Natural radioactivity and dose assessment for phosphate rocks from Wadi El-Mashash and El-Mahamid Mines, Egypt Adel G.E. Abbady a , M.A.M. Uosif b , A. El-Taher b, * a Physics Department, South Valley University, Faculty of science, Qena, Egypt b Physics Department, Faculty of Science, AL-Azher University, Assuit, Egypt Received 11 February 2005; received in revised form 8 April 2005; accepted 11 April 2005 Available online 13 June 2005 Abstract The activity concentrations of 226 Ra, 232 Th and 40 K have been measured by gamma spectroscopy (sodium iodide NaI(Tl) detector) in phosphate rock samples, collected from the Wadi El-Mashash, a site located in the central eastern desert, and El-Mahamid in the Nile valley, Egypt. The average activity concentrations of 226 Ra, 232 Th and 40 K (Bq kg ÿ1 ) in phosphate rocks were 665.8 G 33.4, 329.4 G 17 and 587.6 G 29.4 for Wadi El-Mashash and 566.8 G 28.6, 217.3 G 11.8 and 560.1 G 28 for El-Mahamid, respectively. The corresponding values for shale rocks were 85.2 G 5.7, 93.3 G 5.6 and 303.1 G 15.2 Bq kg ÿ1 , respectively. As a measure of radiation hazard to the occupational workers and public, the Ra equivalent activities, representative level index and dose rates due to natural radionuclides at 1 m above the ground surface were estimated. The calculated external g-radiation dose received by the workers of the phosphate mine are 538 and 418 mSv/y, which is far below the permitted dose of 20 mSv/y recommended by the International Commission of Radiation Protection [ICRP-60, 1990. Radiation Protection: 1990 Recommendation of the International Commission on Radiological Protection, Oxford, Pergamon Preis.] for workers. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Natural radioactivity; Dose assessment; Phosphate rocks * Corresponding author. Tel./fax: C20 88 2325436. E-mail address: atef_eltaher@hotmail.com (A. El-Taher). 0265-931X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jenvrad.2005.04.003 Journal of Environmental Radioactivity 84 (2005) 65e78 www.elsevier.com/locate/jenvrad