Occurrence and Spatiotemporal Dynamics of Pharmaceuticals in a Temperate-Region Wastewater Effluent-Dominated Stream: Variable Inputs and Differential Attenuation Yield Evolving Complex Exposure Mixtures

Apportioning sources of chemicals of emerging concern along an urban river with inverse modelling

Concentrations of chemicals in river water provide crucial information for assessing environmental exposure and risks from fertilisers, pesticides, heavy metals, illicit drugs, pathogens, pharmaceuticals, plastics and perfluorinated substances, among others. However, using concentrations measured along waterways (e.g., from grab samples) to identify sources of contaminants and understand their fate is complicated by mixing of chemicals downstream from diverse diffuse and point sources (e.g., agricultural runoff, wastewater treatment plants). To address this challenge, a novel inverse modelling approach is presented. Using waterway network topology, it quantifies locations and concentrations of contaminant sources upstream by inverting concentrations measured in water samples. It is computationally efficient and quantifies uncertainty. The approach is demonstrated for 13 contaminants of emerging concern (CECs) in an urban stream, the R. Wandle (London, UK). Mixing (the forward problem) was assumed to be conservative, and the location of sources and their concentrations were treated as unknowns to be identified. Calculated CEC source concentrations, which ranged from below detection limit (a few ng/L) up to 1μg/L, were used to predict concentrations of chemicals downstream. Using this approach, >90% of data were predicted within observational uncertainty. Principal component analysis of calculated source concentrations revealed signatures of two distinct chemical sources. First, pharmaceuticals and insecticides were associated with a subcatchment containing a known point source of treated effluent from a wastewater treatment plant. Second, illicit drugs and salicylic acid were associated with multiple sources, interpreted as input from untreated sewage including Combined Sewer Overflows (CSOs), misconnections, runoff and direct disposal throughout the catchment. Finally, a simple algorithmic approach that incorporates network topology was developed to design sampling campaigns to improve resolution of source apportionment. Inverse modelling of contaminant measurements can provide objective means to apportion sources in waterways from spot samples in catchments on a large scale.

Pesticides and PPCPs in aquatic ecosystems of the andean central region: Occurrence and ecological risk assessment in the Uco valley

Uco valley (Mendoza, Argentina) suffers the concomitant effect of climate change, anthropic pressure and water scarcity. Moreover chemical pollution to aquatic ecosystems could be another pressuring factor, but it was not studied enough to the present. In this sense, the aim of this study was to assess the occurrence of pesticides, pharmaceuticals and personal care products (PPCPs) in aquatic ecosystems of the Uco Valley and to perform an ecological risk assessment (ERA). The presence of several insecticides (mainly neonicotinoids), herbicides (atrazine, diuron, metolachlor, terbutryn) and fungicides (strobilurins, triazolic and benzimidazolic compounds) in water samples in two seasons, related to crops like vineyards, garlic or fruit trees was associated to medium and high-risk probabilities for aquatic biota. Moreover, PPCPs of the group of non-steroidal anti-inflammatory drugs, parabens and bisphenol A were detected in all the samples and their calculated risk quotients also indicated a high risk. This is the first record of pesticides and PPCPs with an ERA in this growing agricultural oasis. Despite the importance of these findings in Uco Valley for decision makers in the region, this multilevel approach could bring a wide variety of tools for similar regions in with similar productive and environmental conditions, in order to afford actions to reach Sustainable Development Goals. SYNOPSIS: Aquatic ecosystems in arid mountain regions are threatened worldwide. This study reports relevant data about chemical pollution in Central Andes, which could be a useful tool to enhance SDGs' accomplishment.

Environmental Risks of Pharmaceutical Mixtures in Aquatic Ecosystems: Reflections on a Decade of Research

