External exposures of population to ionising radiation due to naturally occurring radionuclides in sixty-three granite samples from three different locations in south eastern desert of Egypt were considered in this article. Average outdoor gamma dose rates in air were 190, 290 and 330 nGy h(-1) for Elba, Qash Amir and Hamra Dome granites, respectively. The corresponding doses in indoor air are 270, 400 and 470 nGy h(-1), respectively. These average values give rise to annual effective dose (outdoor, indoor and in total) 0.24, 1.4 and 1.6 mSv for Elba granite. For Qash Amir and Hamra Dome granites the corresponding values were 0.35, 2 and 2.3 mSv and 0.41, 2.3 and 2.7 mSv, respectively.

The concentrations of the natural radionuclides (226)Ra, (232)Th and (40)K in 15 different water samples from Elba protective area, south-eastern desert of Egypt, have been determined using NaI(Tl) detector. Gamma ray spectrometric analysis was performed and the concentrations obtained for each of the radionuclides expressed in Bq l(-1) ranging from 1.6 to 11.1 for (226)Ra, 0.21 to 0.97 for (232)Th and 9.1 to 23 for (40)K. A reasonable correlation was found between (226)Ra, (232)Th concentrations and pH, although no general trend was observed with conductivity and total dissolved solids. The mean effective doses of 0.56 mSv y(-1) for (226)Ra, 0.065 mSv y(-1) for (232)Th and 0.04 mSv y(-1) for (40)K were estimated for the ingestion of these waters by adults.

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Natural radioactivity due to the presence of 226Ra, 232Th and 40K in selected building materials (cement, sand, bricks, gypsum and ceramic) used in Egypt was measured using a gamma-ray spectrometer with an HPGe detector. The average activity concentrations observed in different building materials ranged from 10.0 +/- 1.3 to 109 +/- 6, <2 to 55.8 +/- 2.2 and 5.5 +/- 1.7 to 684 +/- 34 Bq kg(-1) for 226Ra, 232Th and 40K, respectively. Based on these, together with previously reported results, the effective doses received by the residents of different types of house within all Egyptian governorates were assessed using the WinMat computer program. The results were below 1 mSv a(-1) in all cases. The collective effective dose indoors was assessed as 15,000 man Sv and the excess effective dose due to building materials was 0.07 mSv a(-1).

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