There is uncertainty about average and peak levels of radioactivity to which some people are being exposed. Radioactive materials cause harm only when not enough antioxidants are present to soak up the extra electrons (energetic free radicals; oxidative stressors) induced by radioactive particles. Radiation is like a sub-molecular fire. There is a temperature above which even the best fire resisting protective barrier fails. So it is with radioactivity.
Read More: Acting from excess of caution