Determination of Radiological Health Hazard Indices in Selected Crude Oil Spilled Environment in Rivers State, Nigeria.

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1 AMERICAN JOURNAL OF SCIENTIFIC AND INDUSTRIAL RESEARCH 2016,Science Huβ, ISSN: X, doi: /ajsir Determination of Radiological Health Hazard Indices in Selected Crude Oil Spilled Environment in Rivers State, Nigeria. 1*. Anekwe, U.L., 2 Avwiri, G.O. 1 Department of Physics, Federal University Otuoke, Bayelsa State, Nigeria. *Corresponding Author 2 Dept. of Physics, University of Port Harcourt, Choba, Rivers State, Nigeria. ABSTRACT The determination of radiological health hazard indices in some selected crude oil spilled sites in Rivers state, Nigeria has been carried out using NaI (TI) Ɣ spectroscopy followed by mathematical computations. The analysis of percentage contributions of 226 Ra, 232 Th, and 40 K to the health risks of radium equivalent revealed that 226 Ra has the highest percentage contributions in four out of the five oil spilled sites, and was low at Mgbede. Health hazard indices of radium equivalent, excess lifetime cancer risk, and annual gonadal equivalent dose ranged from 87.05±3.93 Bqkg -1 to ±9.06 Bqkg -1, 0.21x10-3 to 0.39x10-3, to respectively. I-gamma index ranged from 0.57 to 1.40 Bqkg -1. The external and internal hazard indices ranged from 0.22 to 0.54, and 0.26 to 0.82 respectively. The average absorbed doses ranged from to ngyh -1. The results are above the control samples obtained from similar environment. This showed that the soil, water and the environment have some levels of anthropological radiological degradation. Therefore the crude oil spilled areas should be minimally used especially by farmers and herdsmen to avoid intake of radioisotopes. INTRODUCTION The need for healthier environment has been on the increase as a result of human population growth and numerous activities of man on planet earth. This has reawakened the environmental consciousness of human beings especially researchers in the various fields of endeavour including scholars with special interest on the radiological impact that human activities and natural radioactive materials have on the ecosystem. Hydrocarbon exploration and production activities have the potential to increase the risk of radiation exposure to the environment and humans by concentrating the quantities of naturally occurring radiation beyond normal background levels (Ajayi et al, 2009). Naturally Occurring Radioactive Materials (NORMs), such as elements of 238 U, 235 U, 232 Th series and their respective decay daughters, as well as 40 K. NORMs exist in soil, water, plants, animals, human, coal, lignite, petroleum, phosphate ores, geothermal wastes, waste waters et cetera, in small but varying amounts almost everywhere (Attallah et al., 2012). Since Naturally Occurring Radioactive Materials (NORMs) can contaminate the environment and may pose a risk to human health, these risks can be alleviated by the adoption of controls to identify where NORMs are present. This would ensure the reduction or elimination of negative impact on the populace and the environment. It therefore becomes necessary to evaluate the level of induced TENORM that leads to radiological burden on the oil spilled areas in a view to determine the health hazard indices. Wastes associated with the various industrial activities, with enhanced levels of the natural radioactivity as a result of industrial process, cause what is called, Technological Enhanced-Naturally Occurring Radioactive Material (TENORM) and may be injurious to the environment (Attallah et al., 2012). A good example of the high risk associated with oil spill and the high cost of remediation is the case of Ogoni Land (UNEP, 2011). The quest for knowledge of radiation health hazard indices is basically to enable one arrive at a scientific acceptable inferences and conclusion regarding health status and risks associated with impacted environment.increased radiological burden leads to health issues associated with ionizing radiation. 50

