Evaluation of the timing and regional distribution of 18 psychoactive drugs and metabolites in a Chinese city by wastewater analysis

In recent years, mental disorders have become serious health problems. Monitoring the usage of psychotropic drugs can reflect the prevalence of mental disorders in the population, and wastewater analysis is an effective method for monitoring the use of psychoactive pharmaceuticals. In our study, we collected 58 samples from 12 wastewater treatment plants (WWTPs) in a southern city in China. We then analyzed the concentrations and loads of 18 frequently used psychoactive drugs and corresponding metabolites. The most abundant compounds in wastewater were diazepam, sulpiride, clozapine, venlafaxine, and quetiapine, with a detection frequency close to 100%. Sulpiride had the highest average load, followed by venlafaxine, clozapine, quetiapine, and diazepam. The higher load of diazepam in suburban WWTPs than in urban WWTPs reflects the large numbers of older people living in suburban areas in most of China. The lower loads of most target compounds in suburban WWTPs than in urban WWTPs indicate a greater likelihood of mental disorders in urban people than in suburban people. A correlation analysis of the target compounds revealed a correlation between the occurrence of venlafaxine, sulpiride, and clozapine. Overall, wastewater analysis is expected to be a significant tool for monitoring the consumption of psychoactive pharmaceuticals.