Wastewater-based monitoring of antipyretics use during COVID-19 outbreak in China and its associated ecological risks.

At the end of 2022, a sudden policy shift in China triggered an unprecedented COVID-19 outbreak that led to a dramatic increase in the consumption of antipyretics. In this study, the occurrence of the two most commonly used antipyretics (ibuprofen and paracetamol) and their metabolites were analyzed in the wastewater of nine major cities in China, covering the periods before, during, and after the policy change. The remarkable surge after the policy change for ibuprofen and paracetamol reached 67 times (in Nanning) and 311 times (in Lanzhou) compared to pre-pandemic levels, respectively. The variation of increases was mainly affected by the availability and the sampling period. During the outbreak period, direct discharge of high-drug-load wastewater could cause even higher risks; the RQ values were 0.43 for invertebrates in Lanzhou and 0.30 for fish in Nanning. Furthermore, during the post-pandemic period, wastewater discharge might pose high risks (RQ value was 2.58 in Xining to algae) associated with ibuprofen chronic toxicity. Fortunately, wastewater treatments would significantly reduce this risk to a low level (RQ<0.1). In some less developed areas, the lack of a comprehensive wastewater treatment system may lead to the direct discharge of untreated wastewater due to exfiltration of sewers, overflow of combined sewers, or lack of centralized or decentralized treatment facilities. Establishing a comprehensive wastewater treatment system is of great importance, especially in remote and impoverished areas. These results indicated that the potential ecological risks associated with epidemic outbreaks should not be overlooked. These risks may be heightened due to acute toxicity during health incidents, such as the COVID-19 outbreak, providing valuable insights for ecological management in future public health crises.