Biokinetic modelling of uranium retention and committed organ doses from groundwater ingestion in Chengalpattu District, Tamil Nadu, India

Groundwater samples collected from Chengalpattu District were analyzed for uranium using an LED fluorimeter. The measured values ranged between 0.02 μg L −1 and 2.814 μg L −1 , with an average concentration of 0.347 μg L −1 . All measured values were within the permissible limits recommended by the World Health Organization and the International Commission on Radiological Protection. The study evaluated organ-specific uranium retention and committed equivalent doses for adults under chronic ingestion conditions using a hair-based compartmental biokinetic model. The results further confirm the previously reported non-uniform distribution of uranium among human organs and tissues, with tissue-specific retention characteristics governing its accumulation and residence time. Skeletal tissues, particularly cortical and trabecular bone volumes, exhibited the highest accumulation due to the strong affinity of uranyl ions for phosphate groups in hydroxyapatite, leading to prolonged retention and the largest contribution to internal radiation dose. In contrast, soft tissues, gastrointestinal tract segments, kidneys, and liver showed lower retention due to faster transfer and elimination rates. The gastrointestinal tract acts as the primary entry pathway, while the kidneys and urinary bladder play key roles in uranium clearance. Excretion analysis indicates that faeces elimination is the dominant pathway, followed by urinary and minor hair excretion. The highest committed equivalent doses were observed in bone surfaces, followed by other soft tissues, the lower large intestine wall, kidneys, upper large intestine wall, small intestine wall, stomach wall, and liver. The overall effective dose is mainly influenced by skeletal retention; however, the estimated doses across all locations remain low and well within international safety limits. These findings suggest minimal radiological health risk from chronic uranium ingestion in the study area and demonstrate that the hair compartmental biokinetic model is a reliable tool for long-term exposure and risk assessment.