After being used as a dumping site for radioactive waste for decades, Lake Karachay, located in the southern Ural mountains in western Russia, has become the most polluted spot in the world. In 1968, during drought conditions, the wind carried radioactive dust away from the lake’s dried area, irradiating half a million people.

The radiation level in the region near where radioactive effluent is discharged into the lake was 600 röntgens per hour in 1990, according to the Washington, D.C.-based Natural Resources Defense Council, more than sufficient to give a lethal dose to a human within an hour.

[en.wikipedia.org]