Natural radionuclides in ground water in Finland

A nationwide survey of the natural radioactivity in drinking water was conducted in Finland throughout the 1970s and has continued in the 1980s with the emphasis on drinking water originating from drilled wells, which may be rich in natural radionuclides (mean 222Rn 1020 Bq.l-1, maximum 77,000 Bq.l-1). Between 1981 and 1987, 3000 ground water samples were analysed for 222Rn, some of them for gross alpha and beta, 226Ra, 210Pb, 210Po and U. In recent years the occurrence of 210Pb and 210Po in ground water has been studied. Preliminary results suggest that the contribution of 210Pb and 210Po to the total annual effective dose equivalent is higher than the contribution of 226Ra or U in that water. (author)