Impact on gadolinium anomaly in river waters in Tokyo related to the increased number of MRI devices in use

The Gd-based contrast agents utilized in magnetic resonance imaging are difficult to remove by usual sewage treatment technology, and they enter rivers in the discharges from waste water treatment plants. Gd anomaly in rivers has been considered depends on used amount of Gd-based contrast agents. In this study, variation of Gd anomaly in rivers of Tokyo was determined by comparisons to previously reported values. The range of anthropogenic Gd was 0.1–138.8 ppt with an average value of 35.5 ppt (n = 40); in particular, the anthropogenic Gd was significantly changed depending on the location of the waste water treatment plants, and the measurement revealed significant increases in the Gd anomaly in the range of 5.0–6.6 times compared to data obtained 22 years ago. This study highlights the necessary of continuous research in setting new public policies for medical practices. •Gd anomaly in Tokyo rivers due to Gd-based contrast agent use was determined.•Gd-based contrast agents behave conservatively in the environment.•Gd anomaly was associated with MRI apparatus numbers and medical practice level.•Close attention should be paid to future Gd anomaly trends.