Health effects guidance for uranium in drinking water.

The interim regulations for radioactivity in drinking water were promulgated in 1976 (Federal Register, Friday, 9 July, 1976, p. 28402). These regulations specifically excluded uranium because of uncertainties concerning its toxicology, treatment technology and occurrence. At this time, EPA's Office of Drinking Water is considering proposing a health effects guidance level of 10 pCi/l. (0.37 Bq/l.) for uranium in drinking water. This paper describes the approach that EPAs Office of Drinking Water is considering in developing the guidance level. This value has not yet been officially determined to be EPA's formal guidance, but is presented as a working hypothesis for review and comments. Included here is a discussion of occurrence, pharmacokinetics and health effects. The calculation of doses uses the ICRP 30 model and the risk determination uses EPA's newly developed life table approach. The risk level from ingesting drinking water with a uranium content of 10 pCi/l. is estimated to be about 3 X 10(-5) excess cancers/lifetime.