Drugs of abuse and their metabolites in the urban rivers of Beijing, China: Occurrence, distribution, and potential environmental risk.

The occurrence and distribution of five drugs of abuse and their metabolites, namely, methamphetamine (METH), amphetamine (AMP), ketamine (KET), ephedrine (EPH), and hydroxylimine (HY), were investigated in the surface water in urban rivers in Beijing, China. A total of 117 surface water samples were collected from the seven rivers in the Beijing urban areas during four different seasons. Laboratory analyses revealed that EPH and METH were the most predominant drugs, with detection frequency ranging from 94% to 100% and from 65% to 100%, respectively. High levels of METH and KET were observed in the center part of the urban areas, which was likely associated with the drug abuse and the entertainment activities. Seasonal variation of the drug occurrence showed that the highest concentration of drugs of abuse was found during winter, which was likely due to the high consumption, low temperature, and low water flows during the cold weather. By contrast, the concentration and detection frequency of AMP and HY were relatively low. Risk assessment by the risk quotient method indicated that the five drugs of abuse and their metabolites were not likely to exert biological effects on the aquatic ecosystems at current levels in the surface water. However, the potential adverse effect of drugs of abuse and their metabolites on ecosystem functioning and human health should not be neglected.