Evaluation of Excess Lifetime Cancer Risk from Gamma Dose Rates in Coastal Areas of Bonny Island, Rivers State, Nigeria

The study assesses the excess lifetime cancer risk from gamma dose rates measured in coastal areas of Bonny Island, Rivers state, Nigeria. An in-situ measurement of radiation exposure rate was done using well calibrated radiation meter (Digilert-100). The exposure rate ranges between 12.0 and 18.6 µRh-1 with an arithmetic mean of 14.47 µRh-1 . The absorbed dose rates ranges between 86.6 and 161.8 nGyh-1 with an arithmetic mean value of 137.5 nGyh-1. This value is higher than the population weighted world average value of 60.0 nGyh-1. Inhabitant of Bonny Island are subjected to an external effective dose ranging between 133.22 to 248.04 µSvy-1 with an arithmetic mean value of 192.93 µSvy-1. The excess lifetime cancer risk estimated from the effective dose ranges from 0.47 x 10-3 to 0.87 x 10-3with an arithmetic mean of 0.67× 10-3. The background radiation of Bonny Island has been enhanced due to oil and gas exploitation activities in the area. Keywords: Radioactive materials, excess lifetime cancer risk, gamma dose rate, Bonny, Digilert-100