2005 longitudinal study in the Journal Science:A Cold War environment calamity appears to be the cause of a spate of cancers in the Russian heartland. A landmark study this month by US and Russian scientists blames excess cancers in the Ural Mountains on chronic exposures to radioactivity leaked from a weapons plant a half-century ago. The study is the latest blow to the notion that there is a threshold of exposure to radiation below which there is no health threat.