closed in 1991. From 1996 to 2012, a secret joint operation of Kazakh, Russian, and American nuclear scientists and engineers secured the waste plutonium in the tunnels of the mountains. See also Health effects of pollution Japanese nuclear disaster, Fukushima Goiânia accident Chernobyl disaster and Chernobyl disaster effects List of most-polluted cities by particulate matter concentration Three Mile Island accident and Three Mile Island accident health effects Cuban Missile Crisis SL-1 nuclear meltdown References Air pollution Soil contamination Radioactive contamination