Chernobyl and Fukushima had highly publicized nuclear events. Both governments cleaned up the areas, but doubts remain. Mashable published an article with exhibits by, "Greg McNevin, a photographer working with the environmental group Greenpeace, set out to visualize the radiation that persists in many of these areas."
"Using a programmable LED rod that when connected to a Geiger counter (a device that measures ambient radiation) translates the analog signal into a light display, McNevin walked through long exposure photographs he was taking of affected areas, showcasing the live radiation data his counter was reading."
Here is one of the photos, you see the radiation, likely tracked by shoes leading up to a school.
How dangerous is the radiation? Don't know. But would you want your kid to be attending that school? Probably not. Powerful perception management. Read the article, it is well done.