Pharmaceuticals and personal care products (PPCPs) occur as variable mixtures in surface waters receiving discharges of human and animal wastes. A key question identified a decade ago is how to assess the effects of long-term exposures of these PPCP mixtures on nontarget organisms. We review the recent progress made on assessing the aquatic ecotoxicity of PPCP mixtures-with a focus on active pharmaceutical ingredients-and the challenges and research needs that remain. New knowledge has arisen from the use of whole-mixture testing combined with component-based approaches, and these studies show that mixtures often result in responses that meet the concentration addition model. However, such studies have mainly been done on individual species over shorter time periods, and longer-term, multispecies assessments remain limited. The recent use of targeted and nontargeted gene analyses has improved our understanding of the diverse pathways that are impacted, and there are promising new "read-across" methods that use mammalian data to predict toxicity in wildlife. Risk assessments remain challenging given the paucity of ecotoxicological and exposure data on PPCP mixtures. As such, the assessment of PPCP mixtures in aquatic environments should remain a priority given the potential for additive-as well as nontarget-effects in nontarget organisms. In addition, we need to improve our understanding of which species, life stages, and relevant endpoints are most sensitive to which types of PPCP mixtures and to expand our knowledge of environmental PPCP levels in regions of the globe that have been poorly studied to date. We recommend an increased use of new approach methodologies, in particular "omics," to advance our understanding of the molecular mechanics of mixture effects. Finally, we call for systematic research on the role of PPCP mixtures in the development of antimicrobial resistance. Environ Toxicol Chem 2024;43:549-558. © 2023 SETAC.

Methylation and Demethylation of Emerging Contaminants in Plants

Many contaminants of emerging concern (CECs) have reactive functional groups and may readily undergo biotransformations, such as methylation and demethylation. These transformations have been reported to occur during human metabolism and wastewater treatment, leading to the propagation of CECs. When treated wastewater and biosolids are used in agriculture, CECs and their transformation products (TPs) are introduced into soil-plant systems. However, little is known about whether transformation cycles, such as methylation and demethylation, take place in higher plants and hence affect the fate of CECs in terrestrial ecosystems. In this study, we explored the interconversion between four common CECs (acetaminophen, diazepam, methylparaben, and naproxen) and their methylated or demethylated TPs in Arabidopsis thaliana cells and whole wheat seedlings. The methylation-demethylation cycle occurred in both plant models with demethylation generally taking place at a greater degree than methylation. The transformation rate of demethylation or methylation was dependent on the bond strength of R-CH3, with demethylation of methylparaben or methylation of acetaminophen being more pronounced. Although not explored in this study, these interconversions may exert influences on the behavior and biological activity of CECs, particularly in terrestrial ecosystems. The study findings demonstrated the prevalence of transformation cycles between CECs and their methylated or demethylated TPs in higher plants, contributing to a more complete understanding of risks of CECs in the human-wastewater-soil-plant continuum.

Effects of Age and Exposure Duration on the Sensitivity of Early Life Stage Fathead Minnow (Pimephales promelas) to Waterborne Propranolol Exposure

Propranolol is a heavily prescribed, nonspecific beta-adrenoceptor (bAR) antagonist frequently found in wastewater effluents, prompting concern over its potential to adversely affect exposed organisms. In the present study, the transcriptional responses of 4, 5, and 6 days postfertilization (dpf) ±1 h fathead minnow, exposed for 6, 24, or 48 h to 0.66 or 3.3 mg/L (nominal) propranolol were characterized using RNA sequencing. The number of differentially expressed genes (DEGs) was used as an estimate of sensitivity. A trend toward increased sensitivity with age was observed; fish >7 dpf at the end of exposure were particularly sensitive to propranolol. The DEGs largely overlapped among treatment groups, suggesting a highly consistent response that was independent of age. Cluster analysis was performed using normalized count data for unexposed and propranolol-exposed fish. Control fish clustered tightly by age, with fish ≥7 dpf clustering away from younger fish, reflecting developmental differences. When clustering was conducted using exposed fish, in cases where propranolol induced a minimal or no transcriptional response, the results mirrored those of the control fish and did not appreciably cluster by treatment. In treatment groups that displayed a more robust transcriptional response, the effects of propranolol were evident; however, fish <7 dpf clustered away from older fish, despite having similar numbers of DEGs. Increased sensitivity at 7 dpf coincided with developmental milestones with the potential to alter propranolol pharmacokinetics or pharmacodynamics, such as the onset of exogenous feeding and gill functionality as well as increased systemic expression of bAR. These results may have broader implications because toxicity testing often utilizes fish <4 dpf, prior to the onset of these potentially important developmental milestones, which may result in an underestimation of risk for some chemicals. Environ Toxicol Chem 2024;00:1-14. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

Relevance of photocatalytic redox transformations of selected pharmaceuticals in a copper- and iron-rich Mediterranean intermittent river

