Rare earth element abundances and gadolinium contamination in tap water worldwide

Gadolinium-based contrast agents (GBCAs) are widely used in magnetic resonance imaging (MRI) and have emerged as persistent contaminants in surface and drinking water since the 1990s. We present a method based on the coprecipitation of rare earth elements (REEs) with iron hydroxides to estimate the amount of macrocyclic GBCAs in water, and apply it here for the first time to investigate the degree of Gd contamination in tap water worldwide. Our results indicate that Gd contamination is widespread in drinking water distribution systems. Tap water in big European cities such as Berlin, Amsterdam, Paris, and Lyon is more contaminated in Gd than tap water from Asian (Beijing, Guangzhou, Wuhan, Shanghai, Seoul, Tokyo) or American megacities (Los Angeles, New York, and Rio de Janeiro). Furthermore, our data suggest that drinking water treatment processes degrade Gd complexes to varying extent, which can increase the bioavailability of free Gd ions.