Too much poo and wee is being left behind by climbers on Mount Everest.
The issue is causing pollution and could spread disease, says the boss of Nepal’s mountaineering association.
Ang Tshering wants Nepal’s government to get visitors to dispose of their waste properly.
He says faeces and urine have been “piling up” for years around the four camps. “Climbers usually dig holes in the snow for their toilet use and leave the human waste there.”
More than 700 climbers and guides spend almost two months on the mountain slopes each season, which began this week and ends in May.
“It is a health hazard and the issue needs to be addressed,” says Dawa Steven Sherpa, who has been working on clean-up expeditions since 2008.
Some climbers do carry disposable travel toilet bags to use in the higher camps, he explains.
At base camp there are toilet tents, which have drums into which human waste goes. These can be properly disposed of after they are carried to a lower area.
The camps between the base and the summit do have tents and other supplies, but no toilets.
The government in Nepal has yet to come up with a solution to the problem of human waste disposal – but officials will be monitoring the rubbish on the mountain, says the head of the government’s mountaineering department Puspa Raj Katuwa
New rules mean each climber must bring 8kg (18lb) of rubbish when they return to base camp.
That is the amount experts believe a climber discards along the route.
Teams also make a $4,000 (£2,600) deposit, which they lose if they don’t stick to the rules.
Last year’s season was cancelled after 16 local guides were killed in an avalanche in April.
In total, hundreds of people have died trying to scale Mount Everest, which was first conquered by New Zealand climber Edmund Hillary and his Sherpa guide, Tenzing Norgay in 1953.