creating danger for future climbers and has spurred calls for action.
Ang Tshering, former president of Nepal Mountaineering Association, said: “When the snow melts, the garbage surfaces.
“And when there is high wind, tents are blown and torn and the contents are scattered all over the mountain, which makes it even more dangerous for climbers already navigating a slippery, steep slope in snow and high winds.”
Ang Dorjee, who heads the independent Everest Pollution Control Committee, has demanded that the Nepal government – whose general oversight of Everest has come under scrutiny this year as climbers died waiting in line to ascend – should institute some rules.
“The problem is there are no regulations on how to dispose of the human waste. Some climbers use biodegradable bags that have enzymes which decompose human waste, but most of them don’t,” he said.
The bags are expensive and have to be imported from the United States.
The associations say the government should mandate the use of biodegradable bags. It would spare Mr Dorjee and his team the unpleasant task of collecting the waste and carrying it down the dangerous slopes.
The government is working on a plan to scan and tag climbers’ equipment and gear.
All climbers would have to deposit $4,000 before their ascent and might not get the money back if they return without their items.