The 226Ra, 232Th and 40K contents in the Abakaliki baked shale construction materials and their potential radiological risk to public health, southeastern Nigeria

Abstract

Natural radioactivity associated with the Abakaliki baked shale as construction materials was measured using gamma spectrometry to establish radiological risk to public health. From the results, the mean activity concentrations of 226Ra, 232Th and 40K are 38.852 ± 2.829 Bqkg–1, 69.589 ± 1.759 Bqkg–1 and 557.667 ± 3.002 Bqkg–1 respectively, higher than the world average concentrations of 35 Bqkg-1, 45 Bqkg-1 and 420 Bqkg–1 respectively. The radiation hazard indices such as air absorbed dose ranged from 67.22 to 108.7 nGyh-1 higher than the world average value of 55 nGyh-1 [United Nations Scientific Committee on the Effects of Atomic Radiation, UNSCEAR]. The annual effective dose which ranged from 0.08 to 0.13 mSvy-1 are less than the annual effective dose limit [E] of 1.0 mSvy-1 for humans. The Radium equivalent activities [Raeq] [146.23 -234.59 Bqkg1] are below UNSCEAR recommended limit of 370 Bqkg-1. The internal [0.410-0.740] and external [0.393-0.640] radiation hazard indices are less than unity which is the world permissible value. The gamma activity indexes correspond to an activity concentration index of 2 ≤ Iγr ≤ 6 proposed by European Commission. The annual gonadal equivalent dose [AGED] average value of 537.53 mSvy-1 is higher than the world average value of 300 mSvy-1. On average, studied shales satisfy most of the health risk indices such as E and Raeq as well as the radiation hazard indices as their mean values are lower than the permissible limits. The use of these construction materials is free of any health risk related to radiation.