Natural radioactivity levels in river, stream and drinking water of the northwestern areas of Pakistan

Natural radioactivity in the aquatic media has been determined by collecting samples of river, stream and drinking water from the northwestern areas of Pakistan. The concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th have been measured using a low background gamma-spectrometer and a 10 cm³ planar intrinsic high purity germanium detector. The annual ingestion of these radionuclides, using local consumption rates (average over the whole population) of 0.9 l^.d^-1, were estimated to be 49.2, 6.2 and 1.1 Bq^.y^-1 for ⁴⁰K, ²²⁶Ra and ²³²Th, respectively. A comparison of the annual intakes of these radionuclides, using annual consumption rates of NCRP, ICRP and FBSP shows that the contribution from natural radionuclides to annual intake is slightly greater for NCRP than for ICRP and FBSP consumption rates. However, the estimated values and weighted means of these radionuclides compare well with the world average. The annual effective dose equivalent from drinking water was found to be 3.6^.10^-6 mSv^.y^-1 (²²⁶Ra), 3.2^.10^-12 mSv^.y^-1 (²³²Th) and 2.1^.10^-6 mSv^.y^-1 (⁴⁰K). These values are lower than those given by NCRP.