Annual effective dose from 222Rn in groundwater of a Nigeria University campus area

Radon, the heaviest among the noble gases in the periodic table of element is a radioactive nuclide that is naturally available in rocks, soil and water. It has become the subject of many research efforts in recent years due to its leading role in causing cancer. In this study, a total of 68 groundwater samples were collected and assayed using alpha spectrometry with RAD7 radon detector with RAD-H 2 O accessories manufactured by Durridge CO (USA). The 222 Rn concentration measured were in the range of 0.6–36.2 Bq L −1 with an average of 13.33 Bq L −1 , 7.0–41.5 Bq L −1 with mean value 23.3 Bq L −1 and 0.6–27.4 Bq L −1 with an average value of 7.4 Bq L −1 for hand dug wells (HDW), hand pumped boreholes (HPB) and motorized boreholes (MBH), respectively. About 54, 86 and 15% of samples from the HDW, HPB and MBH, respectively, exceeded the parametric reference level of 11.1 Bq L −1 suggested by United State of America Environmental Protection Agency but lower than the permissible limit of 100 Bq L −1 by World Health Organization (WHO) and European Union. The average annual effective doses resulting from inhalation and ingestion of radon in water obtained for the three groundwater sources are less than recommended limits by WHO and ICRP. The data obtained from this study are comparable with similar studies conducted in Nigeria and other parts of the world as reported in literature. Continuous radon monitoring in drinking water and indoor environment is however recommended for the study area.