Hakai Magazine

A MRI being performed on a patient
Gadolinium is used to enhance contrast in magnetic resonance imaging (MRI), but it may also be an overlooked source of environmental pollution. Photo by ONOKY-Photononstop/Alamy Stock Photo

Is a Chemical Used in MRIs a Threat to Marine Ecosystems?

Gadolinium, a rare earth element important for medical testing, has found its way into coastal waters.

Authored by

by Joshua Rapp Learn

Article body copy

A rare earth element critical to the diagnosis of medical conditions is accumulating in the world’s oceans—and no one knows exactly how, and if, it will affect the marine ecosystem.

Nearly half a billion doses of the element gadolinium have been given to patients worldwide to date. Patients are injected with gadolinium-based agents before certain magnetic resonance imaging (MRI) examinations. Most passes through the body and is urinated out, eventually entering the ocean through wastewater or getting back into freshwater reservoirs, according to Emanuel Kanal, a professor of radiology and neuroradiology at the University of Pittsburgh Medical Center in Pennsylvania. The element was detected in the North Sea off Germany in the 1990s, and it has since been documented in the rivers and waters of countries such as Australia, Japan, France, and the United States.

A new review published by researchers in Poland shows that gadolinium released into the marine environment affects many creatures, although how an animal reacts to the element varies. Experiments have shown that Cnidaria (including jellyfish) and microscopic rotifers (tiny plankton) are more sensitive than crustaceans to rare earth elements like gadolinium, which can be toxic to certain species of algae.

Ewa Olkowska, a researcher in environmental toxicology at the Medical University of Gdańsk and coauthor of the review, says the health effects of gadolinium on marine life and humans are not well understood, including how it might negatively interact with other pollutants.

“We don’t put only one pollutant into [the] marine [environment]. We put a lot of different compounds. [So] this is the big issue,” Olkowska says, adding that such research is very complex and time-consuming, but further investment into the issue is necessary to determine potential problems.

It’s also possible that these chemicals can boomerang back to humans through the food chain. The review notes that aquatic animals or plants could absorb gadolinium from the water, and even terrestrial crops could be affected if irrigated by gadolinium-polluted water.

Filtering the element through water treatment facilities is possible. Boulder, Colorado upgraded its wastewater plant in 2008 with technology that successfully removed gadolinium along with other compounds known as endocrine disruptors that affect fish. (A study on the plant found that fish swimming in post-upgrade water were healthier.) Other research notes that a reverse osmosis membrane can achieve a nearly 100 percent reduction in gadolinium.

More widespread screening of the element has yet to be adopted in wastewater treatment facilities, partly because gadolinium pollution is still an emerging issue and governments have no laws requiring its removal. Meanwhile the rare earth element continues to accumulate in marine ecosystems—the review notes that studies have found gadolinium in a number of rivers, canals, and surface water bodies, and in the ocean, with some of the largest concentrations detected off the Kona Coast of Hawai‘i.

Kanal, who was not involved in Olkowska’s review, says that at this time scientists do not know the ecosystem health effects, if any, of this environmental increase in gadolinium. But the material is accumulating in water systems near large population centers where more MRIs are happening.

“There’s so much here that we don’t know,” Kanal says. “It’s easy to panic, and it’s easy to ignore, but I’m not sure that either panicking or ignoring are warranted or appropriate.”