This work aimed at investigating specific attenuation pathways of pharmaceuticals in copper- and iron-rich Mediterranean intermittent and sunlit rivers by combining lab- and field-scale studies. Poorly photodegradable and biodegradable compounds such as fluconazole, oxazepam and venlafaxine attenuated in two river stretches with short hydraulic residence times (<3 h). This result was assumed to be related to their capacity to interact with photoreactive free Cu2+ and Fe3+ or their associated oxides. Lab-scale photodegradation experiments under simulated solar irradiation revealed the beneficial impact of a mixture Cu2+ and colloidal iron hydroxides at environmental concentrations and at neutral pH on the pharmaceuticals photodegradation kinetic rate constants. These latter were consistent with the in-stream attenuation rate constants of targeted contaminants which ranged from 0.104 to 0.154 h-1. Further identification of phototransformation products by LC-HRMS highlighted reductive transformation pathways including reductive dehalogenation and hydrogenation reactions. Several TPs were found to be stable under irradiation and were detected in field monitoring, accordingly. This was ascribed to the formation of a Cu/Fe composite material under solar irradiation with photocatalytic properties. The role of Cu was to trap the electron in the conduction band of the iron-based photocatalyst, which promoted separation efficiency of electron-hole pairs as well as enhanced photoreduction processes at the expense of oxidation ones. Even though, these mechanisms have been reported in water treatment field for organic micropollutants removal, their significance was demonstrated for the first time in natural settings.

Wastewater discharges alter microbial community composition in surface waters of the canadian prairies

Microbial communities are an important component of freshwater biodiversity that is threatened by anthropogenic impacts. Wastewater discharges pose a particular concern by being major sources of anthropogenic contaminants and microorganisms that may influence the composition of natural microbial communities. Nevertheless, the effects of wastewater treatment plant (WWTP) effluents on microbial communities remain largely unexplored. In this study, the effects of wastewater discharges on microbial communities from five different WWTPs in Southern Saskatchewan were investigated using rRNA gene metabarcoding. In parallel, nutrient levels and the presence of environmentally relevant organic pollutants were analyzed. Higher nutrient loads and pollutant concentrations resulted in significant changes in microbial community composition. The greatest changes were observed in Wascana Creek (Regina), which was found to be heavily polluted by wastewater discharges. Several taxa occurred in greater relative abundance in the wastewater-influenced stream segments, indicating anthropogenic pollution and eutrophication, especially taxa belonging to Proteobacteria, Bacteroidota, and Chlorophyta. Strong decreases were measured within the taxa Ciliphora, Diatomea, Dinoflagellata, Nematozoa, Ochrophyta, Protalveolata, and Rotifera. Across all sample types, a significant decline in sulfur bacteria was measured, implying changes in functional biodiversity. In addition, downstream of the Regina WWTP, an increase in cyanotoxins was detected which was correlated with a significant change in cyanobacterial community composition. Overall, these data suggest a causal relationship between anthropogenic pollution and changes in microbial communities, possibly reflecting an impairment of ecosystem health.

Spatiotemporal distribution of veterinary and human drugs and its predictability in Japanese catchments

Little is known about the predictability of mass flows of veterinary drugs in Asian catchments, where effluent from livestock farms is a major source. We therefore conducted this study to understand the applicability and limitations of a population-based emission model, which assumed usage of veterinary and human drugs to be evenly distributed over the national livestock or human population throughout the year, and sources to be effluent discharges at livestock farms, households, and sewage treatment plants in Japanese catchments. We monitored five veterinary drugs (lincomycin, sulfamonomethoxine, tiamulin, tylosin, and tilmicosin), two human and livestock drugs (sulfamethoxazole and trimethoprim), two human drugs (carbamazepine and clarithromycin), and a metabolite (sulfapyridine) of a human drug once a month over 2 years in eight Japanese rivers which have active livestock farming in their catchments. Mass flows of carbamazepine and sulfapyridine were stable, while those of veterinary drugs fluctuated widely, especially sulfamonomethoxine and tilmicosin, whose 25 %-100 % ranges averaged 1.5 and 1.2 log units, respectively, attributable mainly to their usage patterns. The model accurately predicted mean mass flows of carbamazepine in the rivers with errors of <±0.3 log unit. Although it slightly to moderately overestimated those of the other four human-related compounds, the incorporation of an empirical correction factor, determined to minimize mean absolute error (MAE) among the rivers, substantially lowered their MAEs to <0.23 log units. However, the MAEs of the five veterinary drugs were as high as 0.42 (sulfamonomethoxine) to 0.60 (tiamulin) log units even with the coefficient, likely due mainly to the spatial distribution of their usage per capita. So as not to overlook spatiotemporal elevation of risks of veterinary drugs, a stochastic method should be applied in their management. This is the first study to assess the use of spatiotemporal homogeneity in usage per capita of veterinary drugs in Asian catchments.

