EVALUATION OF NATURAL RADIONUCLIDE CONTENT IN SURFACE AND GROUND WATER AND EXCESS LIFETIME CANCER RISK DUE TO GAMMA RADIOACTIVITY

The objective of this study is to evaluate the radionuclide content of the surface and ground water around oilfields and their host communities and finally assess the excess lifetime cancer risk associated with them. A total of thirty-six water samples were each taken from Tap water, Well Water and River Water in and around twelve oilfields and their host communities of Ogba, Egbema and Ndoni Local Government Area of Rivers State, Nigeria. The radionuclide concentrations in all water samples were measured using gamma spectroscopy method. The average values of 226Ra, 228Ra and 40K obtained is 9.22±0.82, 8.46±0.61 and 44.27±2.34Bq/l respectively for well water, 4.20±0.12, 4.44±0.14 and 37.85±2.15Bq/l respectively for Tap water and 6.57±0.24, 6.88±0.36 and 29.48±1.98Bq/l respectively for river water. The committed effective dose and excess lifetime cancer risk was calculated for four age brackets. The average committed effective dose for adults that take tap, well and river water ranged from 1.61 to 3.44mSv/yr and that for teenagers, children and babies ranged from 6.03 to 11.76, 8.97 to 19.09 and 10.63 to 14.73mSv/yr respectively. The excess lifetime cancer risk in adult that drank tap, well and river water ranged from 11.50 x 10-3 to 16.26 x 10-3. And that for teenagers, children and babies ranged from 21.24 to 41.16 x 10-3, 31.42 to 66.83 x 10-3 and 25.53 to 51.57 x 10-3 respectively. These results when compared with their corresponding world permissible values were found to be above the standard limit for such environment and as such long term radiation exposure to workers and residents of the study areas could pose health threat.