Suspect Screening of Pharmaceuticals and Their Transformation Products (TPs) in Wastewater during COVID-19 Infection Peak: Identification of New TPs and Elevated Risks

Pharmaceuticals and their transformation products (TPs) in wastewater are emerging contaminants that pose risks to ecosystems and human health. Here, a typical period marked by the easing of the "zero-COVID" policy in December 2022, resulting in unprecedented infections in China, was chosen to illustrate the environmental impact of pharmaceutical usage during the COVID-19 pandemic. A suspect screening workflow was developed to identify pharmaceuticals and transformation products (TPs) in wastewater influent and effluent from a wastewater treatment plant (WWTP) during the peak and postpeak periods of COVID-19, integrating medication recommendations and TPs' prediction. A total of 114 pharmaceuticals and TPs were identified (13 TPs were detected for the first time in WWTP) by using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS). Wastewater-based epidemiology analysis showed that the most predominant pharmaceuticals were nonsteroidal anti-inflammatory drugs. Interestingly, the consumption of propafenone increased after the infection peak, possibly linked to long COVID-19 symptoms. Risks were further evaluated based on concentration, detection frequency, and PMT (persistence, mobility, and toxicity) properties, revealing that TPs of aminopyrine, acetaminophen, etc. showed even greater ToxPi scores than their parent compounds. This study highlights the elevated risks posed by pharmaceutical discharge during epidemics and the necessity for TPs' monitoring.