Evaluation of Background Ionizing Radiation (BIR) Due to Oil Spills Activities in Some Select Communities in Bayelsa State, Southern Nigeria

Abstract

Measurements of background ionizing radiation (BIR) in six select communities and one oil spill site in Bayelsa State, Southern Nigeria were carried out to assess the BIR status of these communities in order to quantify the radiological health risk posed to residents. Direct measurements of radiation were employed using a well-calibrated Geodetic Positioning System (etrex 10 Garmin) and a Digilert Nuclear Radiation Monitor. Results obtained from averaging the exposure rates across the six communities and one oil spill site (1 - 7) in this order Elebele (1), Emeyal 1 (2), Emeyal 2 (3), Imiringi (4), Otuasega (5), Oruma (6) and the oil spill site (Tie-Inn manifold at Kolo-Creek) (7) revealed 0.008 mRh^-1, 0.009 mRh^-1, 0.009 mRh^-1, 0.008 mRh^-1, 0.008 mRh^-1, 0.007 mRh^-1 and 0.10 mRh^-1 correspondingly. These results, when juxtaposed with the International Commission on Radiological Protection (ICRP) value, were lower compared with the accepted magnitude of 0.013 mRh^-1.  Also, the mean absorbed dose rates from the study areas (Communities and oil spill site 1 - 7) as estimated were 70.47 nGyh^-1, 76.56 nGyh^-1, 74.82 nGyh^-1, 68.7 nGyh^-1, 68.73 nGyh^-1, 63.51 nGyh^-1 and 90.48 nGyh^-1, correspondingly where 90.48 nGyh^-1 was a bit above the ICRP limit with 1.16 nGyh^-1. Computed values of Annual Effective Dose Equivalence (AEDE) for outdoor exposure at areas 1 -7 were 0.11 mSvy^-1, 0.12 mSvy^-1, 0.11 mSvy^-1, 0.10 mSvy^-1, 0.11 mSvy^-1, 0.10 mSvy^-1 and 0.14 mSvy^-1 in that order. The mean excess lifetime cancer risk (ELCR) calculated and obtained from the following areas Elebele, Emeyal 1, Emeyal 2, Imiringi, Otuasega, Oruma and oil spill site gave 0.27 x 10^-3 mSvy^-1, 0.29 x 10^-3  mSvy^-1, 0.29 x 10^-3 mSvy^-1, 0.26 x 10^-3  mSvy^-1, 0.26 mSvy^-1, 0.24 x 10^-3 mSvy^-1and 0.35 x10^-3 mSvy^-1respectively. However, ELCR measured at Emeyal 1and 2 were exactly the same as the ICRP value, unlike the oil spill site, which value exceeded the recommended value of 0.29x10^-3 mSvy^-1. The obtained values for BIR in all the study areas were lower than acceptable limit given by ICRP whereas the absorbed dose computed were below the recommended rate except at the Tie-Inn manifold, which was higher. The average AEDE calculated in the entire area were within the safe limit. However, the ELCR as estimated were below ICRP benchmark of 0.29x10^-3 mSvy^-1 in 4 areas and exactly the same value at 2 locations, while the limit was exceeded at the Tie-Inn manifold near Kolo-Creek. The ELCR result showed that BIR in the three locations was capable of causing radiological health risks to the residents in the near future owing to petroleum activities in the areas.