RISK DUE ASSESSMENT TO THE INTAKE OF URANIUM ISOTOPES IN MINERAL SPRING WATERS

Objective To complement the data of a previous research concerning the evaluation of the lifetime risk of radiation-induced cancer due to th e ingestion of Ra-226, Ra-228 and Rn-222 in mineral spring waters from a natural highly radioactive region of Brazil. The study was performe d to evaluate the lifetime risk of radiation-induced cancer due to the ingestion of U-238 and U-234 in the same spring waters. Method It is assumed that the risk coefficient for natural isotopes is the same as for the Ra-226-induced bone sarcomas and that the equilibrium for skel etal content is 25 times the daily ingestion of Ra-226, but II times t he daily ingestion of long-lived uranium isotopes. Waters samples were collected seasonally over a period of one year at all the spring site s used by the local population of Aguas da Prata, S. Paulo State (Braz il). Results Concentrations ranging from 2.0 to 28.4 mBq/L and from 4. 7 to 143 mBq/L were observed for U-238 and U-234, respectively. Based upon the measured concentrations the lifetime risk due to the ingestio n of uranium isotopes was estimated. A total of 0.3 uranium-induced ca ncers per 10(6) exposed persons was predicted, suggesting that chronic ingestion of uranium at the levels observed at these springs will res ult in an incremental increase of fatal cancers of 0.1%. Conclusions B y taking into account the uncertainties in evaluating the carcinogenic effects, it can be concluded that virtually no cancer would be expect ed from the ingestion of uranium in the mineral spring waters analyzed .