Samples of domestically produced industrial raw minerals and soil samples from threemining sites of quality ceramic/smelting and pottery industries in Akwa Ibom, Nigeria,were collected and analyzed for their 226Ra, 232Th and40K contents using gamma-ray spectroscopy. The range of activity concentrationsof the radionuclides in the industrial raw minerals were 17.55 ± 1.63 to 80.99 ± 2.61Bq.kg-1 for 226Ra, 7.64 ± 0.77 to 23.94 ± 0.92Bq.kg-1 for 232Th and 63.22 ± 3.43 to 503.90 ± 5.69Bq.kg-1 for 40K, while in the soil samples they variedfrom 2.87 to 34.78 Bq.kg-1, 7.02 to 24.47 Bq.kg-1 and 7.05 to 162.81Bq.kg-1 for 226Ra, 232Th and 40K,respectively. These results, along with the estimated absorbed dose rates, annualeffective dose rates, radium equivalent(Raeq), external hazard index(Hex), internal hazard index(Hin) and representative of the gamma index(Iγg) are presented. The results obtainedwere below the internationally accepted safe limits. Therefore, the analyzed samples couldbe used in the local industries in the area as component raw materials and/or as buildingmaterials. Also, the mining activities of these minerals in the area have notsignificantly affected the natural radiation dose levels in the area, hence the resultingdose to the population is therefore considered generally low.

The activity concentrations of 226Ra, 232Th and 40K infifty granite samples collected from five different quarry industries in Ondo State,Nigeria, were determined using gamma-ray spectrometry. The mean activity concentrationsfor each industry ranged from 16.7(6.4) to 85.4(23.0), 62.4(10.1) to 113.6(7.6), and1315(136) to 1551(84) Bq.kg-1 for 226Ra, 232Th and40K, respectively. The values in parenthesis are the standard deviations.When compared with results from some parts of the world, the 226Ra and232Th contents were lower, whereas the 40K content was similar.Using different approaches to estimate the potential radiological hazard of the samples,the results obtained were below the recommended maximum limits. This shows that theradiological hazards associated with the use of the granites examined in this study asbuilding material are within the acceptable limit.

Bitumen samples and soil samples around a bituminous deposit in Ondo State, Nigeria, wereanalysed for 40K, 226Ra and 232Th employing gamma-rayspectrometry. The activity concentrations of 40K, 226Ra and232Th in soil varied from (45.2 ± 5.3) to (484.2 ± 25.9), BDL (belowdetectable limit) to (27.7 ± 2.1) and (22.8 ± 2.7) to (62.4 ± 6.8) Bq.kg-1,respectively. The corresponding mean values were (240.2 ± 133.5), (13.3 ± 8.0) and (40.0 ±10.2) Bq.kg-1, respectively. The mean activity concentrations of theradionuclides in the bitumen were (58.4 ± 36.4), (16.1 ± 13.3) and (32.5 ± 13.1)Bq.kg-1, respectively, for 40K, 226Ra and232Th. The mean absorbed dose and effective dose for the soil samples were(41.5 ± 8.9) nGy.h-1 and (50.7 ± 10.9) μSv.y-1, respectively, whilethose of the bitumen samples were (29.5 ± 15.6) nGy.h-1 and (36.1 ± 19.1)μSv.y-1, respectively. For radiological hazard assessment, the radiumequivalent activity and the external hazard index were determined. The values of theradium equivalent activity and external hazard index obtained for the soil and bitumensamples were lower than the recommended limit.

Natural radionuclide concentrations in soil samples collected within and around crude oilflow and gas compression stations in the Niger Delta, Nigeria, were determined usinggamma-ray spectroscopy. The mean activity concentrations of 40K,238U and 232Th varied from 30.1 ± 3.0 to 59.0 ± 17.1, BDL to 8.8 ±2.3 and 7.9 ± 3.7 to 10.9 ± 1.9 Bq.kg-1, respectively. The 40K,238U and 232Th contents of the soil samples are very low comparedwith the world average for natural background area. The absorbed dose rate and effectivedose ranged from 6.9 to 11.1 nGy.h-1 and 8.5 to 13.6 μSv.y-1,respectively. The annual gonadal dose equivalent rate ranged from 48.9 to 77.5μSv.y-1, which is lower than the world average of 0.30 mSv.y-1.The radium equivalent activity and the external hazard index of the soil samples werebelow the recommended limits of 370 Bq.kg-1 and unity, respectively. Theresults obtained reveal that there is no significant radiation hazard due to naturalradionuclides of the soil samples in the studied areas.