Nitrogen-doped magnetic porous carbon material from low-cost anion-exchange resin as an efficient adsorbent for tetracyclines in water

In this work, nitrogen-doped magnetic porous carbon material (N-MPC) was prepared through the high-temperature calcination of low-cost [Fe(CN)₆]^3--loaded anion-exchange resin, which was experimentally demonstrated to have significant adsorption performance for tetracycline (TC) in water. The N-MPC adsorbent with a large specific surface area (781.1 m² g^-1) was able to maintain excellent performance in a wide pH range from 4 to 10 or in high ionic strength solution. The adsorption of TC on N-MPC was found to be more consistent with the pseudo-second-order model and Langmuir adsorption model, and the maximum adsorption capacity (q_{m, cal}) was calculated to be 603.4 mg g^-1. As a recoverable magnetic adsorbent, the N-MPC remained a TC removal rate higher than 70% after four adsorption cycles. The adsorption mechanism was speculated on the basis of characterizations, where pore filling, hydrogen bonding interaction, and π-π electron donor-acceptor (EDA) interaction were crucial adsorption mechanisms. A variety of antibiotics were selected for adsorption, and excellent performance was found especially for TCs, indicating that the N-MPC can be used for the efficient removal of TCs from water.

Occurrence of Z-drugs, benzodiazepines, and ketamine in wastewater in the United States and Mexico during the Covid-19 pandemic

Z-drugs, benzodiazepines and ketamine are classes of psychotropic drugs prescribed for treating anxiety, sleep disorders and depression with known side effects including an elevated risk of addiction and substance misuse. These drugs have a strong potential for misuse, which has escalated over the years and was hypothesized here to have been exacerbated during the COVID-19 pandemic. Wastewater-based epidemiology (WBE) constitutes a fast, easy, and relatively inexpensive approach to epidemiological surveys for understanding the incidence and frequency of uses of these drugs. In this study, we analyzed wastewater (n = 376) from 50 cities across the United States and Mexico from July to October 2020 to estimate drug use rates during a pandemic event. Both time and flow proportional composite and grab samples of untreated municipal wastewater were analyzed using solid-phase extraction followed by liquid chromatography-tandem mass spectrometry to determine loadings of alprazolam, clonazepam, diazepam, ketamine, lorazepam, nordiazepam, temazepam, zolpidem, and zaleplon in raw wastewater. Simultaneously, prescription data of the aforementioned drugs were extracted from the Medicaid database from 2019 to 2021. Results showed high detection frequencies of ketamine (90 %), lorazepam (87 %), clonazepam (76 %) and temazepam (73 %) across both Mexico and United States and comparatively lower detection frequencies for zaleplon (22 %), zolpidem (9 %), nordiazepam (<1 %), diazepam (<1 %), and alprazolam (<1 %) during the pandemic. Average mass consumption rates, estimated using WBE and reported in units of mg/day/1000 persons, ranged between 62 (temazepam) and 1100 (clonazepam) in the United States. Results obtained from the Medicaid database also showed a significant change (p < 0.05) in the prescription volume between the first quarter of 2019 (before the pandemic) and the first quarter of 2021 (pandemic event) for alprazolam, clonazepam and lorazepam. Study results include the first detections of zaleplon and zolpidem in wastewater from North America.

Transcriptome signatures of wastewater effluent exposure in larval zebrafish vary with seasonal mixture composition in an effluent-dominated stream

