Gadolinium (Gd) contamination from anthropogenic sources, particularly MRI, is higher in tap water in large EU cities than in tap water from Asian or American megacities, according to findings from a study scheduled for publication in Chemosphere’s February 2026 issue.
Using a technique that builds on a previously validated method, a French team headed by geochemist Jean-Alix Barrat, Institut Universitaire Européen de la Mer (IUEM), Université Brest, sought to analyze and compare the levels of anthropogenic Gd in big-city tap water systems.
With MRI use increasing, Gd contamination of drinking-water distribution systems is a significant problem. Wastewater treatment plants do not effectively treat gadolinium-based contrast agents (GBCAs) excreted by patients; thus, the GBCAs end up in surface freshwater bodies, such as rivers, and ultimately accumulate in coastal marine ecosystems. The effect of low but steady levels of these contaminants on ecosystems, and on human health when delivered through city water systems, has yet to be fully determined or quantified.
Barrat’s team used a method based on the coprecipitation of rare earth elements (REEs) with iron hydroxides and yttrium (REY) after adding a thulium (Tm) “spike” to estimate the amount of macrocyclic GBCAs in tap water samples. They analyzed samples from different cities in Europe (including Berlin, Amsterdam, Paris, and Lyon) and on other continents (e.g., Los Angeles, New York, and Rio de Janeiro in the Americas; Beijing, Guangzhou, Wuhan, Shanghai, Seoul, and Tokyo in Asia), using river water samples for comparison.
Selected REY patterns of tap water normalized to Post-Archean Australian Shale (PAAS).Barrat et al and Chemosphere
The authors wrote that distinguishing the proportion of anthropogenic Gd can be readily estimated using REE patterns in water-quality and environmental studies.
Additionally, they noted that the sources of water used for tap water production vary and may include river water, groundwater, or seawater; these water sources have different initial REY concentrations. Furthermore, different neighborhoods in the same city may have different sources for their water supply.
While the purification processes used in different cities can vary significantly, which may alter the concentrations of trace elements in tap water, the authors wrote that they were able to qualitatively assess the effect of the entire purification process on REY abundances in some of the tap water samples.
In their analysis, the levels of Gd contamination in European cities were consistently high, with water-contamination levels higher than 4 ng/kg for 23 out of 43 samples; values higher than 60 ng/kg were present in Berlin and Amsterdam.
Outside of the EU, only three cities -- Tunis, Rio de Janeiro, and Washington, DC -- of the 20 sampled had levels exceeding 4 ng/kg. The authors noted that city size was not correlated with these rates: They analyzed samples drawn from cities with the highest global populations, including Shanghai (28 million), Tokyo (37 million), Seoul (25 million), New York City (20 million), and Los Angeles (18 million).
Anthropogenic Gd for the tap water samples analyzed in this work.Barratt et al and Chemosphere
They concluded that not only was the disparity in contamination levels not driven by population numbers but it was also not dependent on the number of MRI facilities present.
One contributing factor is the water source, the authors explained.
“Contamination in tap water depends primarily on the choice of resources used to produce it, and therefore on the level of exposure of that resource to effluents containing Gd. This is clearly illustrated by certain large European cities such as Amsterdam, Paris, and London, where tap water is mainly produced from river water known to be moderately to highly contaminated with Gd. Conversely and obviously, certain cities such as Stanford and Kiel, which use resources that are little or not at all contaminated, have tap water that is free of anthropogenic Gd,” the French team wrote.
A second factor, they added, is that differences in water-treatment processes may lead to variations in the behavior and degradation of GBCAs, which they add could explain the markedly low concentrations of anthropogenic Gd in Asian cities in particular.
The authors noted that both anthropogenic Gd amounts and macrocyclic GBCAs are either undetectable or present in very low amounts in samples from Wuhan, Guangzhou, and even Shanghai: “We do not know which GBCAs are injected in China, but it would be surprising if linear GBCAs were still widely used in this country. If this is not the case, the absence or rarity of macrocyclic GBCAs would imply that they have been very effectively degraded during water purification.”
They reiterated that there is a compelling need for more research on the behavior of REYs and GBCAs with water purification methods. Moreover, the findings raise questions about not just wastewater treatment, medical practices, and water resource conservation for the EU in particular.
Read the detailed findings of the study here.
