Occurrence and Behavior of X-ray Contrast Media in Sewage Facilities and the Aquatic Environment

The occurrence of iodinated X-ray contrast media derived from radiological examinations was investigated in German municipal sewage, sewage treatment plant (STP) effluents, rivers, and groundwater using LC-electrospray tandem MS detection. The four X-ray contrast media, diatrizoate, iopamidol, iopromide, and iomeprol are ubiquitously distributed in the sewage and in the aquatic environment. The X-ray contrast media were not significantly eliminated during the sewage treatment processes close to Frankfurt/Main. On weekdays the loading of the X-ray contrast media was significantly increased, because X-ray examinations are performed in hospitals and radiological practices predominately from Monday to Friday. The maximum concentration measured in STP effluents was 15 μg/L for iopamidol. Due to the high contamination of STP effluents with X-ray contrast media, the respective receiving waters (rivers and creeks) were also highly polluted. Median values up to 0.49 μg/L for iopamidol and 0.23 μg/L for diatrizoate were determined. In groundwater these polar compounds were present up to concentrations as high as 2.4 μg/L for iopamidol. Since X-ray contrast media are predominantly applied in human medicine, the polluted municipal STP effluents are presumably the sole sources for the contamination of the aquatic environment.