Wastewater treatment plant (WWTP) effluent-dominated streams provide critical habitat for aquatic and terrestrial organisms but also continually expose them to complex mixtures of pharmaceuticals that can potentially impair growth, behavior, and reproduction. Currently, few biomarkers are available that relate to pharmaceutical-specific mechanisms of action. In the experiment reported in this paper, zebrafish (Danio rerio) embryos at two developmental stages were exposed to water samples from three sampling sites (0.1 km upstream of the outfall, at the effluent outfall, and 0.1 km below the outfall) during base-flow conditions from two months (January and May) of a temperate-region effluent-dominated stream containing a complex mixture of pharmaceuticals and other contaminants of emerging concern. RNA-sequencing identified potential biological impacts and biomarkers of WWTP effluent exposure that extend past traditional markers of endocrine disruption. Transcriptomics revealed changes to a wide range of biological functions and pathways including cardiac, neurological, visual, metabolic, and signaling pathways. These transcriptomic changes varied by developmental stage and displayed sensitivity to variable chemical composition and concentration of effluent, thus indicating a need for stage-specific biomarkers. Some transcripts are known to be associated with genes related to pharmaceuticals that were present in the collected samples. Although traditional biomarkers of endocrine disruption were not enriched in either month, a high estrogenicity signal was detected upstream in May and implicates the presence of unidentified chemical inputs not captured by the targeted chemical analysis. This work reveals associations between bioeffects of exposure, stage of development, and the composition of chemical mixtures in effluent-dominated surface water. The work underscores the importance of measuring effects beyond the endocrine system when assessing the impact of bioactive chemicals in WWTP effluent and identifies a need for non-targeted chemical analysis when bioeffects are not explained by the targeted analysis.

Contaminant Exposure and Transport from Three Potential Reuse Waters within a Single Watershed

Global demand for safe and sustainable water supplies necessitates a better understanding of contaminant exposures in potential reuse waters. In this study, we compared exposures and load contributions to surface water from the discharge of three reuse waters (wastewater effluent, urban stormwater, and agricultural runoff). Results document substantial and varying organic-chemical contribution to surface water from effluent discharges (e.g., disinfection byproducts [DBP], prescription pharmaceuticals, industrial/household chemicals), urban stormwater (e.g., polycyclic aromatic hydrocarbons, pesticides, nonprescription pharmaceuticals), and agricultural runoff (e.g., pesticides). Excluding DBPs, episodic storm-event organic concentrations and loads from urban stormwater were comparable to and often exceeded those of daily wastewater-effluent discharges. We also assessed if wastewater-effluent irrigation to corn resulted in measurable effects on organic-chemical concentrations in rain-induced agricultural runoff and harvested feedstock. Overall, the target-organic load of 491 g from wastewater-effluent irrigation to the study corn field during the 2019 growing season did not produce substantial dissolved organic-contaminant contributions in subsequent rain-induced runoff events. Out of the 140 detected organics in source wastewater-effluent irrigation, only imidacloprid and estrone had concentrations that resulted in observable differences between rain-induced agricultural runoff from the effluent-irrigated and nonirrigated corn fields. Analyses of pharmaceuticals and per-/polyfluoroalkyl substances in at-harvest corn-plant samples detected two prescription antibiotics, norfloxacin and ciprofloxacin, at concentrations of 36 and 70 ng/g, respectively, in effluent-irrigated corn-plant samples; no contaminants were detected in noneffluent irrigated corn-plant samples.

Influence of methylation and demethylation on plant uptake of emerging contaminants

Contaminants of emerging concern (CECs) as well as their transformation products (TPs) are often found in treated wastewater and biosolids, raising concerns about their environmental risks. Small changes in chemical structure, such as the addition or loss of a methyl group, as the result of methylation or demethylation reaction, may significantly alter a chemical's physicochemical properties. In this study, we evaluated the difference in accumulation and translocation between four CECs and their respective methylated or demethylated derivatives in plant models. Suspended Arabidopsis thaliana cell culture and wheat seedlings were cultivated in nutrient solutions containing individual compounds at 1 mg/L. The methylated counterparts were generally more hydrophobic and showed comparative or greater accumulation in both plant models. For example, after 1 h incubation, methylparaben was found in A. thaliana cells at levels two orders of magnitude greater than demethylated methylparaben. In contrast, the demethylated counterparts, especially those with the addition of a hydroxyl group after demethylation, showed decreased plant uptake and limited translocation. For example, acetaminophen and demethylated naproxen were not detected in the shoots of wheat seedlings after hydroponic exposure. Results from this study suggest that common transformations such as methylation and demethylation may affect the environmental fate of CECs, and should be considered to obtain a more comprehensive understanding of risks of CECs in the environment.