The activity concentrations of potassium, uranium and thorium in minerals and soilsamples from a mining site in Ibadan, Southwestern Nigeria were measured using gamma rayspectroscopy method. Effective dose per annum has been calculated from the activityconcentrations of dominant gamma-emitting natural radionuclides, potassium, uranium andthorium. Samples collected include minerals (beryl, quartz and feldspar), soil samplesfrom the mining pits, heaps and undisturbed land around the mining site. The activityconcentrations of 40K, 238U and 232Th, respectively in Bqkg-1 in the mineral samples were as follows: 1985 ± 16, 4.8 ± 0.9 and 11.8 ±5.8 for beryl sample, 115.1 ± 27.9, 5.0 ± 1.3 and 6.3 ± 5.0 for feldspar samples and 1421± 122, <4.8 and 20.1 ± 3.5 for quartz samples. For the soil samples, the meanactivity concentrations of 40K, 238U and 232Th,respectively, were 314.2 ± 5.7, 27.7 ± 2.6 and 11.5 ± 5.9 Bq kg-1 for soilsamples from the pits and 278.1 ± 5.4, 21.1 ± 2.0 and 15.3 ± 7.5 Bq kg-1 forsoil samples from heaps. The mean activity concentrations of soil samples from theundisturbed land around the mining site were 194.3 ± 25.2, 14.5 ± 5.1 and 13.3 ± 5.9 Bqkg-1 for 40K, 238U and 232Th, respectively.The effective dose to which the miners are exposed according to exposure scenarios werecalculated as 89.9 μSv y-1 for digging and handling of soil and mineral samplesin the pit and 63.6 μSv y-1 for handling of soil and mineral samples at theheaps.

Farming on soils situated in high background radiation areas can result to enhanced radiation exposure scenarios and pathways to humans. To assess the likely levels of exposures, farm soil samples were collected from different farmlands in three old tin mining localities (Bitsichi, Bukuru and Ropp) in Jos Plateau Nigeria, known for high radiations. The soil samples were analyzed for the activity concentrations of 226Ra, 232Th and 40K, using gamma-ray spectroscopy. The outdoor annual effective dose rates were calculated using the activity concentrations of the radionuclides and were found to vary from 0.07 mSv to 2.02 mSv across the three localities. Considering dust generation from soil tillage and inadvertent ingestion of soil particles, the likely internal radiation hazards were estimated using conservative dust and soil loading factors. The total average annual effective dose rates due to 226Ra and 232Th that could result from dust inhalation and ingestion of soil particles were 16.9 µSv, 8.1 µSv and 8.8 µSv, respectively for Bitsichi, Bukuru and Ropp. Though these values are about 5% the outdoor exposures to the farmers in those farms and greater than 1 µSv y-1, from the point of view of radiation protection and risk, they are significant. It suffices to say, therefore, that the results of this study will create the possibility of the importance to evaluate the health risk among the farming population and workplace environments which often is not covered by regulations concerning health protection.

The radionuclide contents in waste products and physico-chemical characterization of effluent samples from some selected industries in the city of Lagos were carried out. The radioactivity concentration levels due to 40K, 226Ra and 228Th in the solid wastes were determined using gamma-ray spectrometry while physico-chemical determination of parameters were based on standard methods of measurements. The average radioactivity levels obtained was between 104 ± 14 Bq kg-1 and 1276 ± 31 Bq kg-1 for 40K, 86 ± 18 Bq kg-1 and 122 ± 23 Bq kg-1 for 226Ra and while for 228Th it ranged between 14 ± 2 Bq kg-1 and 73 ± 10 Bq kg-1. No artificial radioactive elements were detected in any of the samples. The average outdoor effective dose rate due to gamma exposure from these waste materials in the city was calculated as 0.12 mSv y-1. This is far less than 1 mSv y-1 recommended limit for the member of the public by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The pH of the effluent samples was slightly alkaline, while the electrical conductivity ranged between 275 and 455 µS cm-1 and total suspended solids ranged from 104 to 5616 mg l-1. All these ranges and those of biochemical and chemical oxygen demand values were all higher than the prescribed limits. Presence of heavy metals in the effluent samples was however lower than prescribed with the exception of iron.

A low cost in-situ gamma-ray spectrometric method for rapid assessment of radiation exposure, identification of radionuclides and detection of changes in environmental radioactivity has been employed in the determination of the natural gamma radiation dose levels in six major cities of the southeastern region of Nigeria. The soil radioactivity concentrations of the primordial radionuclides; 40K, 238U and 232Th were determined and have been related to the γ-dose rates in the cities. The activity concentration of 40K across the region ranged between 0.021 and 0.200 kBq kg–1; 238U was between 0.001 and 0.066 kBq kg–1 while that of 232Th ranged between 0.015 and 0.103 kBq kg–1. The total γ-absorbed dose rates in air in the region ranged between 0.016 and 0.090 μGy h–1 with a mean of 0.039 ± 0.018 μGy h–1. The mean of the annual outdoor effective dose due to the terrestrial gamma radiation for the region was calculated as 50 μSv y–1 representing 66% of the world average value.