Evaluation of Natural Radioactivity and Radiological Health Implications Of Oniru Beach Lagos, South-Western, Nigeria

Abstract

This study assessed the activity concentrations of 226Ra, 232Th and 40K in beach sand samples of Oniru beach, south-western Nigeria and evaluated its radiological implications on human health. The samples were analysed by gamma spectrometric technique which employs a low background NaI (Tl) gamma detector. Mean specific activities of 226Ra, 232Th and 40K were 56.65±18.7, 53.11±12.7 and 603.52±188.7 Bqkg-1 respectively, which were higher than the their respective safety limits prescribed by the United Nations Scientific committee on the Effects of Atomic Radiation. Calculated mean air absorbed dose rate at 1 m above ground was 83.42 nGhh-1, with corresponding annual effective dose equivalent of 0.1 mSy-1. These values were higher than the world precautionary safety limits, which therefore identified Oniru beach as a high background radiation area that demands urgent attention. Computed results of other radiation hazard parameters complimented the claim. Excess lifetime cancer risk (ELCR) recorded an average value of 0.35× 10-3 which is above the world safety limit. This point to the likelihood of cancer incidence among the exposed population. Multivariate statistical analysis involving Pearson correlation analysis, factor analysis and cluster analysis indicated that the concentrations of 226Ra and 232Th in the studied beach sand are principally responsible for the enhanced level of natural radioactivity of Oniru beach.