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Research in the United States evaluating ecotoxic risk to receiving waters posed by contaminants occurring in wastewater discharges typically has focused on measurements of pharmaceuticals and personal care products (PPCPs), with limited evaluations of UV filters and phenylpyrazole and neonicotinoid pesticides. In this study, concentrations of 5 representative pharmaceuticals, 11 pesticides or pesticide degradation products, and 5 ultraviolet filters were measured in 24 h composite samples of six wastewater discharges representing ∼70% of the total wastewater discharged to San Francisco Bay during the summer and fall of 2021. No significant difference was observed between concentrations measured on weekdays vs. weekends. A hydrodynamic model of San Francisco Bay was used to estimate annual average dilution factors associated with different subembayments. With and without considering dilution effects, Risk Quotients were calculated using the 90th percentile of measured concentrations in wastewater effluents and threshold concentrations associated with ecotoxicity. Risk Quotients were highest for the neonicotinoid pesticide, imidacloprid, and exceeded ecotoxicity thresholds in the lower South Bay by a factor of 2.4, even when considering dilution. Compared to commonly measured pharmaceuticals, Risk Quotients for imidacloprid were higher than those for carbamazepine, trimethoprim and diclofenac, and comparable to those for propranolol and metoprolol. Risk Quotients for the pesticide, fipronil, and the UV filter, oxybenzone, were higher than for carbamazepine. The results highlight the need to incorporate pesticides and UV filters with high Risk Quotients into studies in the United States evaluating ecotoxic risk associated with contaminants in municipal wastewater discharges.

Ultraviolet (UV) radiation filters are chemicals designed to absorb or reflect harmful solar radiation, and are used in products as diverse as personal care products (e.g., sunscreens, lotions, and cosmetics) and industrial products (e.g., insecticides, plastics, and paints) to mitigate deleterious effects of sunlight and extend product life. Widespread use of UV filters has led to extensive detections in the environment, and have raised concerns about impacts to aquatic ecosystems. In particular, several organic UV filters that are commonly used in sunscreen have been identified as neurotoxins and endocrine disruptors. To help understand the presence of organic UV filters and their potential to pose risks in San Francisco Bay, three of the most commonly used organic UV filters used in sunscreen (avobenzone, octinoxate, oxybenzone) as well as select metabolites were analyzed in municipal wastewater effluent from the six largest publicly-owned treatment works (POTWs) discharging into the Bay. Note that organic UV filters is a broad chemical class, and other constituents within this class were not included in this study.

Only two of the three organic UV filters analyzed were detected in effluent, avobenzone (detected in 70% of samples) and oxybenzone (83%), with median concentrations of 28 and 86 ng/L, and 90th percentile concentrations of 77 and 209 ng/L, respectively. Concentrations of avobenzone and oxybenzone varied widely across facilities, though there were no clear outlier values. The two POTWs utilizing advanced secondary treatment had the lowest concentrations of any facilities, which may indicate increased removal from these processes. Overall, these concentrations were higher than those reported in one other study of wastewater effluent in the US. An increasing body of literature will help to fully understand the occurrence and fate of organic UV filters in wastewater.