The end of 2019 was marked by reports of a previously unknown virus causing coronavirus disease 19 (COVID-19). With over 800 new daily hospitalizations at the peak in Los Angeles (LA) County, the potential for high use of COVID-19 treatment agents, remdesivir and dexamethasone, warranted a screening assessment of their fate and toxicity risk for aquatic organisms. We predicted environmental concentrations (PECs) using the ChemFate model and hospitalizations data and compared them to predicted ecotoxicity concentrations generated using Ecological Structure Activity Relationships (ECOSAR) to assess risk to potentially exposed organisms. The lowest predicted toxicity thresholds were between 2 and 11 orders of magnitude greater than the highest PECs for freshwater and saltwater. We conclude that had all eligible patients in LA County been given the recommended treatment regimen, exposure of aquatic organisms in regional water bodies to remdesivir, dexamethasone, and their evaluated metabolites would not be likely to be affected based on ECOSAR predictions. Conservative, protective assumptions were used for this screening analysis, considering limited toxicity information. Modeling tools thus serve to predict environmental concentrations and estimate ecotoxicity risks of novel treatment agents and can provide useful preliminary data to assess and manage ecological health risks.
Per-and polyfluoroalkyl substances (PFAS) have received increased scrutiny from environmental and public health protection agencies, with focus placed on phased-out "legacy" PFAS such as perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA). However, recent studies highlight the need to also evaluate the risks of replacement and breakdown products such as perfluorobutanesulfonic acid (PFBS) and hexafluoropropylene oxide dimer acid (HFPO-DA). Thus, the objective was to evaluate the ecological risks of legacy and newer PFAS, using monitoring and predictive models. Here, PFBS, PFOA, PFOS, and other PFAS were detected in samples collected downstream from 16 Southern and Central California wastewater treatment plants (WWTPs). PFBS, PFOA, and PFOS were sometimes detected at concentrations above experimentally determined lowest observed effect concentrations. Additionally, ChemFate, a fate and transport model, was used to estimate daily loads to the upstream WWTPs. Population size and urban land use were the best predictors of PFAS loads to WWTPs. The sum of influent loads of selected PFAS was estimated to be 61,000 ± 40,000 kg/year for California. Additionally, the sum of PFAS totaled annually in evaluated regions correlated well with the overall pollution burden. Here, the practicality of using predictive models in conjunction with field sampling to predict PFAS inputs and their ecological risks to the environment was demonstrated.
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