RADIOMETRIC ASSAY OF HAZARD INDICES AND EXCESS LIFETIME CANCER RISK DUE TO NATURAL RADIOACTIVITY IN SOIL PROFILE IN OGBA/ EGBEMA/ NDONI LOCAL GOVERNMENT AREA OF RIVERS STATE, NIGERIA

Naturally occurring radio nuclides (226Ra, 232Th and 40K) were measured in soil samples collected from twelve oil fields and their host communities in Ogba/Egbema/Ndoni Local Government Area (ONELGA) of Rivers State using gamma spectroscopy. The mean activity concentration of 226Ra, 232Th and 40K in soil samples from the oil fields is 29.61± 3.03, 17.41± 1.64 and 262.63± 9.73 Bqkg-1 respectively and 19.11± 2.35, 21.26±1.41 and 224.26±11.75 Bqkg-1respectively for samples from host communities. The hazard indices and excess lifetime cancer risk were estimated using standard analytical method with mean values obtained for annual gonadal equivalent dose, annual effective dose equivalent (outdoor and indoor), hazard index (external and internal), excess lifetime cancer risk, and representative gamma index which were respectively 218.49 mSvyr-1, 39.45?Svyr-1, 157.81?Svyr-1, 0.18, 0.232, 0.138 x 10-3 and 0.49 for the host community and, 246.73 mSvyr-1, 43.47?Svyr-1, 173.9 ?Svyr-1, 0.202, 0.282, 0.152 x 10-3 and 0.547 for oilfield soil samples. The values when compared with their corresponding world permissible values were found to be below the standard limit for such environment. The soil from the study area provided no excessive exposure for the inhabitants and can be used as building material without posing any radiological threat or harm to the public users.