Persistence of N-oxides transformation products of tertiary amine drugs at lab and field studies

This work aimed at studying the formation and persistence of N-oxides transformation products (TPs) of tertiary amine drugs by combining laboratory and field studies relevant for surface water. A monitoring study using passive samplers was first achieved for assessing attenuation of selected pharmaceuticals and their related N-oxides and N-, O-dealkylated TPs (i.e., venlafaxine, tramadol, amisulpride and sulpiride) along a 1.7 km river stretch between two sampling sites. This study revealed the stability of tramadol-N-oxide, amisulpride-N-oxide and the fast dissipation of O-desmethylvenlafaxine-N-oxide, as well as the significance of N-oxidized TPs in comparison to N-dealkylated TPs and parent compounds in river. Lab-scale experiments were then implemented for a better understanding of their mechanisms of formation and degradation under aerobic water/sediment testing and under simulated solar photochemistry. N-oxidation reactions were always a minor transformation pathway under both degradation conditions with respect to N-and O-dealkylation reactions. The amount of generated N-oxides were similar for venlafaxine, tramadol and sulpiride and peaked in the 8.4-12.8% and <4% of their initial concentration (100 μg/L), during photodegradation and biodegradation experiments, respectively. Other transformation pathways such as hydroxylation and α-C-hydroxylation followed by oxidation to amide or dehydration were also identified. Investigated N-oxides TPs (except O-desmethylvenlafaxine-N-oxide) were found stable under solar photolysis and aerobic biodegradation with a very slight reverse reaction to parent compound observed for tramadol-N-oxide and amisulpride-N-oxide. Lab-scale degradation experiments were not able to anticipate the high occurrence levels of N-oxide compounds in the environment. This was most likely due to faster degradation kinetics and/or higher sorption to sediment of parent compounds and dealkylated TPs over N-oxide TPs, resulting in higher relative accumulation of the latter.

RNA-seq reveals potential gene biomarkers in fathead minnows (Pimephales promelas) for exposure to treated wastewater effluent

Discharged wastewater treatment plant (WWTP) effluent greatly contributes to the generation of complex mixtures of contaminants of emerging concern (CECs) in aquatic environments which often contain neuropharmaceuticals and other emerging contaminants that may impact neurological function. However, there is a paucity of knowledge on the neurological impacts of these exposures to aquatic organisms. In this study, caged fathead minnows (Pimephales promelas) were exposed in situ in a temperate-region effluent-dominated stream (i.e., Muddy Creek) in Coralville, Iowa, USA upstream and downstream of a WWTP effluent outfall. The pharmaceutical composition of Muddy Creek was recently characterized by our team and revealed many compounds there were at a low microgram to high nanogram per liter concentration. Total RNA sequencing analysis on brain tissues revealed 280 gene isoforms that were significantly differentially expressed in male fish and 293 gene isoforms in female fish between the upstream and downstream site. Only 66 (13%) of such gene isoforms overlapped amongst male and female fish, demonstrating sex-dependent impacts on neuronal gene expression. By using a systems biology approach paired with functional enrichment analyses, we identified several potential novel gene biomarkers for treated effluent exposure that could be used to expand monitoring of environmental effects with respect to complex CEC mixtures. Lastly, when comparing the results of this study to those that relied on a single-compound approach, there was relatively little overlap in terms of gene-specific effects. This discovery brings into question the application of single-compound exposures in accurately characterizing environmental risks of complex mixtures and for gene biomarker identification.

Metformin Contamination in Global Waters: Biotic and Abiotic Transformation, Byproduct Generation and Toxicity, and Evaluation as a Pharmaceutical Indicator

Metformin is the first-line antidiabetic drug and one of the most prescribed medications worldwide. Because of its ubiquitous occurrence in global waters and demonstrated ecotoxicity, metformin, as with other pharmaceuticals, has become a concerning emerging contaminant. Metformin is subject to transformation, producing numerous problematic transformation byproducts (TPs). The occurrence, removal, and toxicity of metformin have been continually reviewed; yet, a comprehensive analysis of its transformation pathways, byproduct generation, and the associated change in adverse effects is lacking. In this review, we provide a critical overview of the transformation fate of metformin during water treatments and natural processes and compile the 32 organic TPs generated from biotic and abiotic pathways. These TPs occur in aquatic systems worldwide along with metformin. Enhanced toxicity of several TPs compared to metformin has been demonstrated through organism tests and necessitates the development of complete mineralization techniques for metformin and more attention on TP monitoring. We also assess the potential of metformin to indicate overall contamination of pharmaceuticals in aquatic environments, and compared to the previously acknowledged ones, metformin is found to be a more robust or comparable indicator of such overall pharmaceutical contamination. In addition, we provide insightful avenues for future research on metformin.