2 Fig 1: Map of the study area METHOD A total of thirty soil samples were collected from five different oil spilled sites. The samples were prepared and analysed according to International Atomic Energy Agency standard (IAEA, 2007). The actual measurement of specific activity was done by using sodium iodide detector doped with Therlium,{ NaI(TI)} based on gamma spectroscopy. The measured Average Specific Activity Concentrations were finally used in computing the health hazard indices. The following radiological parameters were calculated from the activities. They are radium equivalent index, representative gamma index, absorbed dose, annual effective dose rate, external hazard index, internal hazard index, excess life time cancer risk and annual gonadal equivalent dose. Fig 2: Typical crude oil polluted land These parameters are factors or limits which define health status of a radiated or irradiated environment and human being. Radium equivalent activity index (Ra eq ) This is a radiological index which represents the activity levels of 226 Ra, 232 Th and 40 K by a single quantity and also takes into account the radiation hazards associated with them (Diab et al., 2008). It is mathematically defined by (UNSCEAR, 2000) as Ra eq = C Ra C Th C K (1) where C Ra, C Th and C K are the activity concentrations of 226 Ra, 232 Th and 40 K respectively. In the above relation, it has been assumed that 10 Bqkg -1 of 226 Ra, 7 Bqkg -1 of 232 Th and 130 Bqkg -1 of 40 K produce equal gamma dose. The maximum value of Ra eq in soil 51

3 must be less than 370 Bqkg -1 (Zarie, 2010) otherwise it is regarded as being above standard. Representative level index (I ): Representative level index is the estimation of gamma radiation associated with the natural radionuclides in the soil. It is defined as (Alam et al., 1999). I = C Ra /150 + C Th /100 +C K / (2) and the standard safety value for this index is 1 Absorbed dose rate (D): Absorbed dose rate is a measure of energy deposited in a medium by ionizing radiation. It is equal to the energy deposited per unit mass of the medium, and so has the unit J/kg, which is given by special name Gray (Gy). Absorbed dose rate therefore is absorbed dose divided by the time it takes to deliver that dose unit Gy/s. The absorbed dose rates in outdoor (D) due to gamma radiations in air at 1m above the ground surface for the uniform distribution of the naturally occurring radionuclides ( 226 Ra, 232 Th and 40 K) were calculated based on guidelines provided by (UNSCEAR, 2000). The conversion factors used to compute absorbed - dose rate (D) in air per unit activity concentration in (dry weight) corresponds to ngh -1 for 226 Ra (of U series), ngh -1 for 232 Th and ngh -1 for 40 K (UNSCEAR, 2000; Ashraf et al., 2010). D (ngh -1 ) = 0.462C Ra C Th C K (3) Annual effective dose rate: To estimate the annual effective dose rates outdoor, the conversion coefficient from absorbed dose in air to effective dose (0.7Sv.Gy -1 ) and outdoor occupancy factor (0.2) proposed by (UNSCEAR, 2000) are used. Therefore, the annual effective dose rate (msv.y -1 ) was calculated by the formula (UNSCEAR, 2000): Effective dose rate ( ) = D (ngh -1 ) x 8760h. yr -1 x 0.7 x (10 3 msv/10 9 ) ngh x 0.2 E ff dose = D x x 10-3 (4) UNSCEAR, 1993, stated that the worldwide annual effective dose from the natural sources of radiation in areas of normal background ionizing radiation is estimated to be 1 msvy -1. External hazard index (H ex ): External hazard index is a widely used hazard Index which represents the external exposure and it is defined by UNSCEAR, 2000 as H ex = C Ra /370 + C Th /259 + C K /4810 (5) Internal hazard index (H in ): In addition to external hazard index, radon and its short-lived products are also hazardous to the respiratory organs. The internal exposure to radon and its daughter progenies is quantified by the internal hazard index H in, which is given by the equation; H in = C Ra /185 + C Th /259 + C K /4810 (6) The values of the indices (H ex, H in ) must be less than unity for the radiation hazard to be negligible (Diab et al., 2008). Excess lifetime cancer risk (ELCR): This is potential carcinogenic effects that are characterized by estimating the probability of cancer incidence in a population of individuals for a specific lifetime from projected intakes and exposures. This was calculated using mathematical expression of equation 3.18 (Taskin et al, 2009). ELCR = AEDE x DL x RF (7) where AEDE is the annual effective dose equivalent, DL is the average duration of life (assumed to be 70years) and RF is the risk factor (fatal cancer risk factor which is 0.05). Annual gonad equivalent dose (AGED): This is a measure of threat to sensitive cells from exposure to a particular level of radiation. These sensitive cells include the gonads, surface cells and the bone marrow. Annual gonadal equivalent dose is calculated using the equation (Ajibode et al., 2013). AGED ( ) = 3.09C Ra C Th C K (8) where C Ra, C Th, C K are activity concentrations of 226 Ra, 232 Th, and 40 K respectively. RESULTS Results are shown in tables 1 to 8 and in figures 3 and 4. Table 1 shows the Average Specific Activity Concentration of radionuclides while tables 2 to 8 show Calculated Radiological Hazard Indices at the Oil Spill Locations. Figures 3 and 4 show the Excess Life Time Cancer Risk and Annual Gonodal Equivalent Dose respectively. 52

