Natural reactor at Oklo in Gambon, Africa( Illonois energy prof) found the fission products do no migrate far through the water table. Thorium and U238 have longer half lives so is that really dangerous. The longer the half life the safer they are. Remember we use to use Uranium for luminous dials and thorium in the old tilly lamps. (before you mention the radium women, we don't lick paint brushes used on oil based paint or used in parts washers either. Cyanide, arsenic are dangerous forever but we don't panic about that for people to find in the future. Some fission products become harmless after some minutes. Might be attributed is a pretty broad statement. A lot of the publics perception is a fall out of the cold war among older generations that went through the cold war. I use to think the same.