Artificial lakes containing 50 years of radioactive waste could leak into the rivers of the Ural Mountains within a few years, according to a letter sent by the governor of Russia’s Chelyabinsk region to Russia’s prime minister last month. The area near the Mayak nuclear reprocessing plant is known as one of the most radioactive places on the planet. Chelyabinsk’s vice governor, Gennady Podtyosov, said on Friday that contaminated water might burst the lakes’ dam in three to four years, sending waste flowing into the Arctic Ocean.