17 Metalle gehören zu den Seltenen Erden.Bild: Ullstein Bild/Getty Images
Rare earth elements, essential components in modern technology, are increasingly being detected in waterways and potentially impacting aquatic life.
February 12, 2026, 10:42 PMFebruary 12, 2026, 10:42 PM
Rare earth elements are integral to a wide range of modern technologies, including smartphones, displays, electric motors, LED lighting, wind turbines, and medical contrast agents. While these 17 metals with similar chemical properties are found throughout the Earth’s crust, geological and economic factors limit viable extraction in many locations. Extraction in countries with less stringent regulations, such as China, is often linked to environmental concerns.
A recent study by the Swiss Federal Institute of Aquatic Science and Technology (Eawag) reveals that the presence of these rare earth elements is creating problems in local waterways. Researchers analyzed 41 sites in rivers and streams, as well as the effluent from 60 wastewater treatment plants in the Canton of Zurich, for traces of these metals.
The results, published in the journal “Aqua & Gas,” show that three rare earth elements are present at elevated levels. Gadolinium was found in particularly high concentrations in treated wastewater, and also in flowing waters. Lanthanum and cerium also showed unusually high values in the effluent of individual wastewater treatment plants.
Gadolinium is a contrast agent used in magnetic resonance imaging (MRI) in medicine, entering wastewater through patients’ urine. The study demonstrates the widespread extent of this contamination.
Contamination from Medical Contrast Agents in Urine
Due to its chemical structure, gadolinium is poorly retained by wastewater treatment plants and therefore enters waterways. The investigation indicates that these measured concentrations could have long-term negative effects on aquatic organisms.
Lanthanum and cerium are used in wastewater treatment plants as so-called precipitating agents to remove phosphorus. Risk assessments suggest that the locally remarkably high concentrations likely have negative effects on aquatic organisms, though sufficient ecotoxicological data for a definitive assessment were not available.
While measurements were taken only in the Canton of Zurich, study leader Ralf Kägi of Eawag said the findings can be extrapolated to Switzerland with some limitations. The amount of gadolinium entering the water depends heavily on the catchment area of the wastewater treatment plants. “The more hospitals, the higher the metal inputs. In the Engadine region, I would therefore expect lower, human-induced concentrations,” said the Eawag researcher.
Because rare earth elements occur naturally in the Earth’s crust, there is also a natural concentration in waterways. The study therefore investigated the proportion of human-made traces of rare earth elements. “Three of the 17 rare earth elements were clearly of anthropogenic origin. For all other metals, we found a natural background,” Kägi said.
Collecting Urine from MRI Patients
To address the gadolinium contamination, researchers suggest reducing inputs at the source. This could involve collecting the urine of patients immediately after MRI examinations in special bags and disposing of it with the waste. The urine can be converted into a solid gel with a granular substance in the bag, which can then be disposed of and incinerated.
The use of precipitating agents based on lanthanum and cerium is not currently recommended, the authors write, at least until the environmental impacts are fully clarified.
A rare earth mine in Brazil. The South American country has the second-largest reserves after China.Bild: keystone
