Executive Summary

Zurich waters are heavily contaminated with gadolinium – a metal used in MRI contrast agents. The water research institute Eawag has measured concentrations up to one thousand times higher than natural values. Treatment plants cannot filter the substance. As a solution, a pilot project in Graubünden is being tested: patients should use urine collection bags 24 hours after the examination to retain the gadolinium directly.

People

Topics

  • Medical environmental contamination
  • Water quality and ecosystem protection
  • Treatment technology and wastewater processing

Clarus Lead

Hospital wastewater endangers Zurich waters: The water research institute Eawag has documented that gadolinium – a contrast agent used in MRI examinations – is landing in Zurich lakes and rivers in extreme concentrations. Ralf Kägi from Eawag warns: the ecosystem of individual waterways is already endangered, although the exact toxicological effects have not yet been fully researched. A simple intervention could solve the problem – but implementation so far has failed due to organizational hurdles.

Detailed Summary

The concentration of gadolinium in Zurich waters exceeds natural background values by up to one thousand times. The metal enters treatment plants through patient urine and is not retained there – it flows almost unimpeded into surface waters.

The background is medically sound: During MRI examinations, gadolinium is injected as a contrast agent. The body excretes it through urine. However, treatment plants are not designed to filter gadolinium. Edith Thourish from the Water Protection office of Canton Zurich confirms: the technology for this simply does not exist in existing facilities.

The pilot project in Graubünden therefore tests a preventive solution: patients should wear a urine collection bag 24 hours after the MRI. The contaminated secretion is disposed of directly – the gadolinium never reaches the treatment plants. Edith Thourish considers this method "probably the best" available option. However, outstanding questions are still blocking its introduction in Zurich. Zurich City Hospital "is following the discussion" but has not yet implemented the system.

Key Findings

  • Gadolinium concentrations in Zurich waters are up to 1,000 times higher than natural values
  • The metal comes from MRI contrast agents, which cannot be filtered out at treatment plants
  • A urine collection bag system (24 hours post-MRI) could solve the problem at the source
  • Graubünden is testing the model; Zurich is still awaiting clarification

Critical Questions

  1. Evidence/Data Quality: How many measurements has Eawag conducted, and over what time period? Are there regional differences in gadolinium contamination, and are all treatment plants equally affected?

  2. Evidence/Source Validity: Which international studies have already documented similar contamination in other countries? Do the findings differ, and if so, why?

  3. Conflicts of Interest/Incentives: Who bears the cost of the urine collection bags – patient, hospital, or health insurance? Could financial barriers endanger compliance?

  4. Causality/Alternatives: Are only MRI contrast agents responsible, or do other medical or industrial sources also contribute to gadolinium emissions? What alternative contrast agents exist?

  5. Feasibility/Risks: Why is implementation delayed in Zurich despite a known solution? What "clarifications" are still necessary, and how long will that take?

  6. Feasibility/Side Effects: How is patient compliance ensured? Are patients informed about the environmental impacts of their MRI?

  7. Causality/Counter-Hypotheses: Could Eawag rule out that other factors (industrial discharges, old deposits) contribute to gadolinium contamination?

  8. Evidence/Data Quality: What toxicological threshold values apply for gadolinium in aquatic ecosystems, and are they being exceeded?

References

Primary Source: Regionaljournal Zurich-Schaffhausen – SRF Audio (23.02.2026) https://download-media.srf.ch/world/audio/Regionaljournal_Zuerich_Schaffhausen_radio/2026/02/Regionaljournal_Zuerich_Schaffhausen_radio_AUDI20260223_NR_0120_e3c896d4ba264352ac3b88eb63f0f97f.mp3

Verification Status: ✓ 23.02.2026

This text was created with the support of an AI model. Editorial responsibility: clarus.news | Fact-check: 23.02.2026