Cs-137 has a half life of 30 years, so yes, it is the longer term risk. However, the "biological half-life" of cesium is only about 70 days [1], so it leaves t

Cs-137 has a half life of 30 years, so yes, it is the longer term risk. However, the "biological half-life" of cesium is only about 70 days [1], so it leaves the body relatively quickly. http://en.wikipedia.org/wiki/Cs-137#Health_risk_of_radioactive_caesium http://en.wikipedia.org/wiki/Cs-137#Health_risk_of_radioacti...