Why do people quoting half lives always get excited about big numbers?  Hydrogen has a halflife of somewhere around 30 billion years!  Scary stuff.<br>To be honest I'd rather spend an hour in a room with a kg of platonium with a half life of 120,000 yrs than spend 2 seconds in a room with a few grams of Strontium90 or Cesium 137 with half lives measured in days or months.<br>The LOWER the half life the more dangerous the substance, the more curies per minute it will release, the more damage it will do.