Occurrence of Natural and Synthetic Glucocorticoids in Sewage Treatment Plants and Receiving River Waters

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Abstract
This paper first reports the occurrence of six glucocorticoids (prednisone, prednisolone, cortisone, cortisol, dexamethasone, and 6α-methylprednisolone) in sewage treatment plants (STPs) and receiving rivers by establishing a method for analyzing glucocorticoids in complex environmental waters. For the various types of aqueous matrices considered, the absolute recoveries were from 73 to 99%, and limits of quantification were below 0.2 ng/L. Among the seven STPs studied, the average concentrations of prednisone, prednisolone, cortisone, cortisol, dexamethasone, and 6α-methylprednisolone in influents were, respectively, 2.6 ± 2.1, 3.0 ± 1.6, 30 ± 21, 39 ± 26, 1.2 ± 0.70, and 0.62 ± 0.65 ng/L, and their percent removals were 99 ± 3.1, 78 ± 8.8, 99 ± 1.2, 98 ± 2.5, 99 ± 1.8, and 100 ± 0%, respectively. The lower removal of prednisolone was found to be due to its relatively low efficiency of biodegradation, especially in anoxic and aerobic units. The frequently detected glucocorticoids in effluents were prednisolone, cortisol, and cortisone with average concentrations 0.56 ± 0.06, 0.50 ± 0.33, and 0.26 ± 0.10 ng/L. In the receiving waters, the Tonghui and Qing Rivers, the concentrations of these compounds in some samples were much higher than those in their corresponding STP effluents; these differences depended on the sampling date, suggesting that there was random discharging of untreated wastewaters into these rivers. In addition, the ratio between the combined concentrations of two natural glucocorticoids (cortisol and cortisone) and the concentration of one synthetic glucocorticoid, prednisolone, was found to be a potential index to reflect the wastewater discharging.