Natural radionuclides in drinking water supplies of São Paulo State, Brazil and consequent population doses

Abstract

The activity concentrations of 228 Ra , 226 Ra and 222 Rn have been analysed in 452 drinking water supplies of São Paulo State. This study started in 1994 and covered 54% of the 574 existing counties. Concentrations up to 235 and 131 mBq l −1 were observed for 226 Ra and 228 Ra , respectively, whereas 222 Rn concentrations reached 315 Bq l −1. Radiation doses up to 0.3, 0.6 and 3.2 mSv yr −1 were estimated for the critical organs, for the ingestion of 226 Ra , 226 Ra and 222 Rn , respectively. The corresponding committed effective doses reached values of 6×10 −3, 2×10 −2 and 3×10 −1 mSv yr −1, for the same radionuclides. These results indicate that 222 Rn makes the highest contribution to the total effective dose.