• Posted December 11, 2025

Medical Imaging Contributing To Water Pollution, Experts Say

Contrast chemicals injected into people for medical imaging scans are likely contributing to water pollution, a new study says.

Medicare patients alone received 13.5 billion milliliters of contrast media between 2011 and 2024, and those chemicals wound up in waterways after people excreted them, researchers recently reported in JAMA Network Open.

“Contrast agents are necessary for effective imaging, but they don’t disappear after use,” said lead researcher Dr. Florence Doo, an assistant professor at the University of Maryland Medical Intelligent Imaging Center in Baltimore.

“Iodine and gadolinium are non-renewable resources that can enter wastewater and accumulate in rivers, oceans and even drinking water,” Doo said in a news release.

People undergoing X-ray or CT scans are sometimes given iodine or barium-sulfate compounds that cause certain tissues, blood vessels or organs to light up, allowing radiologists a better look at potential health problems.

For MRI scans, radiologists use gadolinium, a substance that alters the magnetic properties of water molecules in the human body.

These are critical for diagnosing disease, but they are also persistent pollutants, researchers said in background notes. They aren’t biodegradable, and conventional wastewater treatment doesn’t fully remove them.

For the new study, researchers analyzed 169 million contrast-enhanced imaging procedures that Medicare covered over 13 years.

Iodine-based contrast agents accounted for more than 95% of the total volume, or nearly 12.9 billion milliliters. Of those, agents used in CT scans of the abdomen and pelvis alone contributed 4.4 billion milliliters.

Gadolinium agents were less frequently used, but still contributed nearly 600 million milliliters, researchers said. Brain MRIs were the most common scan using these contrast materials.

Overall, just a handful of procedures accounted for 80% of all contrast use, researchers concluded.

“Our study shows that a small number of imaging procedures drive the majority of contrast use. Focusing on those highest-use imaging types make meaningful changes tractable and could significantly reduce health care’s environmental footprint,” researcher Elizabeth Rula, executive director of the Harvey L. Neiman Health Policy Institute in Reston, Va., said in a news release.

Doctors can help by making sure their imaging orders are necessary, while radiologists can lower the doses of contrast agents by basing them on a patient’s weight, researchers said.

Biodegradable contrast media are under development, researchers noted. Another solution could involve AI, which might be able to accurately analyze medical imaging scans even if less contrast media is used.

“We can’t ignore the environmental consequences of medical imaging,” Doo said. “Stewardship of contrast agents is a measurable and impactful way to align patient care with planetary health and should be an important part of broader health care sustainability efforts.”

More information

The Radiological Society of North America has more on contrast materials for medical imaging.

SOURCES: Harvey L. Neiman Health Policy Institute, news release, Dec. 4, 2025; JAMA Network Open, Dec. 5, 2025