Evidence of high bioaccessibility of gadolinium-contrast agents in natural waters after human oral uptake.

Considering the large occurrence of anthropogenic Gd concentrations in natural waters, its continuous usage increase in technology developments and products and the lack of data on potential Gd human exposure due to ingestion of contaminated waters, it is urgently needed to understand how gadolinium contrast agents (Gd-CAs) reacts in the human digestive system. Here, we aimed to identify through in vitro bioaccessibility tests whether Gd-CAs can be potentially assimilated by humans after oral uptake and if there is a significant difference between contrast agents. We also roughly estimated the potential bioaccessibility of anthropogenic Gd for tap waters worldwide. Gd-CAs are highly bioaccessible (77 to 112%). The macrocyclic complexes pose the highest potential risk, because there are more stable than linear complexes in the gastrointestinal tract and, as such, tend to remain in solution and thus might bring Gd at the intestinal barrier making it potentially bioavailable. The estimated range of potential intake of Gd varied from 13 to 4839 μg in a lifespan of 70 years. The high bioaccessibility of anthropogenic Gd in tap waters calls for appropriate actions to develop better practices to treat wastewater contaminated by Gd-CAs in order to safeguard population and ecosystem health.