ESTIMATION OF THE EQUIVALENT AND EFFECTIVE DOSE OF RADON FROM THE INGESTION OF WATER FROM DJIRI RIVER BY THE POPULATION, BRAZZAVILLE, REPUBLIC OF CONGO
This study aimed to measure radon concentration in Djiri River water and to evaluate the associated equivalent doses, effective doses, and lifetime cancer mortality risks for the population of Brazzaville, Republic of Congo. Radon concentration was measured in 29 water samples collected from the Djiri River using an AlphaGUARD PQ2000 PRO radon detector. Polyethylene terephthalate (PET) bottles were evaluated for sample storage in order to estimate radon losses during storage. To enable a direct comparison with the National Research Council (1999) reference values, the estimated cancer mortality risks were normalized to the same reference radon concentration. Measured radon concentrations ranged from 0.23 to 0.73 Bq/L, with a mean value of 0.425±0.12 Bq/L (equivalent to 425±120 Bq/m³). These concentrations are low and indicate that radiation exposure through drinking water ingestion is minimal under the investigated conditions. The estimated annual effective doses from water ingestion were 5.37×10⁻6 mSv/year for infants, 4.45×10⁻3 mSv/year for 1-year-old children, 2.03×10⁻3 mSv/year for 5-year-old children, 1.18×10⁻3 mSv/year for 10-year-old children, 4.38×10⁻6 mSv/year for 15-year-old children, and 4.02×10⁻3 mSv/year for adults. All estimated doses remained well below the World Health Organization guideline value of 0.1 mSv/year for drinking water. The estimated lifetime cancer mortality risks for males, females, and the total population were 6.35×10⁻7, 9.45×10⁻7, and 7.68×10⁻7, respectively. After normalization to the same radon concentration, these estimates were consistent with the projections reported by the National Research Council (1999). Although the estimated doses and risks are very low and do not indicate a significant radiological health concern, the results support periodic monitoring of radon in the Djiri River as part of routine environmental and public health surveillance.