The activity concentration of radon in well water ranged from 12.4 ± 1.29 to 17.0 ± 1.67 Bq/l with an average of 14.7 ± 1.44 Bq/l, whereas that in stream and tap water ranged from 6.7 ± 0.86 to 9.4 ± 0.88 Bq/l with an average of 7.9 ± 0.86 Bq/l and 2.7 ± 0.31 to 7.0 ± 0.71 Bq/l with