Estimates of cancer mortality due to the ingestion of mineral spring waters from a highly natural radioactive region of Brazil

This study was performed in order to evaluate the lifetime risk of radiation-induced cancer due to the ingestion of 226Ra, 228Ra and 222Rn in mineral spring waters from a highly natural radioactive region of Brazil. Water samples were randomly collected at 10 spring sites located in the Águas da Prata region. Concentrations ranging from < 2.2 to 1.80 × 103 mBq l−1 for 226Ra, < 3.7 to 2.3 × 101 mBq l−1 for 228Ra and 8 × 10−1 to 2.16 × 102 Bq l−1 for 222Rn were observed. A total of eight radium-induced cancers (four head carcinomas plus four bone sarcomas) per 106 exposed persons were predicted. For radon, a total of 23 cases of fatal stomach cancers per 106 exposed persons were estimated. These predictions suggest that chronic ingestion of radium and radon at the levels observed at these springs will result in incremental increases of fatal cancers of 2 and 0.5%, respectively, above the background incidence rate. The uncertainties in evaluating the carcinogenic effects due to radium and radon ingestion were analyzed. These investigations suggest that the true risk due to radium ingestion is likely to be within an order of magnitude in either direction of the risk estimated in the present paper.