Background Gamma Radiation in Nigerian Market Environment

Human exposure to ionizing radiation from natural sources is an unending and unpreventable phenomenon on earth. Radiation profile and exposure risks for some major markets in Port Harcourt metropolis have been ascertained using radiation exposure rate meter (Radalert-100). The exposure rate measured at mile 3 market and its environs ranged from 0.001±0.0001 to 0.022±0.003 mRh-1 with mean value of 0.014±0.002 mRh-1 while that measured at mile 1 ranged from 0.011±0.001 to 0.018±0.003 mRh-1 with mean value of 0.014±0.002 mRh-1. The exposure rate measured at Rumu-Okoro market ranged from 0.010±0.0001 to 0.018±0.003 mRh-1. The exposure rates measured at the three markets are relatively equal but slightly higher than the recommended safe value of 0.013 mRh-1. The mean absorbed doses estimated from the exposure rates for Mile 3, Mile 1 and Rumu-Okoro are 119.2, 113.68 and 114.8 nGyh-1 respectively, while their mean equivalent doses are 1.15, 1.19 and 1.11 mSvy-1 respectively. The annual effective dose calculated gave mean values of 0.14, 0.16 and 0.168 mSvy-1. These values are lower than the stipulated safe value of 1.0 mSvy-1. The excess lifetime cancer risk estimated exceeded the recommended values in all the sampling points. From the radiation profile of the sampled markets, no immediate radiation risk is expected though there could be a long term effects on the sellers in those markets.