After 25 years, some of Chernobyl’s radioactive substances have either decayed or migrated deeper into the ground. Although levels of cesium-137 are slowly falling, concentrations of the damaging bioactive element remain high in many areas.

SOURCES: International Atomic Energy Agency, CIA, Epidemiologic Reviews, University of Pennsylvania, | GRAPHIC: By Patterson Clark and Gene Thorp/The Washington Post April 4, 2011
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