Misasa Onsen is one of the world’s famous radioactive hot springs containing a high radon concentration. Radon is a weak radioactive substance produced by the decay of radium. Low doses of radon exposure improve the metabolism and boost the body’s immunity and natural healing power. These are the special “hormesis” effects.
Additionally, when inhaled, radon enhances the body’s antioxidant function, which supports anti-aging and prevention of lifestyle-related diseases. This mineral-rich spring water is also good for drinking.(retrieved Sept 6, 2018 from http://spa-misasa.jp/eng/radium/)

  Mattis, Vitae