As a practical example, the aboriginal people of Australia (particularly in the north) refer to a thing called "sickness country": http://www.artistwd.com/jo

As a practical example, the aboriginal people of Australia (particularly in the north) refer to a thing called "sickness country": http://www.artistwd.com/joyzine/australia/abr_culture/sickness_country.php These have generally been found to be regions with a lot of near surface uranium ore. Given enough time, people will figure out that certain areas are dangerous and should be avoided. As long as it's not everywhere, it probably won't threaten the whole of humanity.