A Global Imprint of Gadolinium-Based Contrast Agents Used in Magnetic Resonance Imaging in Drinking Water

Since the 1980s, rare earth elements (REE), particularly gadolinium (Gd) used in gadolinium-based contrast agents (GdCA), have revolutionized Magnetic Resonance Imaging (MRI) diagnostics. However, the near-complete persistence of these compounds through wastewater treatment processes has led to widespread global environmental contamination. Here, we present a global assessment of REE concentrations and GdCA signatures in tap water from 148 cities across 89 countries and Antarctica, where anthropogenic Gd ranges from 0.1 to 61.2 ng L^-1 and accounts for up to 99% of total dissolved Gd. Contamination hotspots are concentrated in Europe and North America. While Gd levels scale with MRI usage and wastewater generation, the primary driver on contamination exposure is the local drinking water source. These results reveal Gd as a sensitive global tracer of wastewater influence on drinking-water systems. Although current concentrations pose limited immediate health risks, their worldwide prevalence highlights the emerging threat of pharmaceutical pollution and the need for rapid advances in wastewater treatment, environmental monitoring, and water-resource management.