MRI use flushes gadolinium into San Francisco Bay

The levels of gadolinium in the San Francisco Bay have been steadily increasing over the past two decades, according to a study recently published in Environmental Science & Technology. Gadolinium is a rare-earth metal and the potential long-term effects of its exposure have not been studied in detail.

Russell Flegal, PhD, and his research team at UC Santa Cruz collected and analyzed water samples throughout the San Francisco Bay from 1993 to 2013, as part of the San Francisco Bay Regional Monitoring Program.

They found the gadolinium levels to be much higher in the southern end of the Bay, which is home to about 5 million people and densely populated with medical and industrial facilities, than in the central and northern regions. They also observed a sevenfold rise in gadolinium concentration in the South Bay over that time period.

The study attributes the rising level of gadolinium contamination largely to the growing number of magnetic resonance imaging (MRI) scans performed with a gadolinium contrast agent. A gadolinium contrast agent is used for about 30 percent of MRI scans to improve the clarity of the images. It is injected into the patient then excreted out of the body in urine within 24 hours.

Lewis Shin, MD, assistant professor of radiology and a MRI radiologist, explained to me the importance of using intravenous gadolinium contrast agents:

“Gadolinium contrast agents allow us to detect abnormalities that would otherwise be hidden from view and to improve our characterization of the abnormalities that we do find. Gadolinium is not always used; for example, if a physician is just concerned about identifying a herniated disk in the spine, an MRI without contrast agent is sufficient.

However, gadolinium is routinely administered to detect and characterize lesions if there is a clinical concern of cancer. Also, if a patient was previously treated for cancer, gadolinium administration is often extremely helpful to detect early recurrences. In summary, MRI with a gadolinium contrast agent greatly improves our ability to make an accurate diagnosis not only for cancer but for many other disease processes as well.”

According to UCSC researchers, gadolinium is not removed by standard wastewater treatment technologies, so it is discharged by wastewater treatment plants into surface waters that reach the Bay.

Shin expressed some surprise when he learned about this study:

“The majority of radiologists probably don’t even think about gadolinium once it’s excreted out of a patient’s body. Of course it’s concerning that there is a rise in gadolinium levels in the environment, but the next questions are how is this impacting the environment and whether there is a safe level or not? Since most of the gadolinium contrast agents used for MRI studies are excreted through the urine within 12 to 24 hours, one strategy to reduce environmental release of gadolinium could be to collect patients’ urine for a brief period of time for proper disposal or even recycling of the gadolinium itself.”

The UCSC researchers assert that the current levels of gadolinium observed in San Francisco Bay are well below the peak concentrations that could pose harmful effects on the aquatic ecosystem. However, they recommend in their paper, “new public policies and the development of more effective treatment technologies may be necessary to control sources and minimize future contamination.”

This is a reposting of my Scope blog story, courtesy of Stanford School of Medicine.

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