European fluxes of medical gadolinium to the ocean: A model based on healthcare databases.

Marine ecosystems are exposed to a multitude of stresses, including emerging metals as Rare Earth Elements. The management of these emerging contaminants represents a significant environmental issue. For the past three decades, the increasing medical use of gadolinium-based contrast agents (GBCAs) has contributed to their widespread dispersion in hydrosystems, raising concerns for ocean conservation. In order to control GBCA contamination pathways, a better understanding of the cycle of these elements is needed, based on the reliable characterization of fluxes from watersheds. Our study proposes an unprecedented annual flux model for anthropogenic gadolinium (Gd) based on GBCA consumption, demographics and medical uses. This model enabled the mapping of Gd fluxes for 48 European countries. The results show that 43 % of Gd is exported to the Atlantic Ocean, 24 % to the Black Sea, 23 % to the Mediterranean Sea and 9 % to the Baltic Sea. Together, Germany, France and Italy contribute 40 % of Europe's annual flux. Our study was therefore able to identify the current and future major contributors to Gd flux in Europe and identify abrupt changes related to the COVID-19 pandemic.