A new study published in JAMA Network Open has quantified the environmental footprint of contrast agents used in medical imaging, reporting that Medicare patients alone received 13.5 billion milliliters of contrast media between 2011 and 2024.

The analysis, led by researchers from the University of Maryland, Oxford University, Imperial College London, NYU Langone, and the Harvey L. Neiman Health Policy Institute, examined Medicare claims data over a 13-year span. It found that iodinated contrast agents, primarily used in CT and CTA scans, accounted for 95% of the total volume, with abdomen and pelvis CT scans alone responsible for 4.4 billion milliliters. Gadolinium-based agents, typically used in MR procedures, made up the remaining 600 million milliliters, with brain imaging being the largest contributor.

The study also noted that a small number of imaging procedures accounted for 80% of all contrast use, pointing to potential focus areas for environmental and clinical stewardship.
“Contrast agents are necessary for effective imaging, but they don’t disappear after use,” said lead author Dr. Florence Doo, director of innovation at the University of Maryland Medical Intelligent Imaging Center. “Iodine and gadolinium are nonrenewable resources that can enter wastewater and accumulate in rivers, oceans, and even drinking water.”

Conventional wastewater treatment does not effectively remove contrast media, raising concerns about the long-term impact on aquatic ecosystems and human health. The authors recommend a set of mitigation strategies, including weight-based dosing, use of multiuse vial systems, recycling programs, and prioritizing clinically appropriate imaging orders. They also note emerging alternatives such as biodegradable contrast agents and AI-based imaging technologies that may reduce the need for contrast altogether.

“Our study shows that a small number of imaging procedures drive the majority of contrast use,” said coauthor Dr. Elizabeth Rula, executive director of the Neiman Health Policy Institute. “Focusing on those highest-use imaging types makes meaningful changes tractable and could significantly reduce health care’s environmental footprint.”

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