Karabash is a town in Chelyabinsk oblast, Russia, located about 90km from Chelyabinsk. It is one of the largest copper smelting centers of the country. For a time, according to UNESCO, Karabash was considered the most polluted city in the world. For decades from the foundation in the beginning of 20th century, the equipment of all the plants producing metals has not changed significantly. The emissions of the plants were not cleaned properly, and as a result, the total weight of emissions was more than 14 million tons.