Most household waters below the safety limits

According to guidelines published by the Finnish Centre for Radiation and Nuclear Safety, the radiation dose caused by radioactivity in household water shall not exceed 0.5 millisieverts a year. Most of the water distributed by Finnish waterworks meets this safety goal. According to measurements performed to date, only 20-30 small waterworks or water intake plants have exceeded the limit. Radioactivity in excess of the safety goal is almost invariably caused by a high radon concentration. When ingested, radon causes a radiation dose to the organism; the lungs are also affected when radon is released into the air and then inhalated. Privately owned bored wells, however pose a problem, because the radioactivity of water in some Finnish wells is among the highest in the world. If the same 0.5 millisievert limit was also applied to wells bored for private use, the safety goal would be exceeded by more than half of the wells. (orig.)