Modeling Risk Dynamics of Contaminants of Emerging Concern in a Temperate-region Wastewater Effluent-dominated Stream

Wastewater effluent-dominated streams are becoming increasingly common worldwide, including in temperate regions, with potential impacts on ecological systems and drinking water sources. We recently quantified the occurrence/ spatiotemporal dynamics of pharmaceutical mixtures in a representative temperate-region wastewater effluent-dominated stream (Muddy Creek, Iowa) under baseflow conditions and characterized relevant fate processes. Herein, we quantified the ecological risk quotients (RQs) of 19 effluent-derived contaminants of emerging concern (CECs; including: 14 pharmaceuticals, 2 industrial chemicals, and 3 neonicotinoid insecticides) and 1 run-off-derived compound (atrazine) in the stream under baseflow conditions, and estimated the probabilistic risks of effluent-derived CECs under all-flow conditions (i.e., including runoff events) using stochastic risk modeling. We determined that 11 out of 20 CECs pose medium-to-high risks to local ecological systems (i.e., algae, invertebrates, fish) based on literature-derived acute effects under measured baseflow conditions. Stochastic risk modeling indicated decreased, but still problematic, risk of effluent-derived CECs (i.e., RQ≥0.1) under all-flow conditions when runoff events were included. Dilution of effluent-derived chemicals from storm flows thus only minimally decreased risk to aquatic biota in the effluent-dominated stream. We also modeled in-stream transport. Thirteen out of 14 pharmaceuticals persisted along the stream reach (median attenuation rate constant k<0.1 h^-1) and entered the Iowa River at elevated concentrations. Predicted and measured concentrations in the drinking water treatment plant were below the human health benchmarks. This study demonstrates the application of probabilistic risk assessments for effluent-derived CECs in a representative effluent-dominated stream under variable flow conditions (when measurements are less practical) and provides an enhanced prediction tool transferable to other effluent-dominated systems.

Contaminants of emerging concerns in recycled water: Fate and risks in agroecosystems

Recycled water (RW) has been increasingly recognized as a valuable source of water for alleviating the global water crisis. When RW is used for agricultural irrigation, many contaminants of emerging concern (CECs) are introduced into the agroecosystem. The ubiquity of CECs in field soil, combined with the toxic, carcinogenic, or endocrine-disrupting nature of some CECs, raises significant concerns over their potential risks to the environment and human health. Understanding such risks and delineating the fate processes of CECs in the water-soil-plant continuum contributes to the safe reuse of RW in agriculture. This review summarizes recent findings and provides an overview of CECs in the water-soil-plant continuum, including their occurrence in RW and irrigated soil, fate processes in agricultural soil, offsite transport including runoff and leaching, and plant uptake, metabolism, and accumulation. The potential ecological and human health risks of CECs are also discussed. Studies to date have shown limited accumulation of CECs in irrigated soils and plants, which may be attributed to multiple attenuation processes in the rhizosphere and plant, suggesting minimal health risks from RW-fed food crops. However, our collective understanding of CECs is rather limited and knowledge of their offsite movement and plant accumulation is particularly scarce for field conditions. Given a large number of CECs and their occurrence at trace levels, it is urgent to develop strategies to prioritize CECs so that future research efforts are focused on CECs with elevated risks for offsite contamination or plant accumulation. Irrigating specific crops such as feed crops and fruit trees may be a viable option to further minimize potential plant accumulation under field conditions. To promote the beneficial reuse of RW in agriculture, it is essential to understand the human health and ecological risks imposed by CEC mixtures and metabolites.

Accurate Removal of Toxic Organic Pollutants from Complex Water Matrices

Characteristic emerging pollutants at low concentration have raised much attention for causing a bottleneck in water remediation, especially in complex water matrices where high concentration of interferents coexist. In the future, tailored treatment methods are therefore of increasing significance for accurate removal of target pollutants in different water matrices. This critical review focuses on the overall strategies for accurately removing highly toxic emerging pollutants in the presence of typical interferents. The main difficulties hindering the improvement of selectivity in complex matrices are analyzed, implying that it is difficult to adopt a universal approach for multiple targets and water substrates. Selective methods based on assorted principles are proposed aiming to improve the anti-interference ability. Thus, typical approaches and fundamentals to achieve selectivity are subsequently summarized including their mechanism, superiority and inferior position, application scope, improvement method and the bottlenecks. The results show that different methods may be applicable to certain conditions and target pollutants. To better understand the mechanism of each selective method and further select the appropriate method, advanced methods for qualitative and quantitative characterization of selectivity are presented. The processes of adsorption, interaction, electron transfer, and bond breaking are discussed. Some comparable selective quantitative methods are helpful for promoting the development of related fields. The research framework of selectivity removal and its fundamentals are established. Presently, although continuous advances and remarkable achievements have been attained in the selective removal of characteristic organic pollutants, there are still various substantial challenges and opportunities. It is hopeful to inspire the researches on the new generation of water and wastewater treatment technology, which can selectively and preferentially treat characteristic pollutants, and establish a reliable research framework to lead the direction of environmental science.

