Title:
Natural radioactivity in tap water and associated age-dependent dose and lifetime risk assessment in Amman, Jordan.

Abstract:
With the aim of assessing potential public impact, preliminary investigations on tap waters collected from highly populated areas in Amman and Aqaba, Jordan were conducted by measuring gross alpha and beta activities as well as uranium and radium radionuclides. Gross activities deduced by liquid scintillation counting (LSC) were ranged in <50-250 ± 23 mBq l(-1) for alpha and <188-327 ± 29 mBq l(-1) for beta in Amman whereas higher concentrations were found in Aqaba. The results show that gross β activities are generally higher than the corresponding gross α activities and direct correlations between gross activities and total dissolved solids (TDS) exist. Moreover, the effect of TDS on gross analyses was studied and devoted to the optimization of LSC parameters. (234)U, (235)U and (238)U concentrations were determined by alpha spectrometry after separation from the matrix by extraction chromatography and electroplating. (226)Ra and (228)Ra concentrations were measured, respectively, using de-gassing and gas proportional counter techniques. Uranium and radium concentrations do not reach the WHO recommended levels and the radioisotopic activity ratios were discussed. The associated age-dependent dose from water ingestion in Amman was estimated. The total dose for adults had an average value of 0.15 mSv y(-1), which exceeds the WHO recommended limit of 0.1 mSv y(-1) but still below the Jordanian limit of 0.5 mSv y(-1). Although the Jordanian limit was exceeded for babies and infants, the lifetime risk assessment showed values as low as 10(-4). Thereby it is concluded that tap waters of Amman is radiologically safe and pose no significant hazard to the public. Finally, a comparison of the investigated waters with worldwide data was made.