A new study discovered the extent of pollution on Mount Everest soil, found to contain dangerous levels of arsenic and cadmium.
Both heavy metals were found at levels higher than those the US Environmental Protection Agency considers acceptable, says Samantha Langley-Turnbaugh of the University of Southern Maine in Gorham.
Langley-Turnbaugh's student Bill Yeo collected soil and snow samples every 300 metres between 5334 and 7772 metres up, reports New Scientist.
All the snow samples had high levels of arsenic and cadmium, and all the soil samples had high levels of arsenic.
Mountaineers rely on melted snow for drinking water, so the toxic metals "could be a concern", says Langley-Turnbaugh. High winds blow the contaminated soil around as dust, so breathing it in could also pose a risk.
"People at Everest base camp often wear ventilators, simply because there is so much dust," Langley-Turnbaugh said.
Air pollution from Asian industry is probably to blame. Concentrations of both arsenic and cadmium were higher in the soil further up the mountain, as would be expected if high-altitude winds were depositing them.
Langley-Turnbaugh says there is very little information available about pollution on high mountains like Everest - because to get samples you have to climb them.
The study appears in Soil Survey Horizons.