4 Table 1: Average Specific Activity Concentration of Radionuclides of 226 Ra, 232 Th, and 40 K at the crude oil spilled locations. Average Value Sampled location 226 Ra 232 Th 40 K 1 Mgbede 29.30± ± ± Alu 31.03± ± ± Agbada 62.06± ± ± Iguruta 28.25± ± ± Obigbo 54.83± ± ±8.53 Control 25.84± ± ±2.49 World Standard The results of hazard indices calculation are presented in Tables 2 to 6 for the soil samples. Table 2: Calculated Hazard Indices at Mgbede Oil Spill Location Sample Code Raeq Iγ D ηgy.h -1 AEDE Hazard index Mean AGED ex in x 10-3 msvy -1 H H ELCR 1 M ± M ± M ± M ± M ± M ± Average Value ± Control ± World Standard

5 Table 3: Calculated Hazard Indices at Aluu Oil Spill Location Sample Code Raeq Iγ D ηgy.h -1 AEDE Hazard index Mean AGED x 10-3 msvy -1 H ex H in ELCR 1 AL ± AL ± AL ± AL ± AL ± AL ± Average Value ± Control ± World Standard Table 4: Calculated hazard indices at Agbada oil spill location Sample Code Raeq Iγ D ηgy.h -1 AEDE Hazard index Mean AGED ex in x 10 msvy -1 H H ELCR 1 AgI ± AgI ± AgI ± AgI ± AgI ± AgI ± Average Value ± Control ± World Standard

6 Table 5: Calculated Hazard Indices at Igwuruta Oil Spill Location Sample Code Raeq Iγ D ηgy.h -1 AEDE Hazard index Mean AGED ex in x 10 msvy -1 H H ELCR 1 Ig ± Ig ± Ig ± Ig ± Ig ± Ig ± Average Value ± Control ± World Standard Table 6: Calculated Hazard Indices at Obigbo Oil Spill Location Sample Code Raeq Iγ D ηgy.h -1 AEDE Hazard index Mean AGED ex in x 10-3 msvy -1 H H ELCR 1 Obgb ± Obgb ± Obgb ± Obgb ± Obgb ± Obgb ± Average Value ± Control ± World Standard

7 Table 7: Excess Lifetime Cancer Risk and percentage risk analysis Oil Spilled Sites Different point of the sites x10-3 Average x10-3 Control x10-3 Standard x10-3 % risk Analysis Mgbede Aluu Agbada Igwuruta Obigbo Table 8: Annual Gonadal Equivalent Dose (AGED). Oil Spilled Sites Different point of the sites Av. Contrl. Std. Mgbede Aluu Agbada Igwuruta Obigbo

8 Av. AGED (msvyr-1) ELCR (x10-1 ) Am. J. Sci. Ind. Res., 2016, 7(3): Average Control UNSCEAR 0 Mgbede Aluu Agbada Igwuruta Obigbo Oil Spilled sites Fig 3: Comparison of average excess lifetime cancer risk with control and UNCEAR, 2000 world standard Average Control UNSCEAR Mgbede Aluu Agbada Igwuruta Obigbo Oil Spilled sites Fig. 4: Comparison of Average values of AGED with the control and the UNSCEAR standard. 57

