Quantification and Evaluation of Radon-222 in Groundwater of Flood-Affected Areas in Borno State, North-Eastern Nigeria: Implications for Lung Cancer Risk

Abstract

Radon-222 (²²²Rn), a naturally occurring radioactive gas, which is soluble in water may damage internal organs if ingested or inhaled. This study investigated the concentration of ²²²Rn in groundwater of 28 locations across five flood-affected areas of Borno state, in September 2024. Groundwater samples were collected and analyzed using a Tri-Carb-LSA 1000 Liquid Scintillation Counter. Elevated levels of ²²²Rn were recorded in Jere (12.35 Bq/L), Konduga (11.33 Bq/L), and Magumeri (10.81 Bq/L). The concentrations in Konduga and Jere exceed the U.S. Environmental Protection Agency maximum contaminant level of 11.1 Bq/L. The total (ingestion and inhalation) annual effective doses varied by age and sex and ranged between 6.57 and 69.49 µSv/y for males, and between 2.01 and 64.52 µSv/y for females. Stomach received the highest absorbed doses (4.83–57.20 µSv/y), consistent with its role as the primary reservoir for ingested water. Lungs also received non-negligible doses of up to 12.11 µSv/y through systemic circulation. Over 95% of the total internal organ dose was attributable to alpha radiation, known for its high linear energy transfer and potential to cause cellular damage. This underscores a significant risk of gastrointestinal cancers and compounds the lung cancer risk. Adults had higher dose burdens than children due to larger water intake volumes. Males exhibited slightly elevated organ doses compared to females, likely due to physiological and metabolic differences. The findings emphasize the need for targeted public health interventions, including regular radon monitoring, awareness creation, and the introduction of point-of-use water treatment systems to mitigate exposur