Age-dependent health risks assessment due to 222Rn in drinking water depending on lithology and volcanic faults.

This study assessed the health risks associated to radon (222Rn) in different drinking water sources and soil gas at Kribi. Measurement was performed using a RAD7 for drinking water yielding concentrations from 0.07 to 11.42 Bq/L with a geometric mean of 0.81 Bq/L. Almost all radon values in water were below the reference values of 11.1 Bq/L given by Environmental Protection Agency (EPA) and 100 Bq/L by World Health Organization (WHO). For the radon in soil gas, the risk range from low to moderate according to Swedish standards. Annual effective doses resulting from ingestion for infants, children, and adults are 10.19, 4.35, and 3.10 µSv, respectively. Furthermore, the annual effective doses resulting from inhalation for infants, children, and adults are 7.48, 7.03, and 6.42 µSv, respectively. These dose values from ingestion and inhalation remain below the WHO reference limits, which are 100 µSv for adults and 200 µSv for children. Test of variation study between radon concentrations contained in water across lithological units versus water source types (p > 0.05) revealed no significant difference, indicating that lithological setting and water source type does influence the radon concentrations in the study area. It was observed that locations near the Kribi volcanic fault exhibited high concentrations. However, it was found that other locations near this same fault exhibited low concentrations. This observation suggests the existence of other local factors influencing the concentration of the elements in question, and not solely the proximity to the volcanic fault. However, the results of the study indicate a strong correlation between radon in water and radon in soil gas. This correlation, with a coefficient of r = 0.78 (p < 0.001), suggests the existence of a common geogenic source. This result highlights the influence of environmental characteristics on radon diffusion. These data thus provide a relevant reference for tropical coastal aquifers.