Quaternary ammonium compounds in wastewater during the COVID-19 pandemic: occurrence, exposure evaluation and risk assessment

Quaternary ammonium compounds (QACs) are widely used as active ingredients in cleaning products and personal care products, which could enter domestic wastewater through various daily human activities. During the COVID-19 pandemic, elevated usage of QACs was reported; however, whether the increase could pose potential risks to the environment and human health is still unknown. To evaluate the population exposure and risks of QACs, influent and effluent wastewater samples were collected from December 15, 2022, to January 31, 2023, in a wastewater treatment plant. QACs were detected at mean ΣQAC concentrations of 711 ng L^-1 in influent and 50.4 ng L^-1 in effluent. Dialkyldimethyl ammonium compounds (DADMACs) and benzylalkyldimethyl ammonium compounds (BACs) accounted for the largest mean proportion of 48.5% and 66.1% in influent and effluent, respectively. The evaluated daily ΣQAC exposure ranged from 0.309 to 2114 mg per 1000 residents during the sampling period. Most QACs could be removed, with mean removal efficiency in the range of 62.6-100%. DADMAC-14:14, DADMAC-16:16 and BAC-C12 in effluent displayed higher risks to aquatic organisms based on risk quotient calculation. The estimated daily intakes of QACs were below the reference dose, suggesting negligible health concerns. The environmental occurrence and physico-chemical properties were further integrated in the toxicological priority index approach to rank the monitored QACs. DADMAC-16:16 exhibited the highest score, indicating its priority in further environmental and toxicological research.