a b s t r a c tThe activity concentration of 226 Ra, 232 Th and 40 K was measured in commonly building materials used in Nigeria from commercial supplier using High Purity Germanium Gamma (HPGe) detector. The mean activity concentrations in the samples were found to be 51.5 ± 9.3, 72.46 ± 17.65 and 217.05 ± 44.31 Bqkg À1 for 226 Ra, 232 Th and 40 K respectively. The highest radium equivalent (Ra eq ) of 273.9 Bqkg À1 was noted in Perfect Superfix White Cement (Nigeria) but found to be < 370 Bqkg À1 as the recommended dose limiting safe value for bulk media as presumed, the highest value of internal hazard index (H in ) and external hazard index (H ex ) of 0.894 and 0.744 respectively were also < 1. The absorbed dose rate (DR) with a value of 122.52 nGyh À1 noted in ceramic tile sample is higher than the weighted population world average value of 80 nGyh À1 by a factor of 1.53. The highest annual effective dose rate (AEDR) of 0.601 mSvy À1 reported in PNT ceramics but was found to be less < 1 mSvy À1 . The investigated materials have the values of H in , H ex and AEDR greater than 0.5 but less than1, showing that the dose impact exceeds the exemption dose level of 0.3 mSvy À1 for AEDR but complies to the upper limit of dose principle of 1 mSvy À1 .

Graphical abstract

In this investigation, natural radioactive contents in tiles manufactured in Nigeria and tiles imported from China were measured using gamma ray spectroscopy. High Purity Germanium detector was used to estimate the concentrations of some radioisotopes present in 17 samples of various tiles from Nigeria and China. The average activity concentrations of 226Ra, 232Th, and 40K for the tiles were found to be 68.2 ± 0.5; 173.9 ± 9.2 and 490 ± 15 Bq/kg and 58.2 ± 0.5, 161.5 ± 9.4 and 455.7 ± 15.1 Bq/kg for the tiles from Nigeria and China respectively. Radiological hazard indices such as absorbed dose rate, radium equivalent activity, external Hazard Index (Hex), internal Hazard Index (Hin), Annual Effective Dose (mSv/y), Gamma activity Index (Iγ) and Alpha Index (Iα) were determined for both kind of tiles from Nigeria and China. The mean values obtained were: 354.56 and 317.16 Bq/kg; 169.22 nGyh−1 and 153.92 nGyh−1; 0.95 and 0.87; 1.14 and 1.08; 1.59 mSv/y and 1.52 mSv/y; 1 and 1.15 and; 0.34 and 0.29 respectively. The mean value of radium equivalent obtained in this study is less than that of the international reference value of 370 Bq/kg for the both kind of tiles.

Natural radioactivity in coastaline area soil of Ado-Odo/Ota has been carried out to ascertain the presence of radionuclides using gamma-ray spectroscopy (HPGe detector). The result showed that U-238, Th-232 and K-40 ranged from 24 ± 7–49 ± 10; 67 ± 6–120 ± 9 and 88 ± 17–139 ± 20 Bqkg−1 respectively. The radium equivalent for the samples ranged from 132.51 to 230.91 Bqkg−1 with mean value of 185.89 Bqkg−1. The mean value for the gamma dose rate for the soil samples was estimated to be 81.32 nGyh−1. The estimated values of annual effective dose equivalent ranged from 0.61 to 1.07 mSv y−1. The estimation of alpha index representative (Iα) ranged from 0.12 to 0.24 with mean value of 0.21 while the gamma representative index ranged between 0.465 and 0.810. The activity utilization index of the soil samples ranged from 1.09 to 1.89 with mean value of 1.53. The radiological implication in the study area has shown that the soil samples with gamma dose rate value of 89.99 nGyh−1, 94.39 nGyh−1, 97.40 nGyh−1 and 101.04 nGyh−1 respectively are higher than the recommended value of 80 nGyh−1 and may pose health implication for long term exposure.

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