In household water the most harmful radiation exposure substance is radioactive radon.
Drilled wells aerosolize radon gas which increases risk for cancer.
The most common radioactive source in water is radon (Rn222). In Finland there are places where radon levels are naturally high, such as ridge areas. Radioactivity in drilled wells water is clearly higher than in other European countries.
Radon levels in Finnish waterworks is on average about 26 Bq per litre and it may be considered as an excellent result. In ring wells radon levels are on average about double compared to water works. Water from drilled wells has on average radon levels of 460 Bq/l. Drilled well water is used daily by over 200 000 Finnish and more than 10 % of them uses water that has radon levels over 1 000 Bq/l.
Disadvantage of radon in drilled well water is possible to detect only by radon measurement of water. One should react if radon levels are over 600 Bq/l. Radon in water rises radon levels in indoors air.
Radon measurements is reasonable to do at your home and free-time habitation.