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 mu g/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 mu g/L for iopamidol and 0.23 mu g/L far diatrizoate were determined. in groundwater these polar compounds were present up to concentrations as high as 2.4 mu g/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.