A nationwide study on the natural radioactivity of drinking water has been made in Finland. The study was directed mainly at drinking water distributed by water supply plants with more than 200 users. Additional samples were collected from private dug and drilled wells. The samples were analysed for 222Rn, 226Ra, gross alfa- and gross beta-activity. Half of the samples collected from drilled wells were analysed for uranium as well. The radioactivity of drinking water distributed by the water supply plants was on the average low, the mean concentration being 670 pCi/l. for 222Rn and 0.1 pCi/l. for 226Ra. The most radioactive water was found in drilled wells, in which the mean concentrations were 17,000 pCi/l. for 222Rn and 2.9 pCi/l. for 226Ra. Some of the drilled wells also had abnormally high concentrations of uranium, up to 2100 μg/l. and even higher in some wells in the Helsinki region.
©1980Health Physics Society