August 29 marks 32 years since Kazakhstan closed the Semipalatinsk nuclear test site, a remote area that was used by the Soviet Union for hundreds of atmospheric and underground nuclear tests over a period of 40 years. Nuclear weapons testing resulted in the radioactive contamination of an area of over 18,300 square kilometers. August 29 is also the International Day against Nuclear Tests, and the United Nations General Assembly and European Union have led calls for all nuclear powers to sign the Comprehensive Nuclear-Test-Ban Treaty.