Researchers analyzing snow and stream samples from the National Geographic and Rolex Perpetual Planet Everest Expedition have found evidence of microplastic pollution on Mount Everest. While the highest concentrations of microplastics were around Base Camp where hikers and trekkers spend the most time, the team also found microplastics as high up as 8,440 meters above sea level, just below the summit. The findings appear November 20 in the journal One Earth.