Chernobyl

 But now there's growing evidence and argument from experts in radiology, that long-term exposure to low-levels of radiation may actually be beneficial to your health.

Which would explain why the residents of Ramsar in Iran, with a background radiation level of an astounding 250 mSv per year, have lower cancer rates than the world average.

-> Radiation in Japan: Are You Still at Risk From Fukushima? (worldnomads.com)