Natural radioactivity in groundwater system and estimates of committed effective dose due to water ingestion in Ilorin, Nigeria

Natural radioactivity measurements in drinking water have been performed in many parts of the world, mostly for assessment of the doses and risk resulting from consuming water. A study of the radionuclide concentrations in groundwater samples collected from wells distributed within Ilorin, west of central Nigeria has been carried out. Twenty Eight (28) water samples were analyzed by gamma ray spectroscopy to determine the 226Ra, 228Ra, and 40K concentrations. The specific activity values ranged from 0.02 to 7.4 Bq/l for 226Ra, 0.009 to 5.6 Bq/l for 228Ra, and 0.45 to 30.14 Bq/l for 40K. The annual ingestions of these radionuclides, using local consumption rates (average over the whole population) of 1 liter per day, were subsequently estimated to range from 0 to 0.8 mSv/y with an average of 0.36 mSv/y, 0 to 1.42 mSv/y with an average of 0.50 mSv/y, and 0 to 0.01 mSv/y with an average of 0.01 mSv/y for 226Ra, 228Ra, and 40K respectively. The results show that the mean annual effective dose values received as a result of the combined ingestion of the radionuclides from many individual wells in the study area exceed the norm of drinking water quality established by UNSCEAR/WHO. Efforts should therefore be made by policy makers to protect the populace from long-term health consequences. (authors)