Uranium in the environment resulting in workers exposed to high levels of radiation. Conventional uranium ore treatment mills create radioactive waste in the form of tailings, which contain uranium, radium, and polonium. Consequently, uranium mining results in "the unavoidable radioactive contamination of the environment by solid, liquid and gaseous wastes". Inhalation of radon gas caused sharp increases in lung cancers among underground uranium miners employed in the 1940s and 1950s. In the 1940s and 1950s, uranium mill tailings were released with impunity into water sources, and the radium leached from these tailings contaminated thousands of miles of the Colorado River system. Between 1966 and
Uranium mining in Colorado oxide. The mine is owned by General Atomics subsidiary the Cotter Corporation, which estimates that there are an additional 16 million pounds (7300 metric tons) of uranium oxide resource remaining in the mine. The Copper King mine, in Larimer County about 25 miles northwest of Fort Collins and 5 miles northeast of Red Feather Lakes contained a skarn deposit that was worked unsuccessfully for zinc in 1920 and 1936. Prospectors found uranium at the abandoned mine in 1949, and it was worked for uranium from 1951 until 1953. The uranium occurs as pitchblende in a hydrothermal vein deposit in Precambrian