Many hundreds of thousands of people -- athletes and spectators -- will flood into Japan for the 2020 Olympics. But exposure dangers from the Fukushima nuclear catastrophe have not ended since the meltdowns and explosions spread radioactive material over large areas reaching down to Tokyo and beyond. Soon after the start of the meltdowns, experts began warning of exposure to radioactive microparticles (hot particles) -- a type of particle that poses a danger unaccounted for by regulatory agencies. What are the implications for people coming to the Olympics, and for those who have been there and will remain, once the games have concluded? More