9 DISCUSSIONS The average annual gonadal equivalent dose (AGED) exceeded the recommended maximum permissible limit of 300 in all the crude oil spilled locations as shown in Table This is in agreement with the mean value of reported by Ajibode et al., (2013). At Agbada oil spill location the average AGED exceeded the world standard value by 65.58%. This shows high level of threat to sensitive cells like the gonad, bone marrow or thyroid. The radium equivalent (Ra eq ) dose ranged from to Bqkg -1 with mean value of Bqkg -1, whereas Agbalagba (2012) obtained mean value of 98.5 Bqkg -1 from similar environment. This variance may be attributed to difference in degree of perturbation. Absorbed dose values are high in comparison with 32 ngyh -1 to 59.1 ngyh -1 obtained by Senthilkumar et al., (2010) for soil sample in Thanjavur. The mean annual effective dose equivalent (AEDE) at Agbada is within the world standard limit of 1.0mSvy-1 but exceeded that obtained by Ajibode et al., (2013) in oil and gas environment of Niger Delta area. The percentage risk analysis result in Table 7 showed that the health risk from excess lifetime cancer risk is minimal at Mgbede, Aluu, Igwuruta and Obigbo but significant at Agbada. Generally the values of excess lifetime cancer risk are within normal but are at variance with the values obtained by Osimobi et al., (2012) that reported lower excess lifetime cancer risk and annual gonadal equivalent dose for non oil and gas environment of Enugu. This means that the higher excess lifetime cancer risk and higher annual gonadal equivalent dose obtained may be attributed to the oil spillage in the study areas. CONCLUSION The values of the determined radium equivalent, excess lifetime cancer risk, annual gonadal equivalent dose ranged from 87.05±3.93 to ±9.06 Bqkg -1, 0.21x10-3 to 0.39x10-3, to respectively. I-gamma index ranged from 0.57 to 1.40 Bqkg -1. The external and internal hazard indices ranged from 0.22 to 0.54, and 0.26 to 0.82 respectively. The average absorbed doses ranged from to ngyh -1. Generally, the results are within international standards of ICRP and UNSCEAR. However, they are above the control samples obtained from similar geological environment without crude oil contamination therefore the obtained values serve as baseline data. Finally, oil operating firms should be proactive in curtailing the level of environmental degradation from oil and gas exploration and exploitation. REFERENCES Agbalagba, E.O., Avwiri, G.O., and Chad-Umoren, Y.E., (2012). Gamma spectroscopy measurement of natural radioactivity and assessment of radiation hazard indices in soil samples from oil fields environment of Delta State, Nigeria. Journal of Environmental Radioactivity, 109 (2012), Ajayi, I.R. (2008). Background radioactivity in the sediment of some rivers and streams in Akoko, Southwestern, Nigeria and their radiological effects. Research Journal of Applied Science, 3 (3): Ajibode, M.O., Avwiri, G.O., and Agbalagba, E.O., (2013). Evaluation of radiation hazard indices in oil mineral lease in Delta State, Nigeria. International Journal of Engineering and Applied Science, vol. 4, No. 2. Alam, M.N., Chowdhury, M.I., Kamal, M., Ghose, S., and Ismal, M.N., (1999). The 226 Ra, 232 Th and 40 K activities in beach sand minerals and beach soil of Cox s Bazer. Bangladesh Journal of Environmental Radioactivity, 46(2): Ashraf, E.M.K, Layia, H.A., Amany, A.A., and Al-Omran, A.M., (2010). NORM in clay deposits. Proceedings of Third European IRPA Congress 2010 June, 14-18, Helsinki, Finland, 1-9. Attallah, M. F., Awwad, N. S. and Aly, H. F., (2012). Environmental radioactivity of TE-NORM waste produced from petroleum industry in Egypt: Review on characterization and treatment hot laboratories and waste management center, Atomic Energy Authority, Cairo, Egypt Diab, H.M., Nouh, S.A., Hamdy, A., and El-Fiki, S.A., (2008). Evaluation of natural radioactivity in a cultivated area around a fertilizer factory. Journal of Nuclear and Radiation Physics, 3(1) International Atomic Energy Agency, (2007). Identification of radioactive sources and devices, IAEA Nuclear Security Series No. 5, Technical Guidance Reference Manual, STI/PUB/1278, VIENNA. Osimobi, J.C., Avwiri, G.O., and Agbalagba, E.O., (2012). Evaluation of radiation health indices and excess lifetime cancer risk due to natural radioactivity in the soil profile of Udi and Ezeagu, Enugu State, Nigeria. Journal of Environmental Earth Sciences, (1) 1-10 Senthilkumar, B., Dhavamani, V., Ramkuma, S. and Philominathan, P., (2010). Measurement of gamma radiation levels in soil samples from Thanjavur, using γ- ray spectrometry and estimation of population exposure. Journal of Medical Physics, 35:

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