this is the scene at one shelter in sendai, japan where victims are still coping with their losses after the earthquake and tsunami devastated this region. at least 160 people living near japan's troubled power plant have been exposed to high levels of radiation and after new cooling problems just today, more radioactive steam will have to be released. senior medical correspondent elizabeth cohen has been following developments for us. how much do we know about the kind of radiation that these people are being exposed to? >> there's a lot that we don't know. and i'm glad you asked about the kind of radiation, because people often think radio activity is radio activity but different things affect people