Comparative Assessment of Cobalt Bioaccessibility and Bioavailability from Contaminated Media Using Unified BARGE Method and Rat Model

Contaminated concrete (CC) was generated during the decommissioning of nuclear power plants, with the potential presence of radioactive cobalt (60Co). Inadvertent ingestion of these materials poses health risks to both humans and animals, underscoring the need to evaluate Co toxicity and exposure. This study investigated Co exposure from CC samples spiked at 10, 100, and 1000 mg/kg−1 through a tiered approach, incorporating the in vitro assay based on the Unified BARGE Method (UBM), in vivo testing in rats, and biokinetic modeling utilizing Simulation Analysis and Modeling (SAAM II). Co exhibited pH-dependent solubility, demonstrating greater bioaccessibility during the gastric phase (64.9%–77.4%) than in the gastrointestinal phase (47.0%–69.7%), due to the enhanced release of soluble Co2+ ions under acidic conditions. The in vivo relative bioavailability (RBA) of Co varied from 46% to 87% in blood and from 4% to 35% in urine, indicating significant systemic absorption, particularly at higher doses. The predictions made by SAAM II are closely aligned with the measured in vitro data, supporting the reliability of model-based extrapolation. Furthermore, significant dose-dependent interactions with Fe and Zn were observed, highlighting competitive uptake and regulatory mechanisms. This integration of in vitro, in vivo, and modeling approaches allows for more accurate assessments of human health risks associated with Co exposure to nuclear waste materials than methods based on the total concentration or single assay alone.