Altered microbiomes of aquatic macroinvertebrates and riparian spiders downstream of municipal wastewater effluents

Municipal wastewater treatment plants (WWTPs) contain numerous contaminants, including antimicrobials, that could affect the composition of the beneficial bacterial communities associated with host aquatic organisms. There is also potential for these effects to transfer to terrestrial predators. Riparian spiders and five families of aquatic macroinvertebrates were collected from sites upstream and downstream of two WWTPs, Waterloo and Kitchener, discharging to the Grand River, Ontario, Canada. Whole-body microbiota were analyzed following the extraction, PCR amplification, and sequencing of bacterial DNA using the V3-V4 hypervariable regions of the 16S rRNA genetic barcode. Changes in the relative abundance of major microbiome phyla were observed in all downstream aquatic insects except Hydropsychidae caddisflies, which exhibited little site variation. Shannon alpha diversity differed among sites for Tetragnathidae spiders, Perlidae, Hydropsychidae, and Heptageniidae. Downstream of the Waterloo WWTP alpha diversity decreased in spiders, while downstream of the Kitchener WWTP this measure decreased in Perlidae and increased in spiders. Bray-Curtis beta diversity was dissimilar among sites in all invertebrate taxa; upstream sites differed from those downstream of Waterloo in spiders, Perlidae, and Hydropsychidae, and from those downstream of Kitchener in spiders, Perlidae, and Hydropsychidae. Finally, effluent-derived bacteria were found in the microbiomes of downstream spiders and aquatic insects and not upstream. Overall, results indicated that the microbiomes of invertebrates collected downstream differed from those collected upstream of WWTPs, which has implications for altered host health and transport of WWTP-derived bacteria through aquatic ecosystems.

Prioritization of antibiotic contaminants in China based on decennial national screening data and their persistence, bioaccumulation and toxicity

The potential adverse impacts of antibiotic contamination on environmental quality are generating increasing concern. Given that an alarming amount and variety of antibiotics have been used in China, a list of priority antibiotics is urgently needed to develop regulatory frameworks to control antibiotic use and monitor environmental pollution. This study established a new method of ranking priority antibiotics based on their prevalence (Pv), occurrence (O), persistence, and bioaccumulation, and toxicity (PBT) in the environment. The Pv and O criteria were weighted and quantified using the decennial national screening datasets (>15,000 concentration values for 105 candidate antibiotics in eight environmental compartments), and quantitative structure-activity relationships were used to estimate PBT values. A total of 26 high priority antibiotics were identified using the PvOPBT method, including 8 quinolones, 5 sulfonamides, 5 macrolides, 4 tetracyclines, 3 from other classes, and 1 unclassified antibiotic. For individual antibiotic classes, the β-lactams and aminoglycosides were ranked from no priority to low priority, whereas the macrolides and tetracyclines were ranked from medium to high priority. Although the PvOPBT ranking scores for the aqueous and solid phases demonstrated an apparent difference for some candidate antibiotics, eighteen antibiotics were ranked as high priority in both aqueous phases and solid phases and are suggested as the top priorities worthy of immediate attention. These top priority antibiotics are primarily utilized in animal husbandry within China. Therefore, urgent action is needed to limit the use of these top priority antibiotics in the animal industry.

Food, Beverage, and Feedstock Processing Facility Wastewater: a Unique and Underappreciated Source of Contaminants to U.S. Streams

Process wastewaters from food, beverage, and feedstock facilities, although regulated, are an under-investigated environmental contaminant source. Food process wastewaters (FPWWs) from 23 facilities in 17 U.S. states were sampled and documented for a plethora of chemical and microbial contaminants. Of the 576 analyzed organics, 184 (32%) were detected at least once, with concentrations as large as 143 μg L^-1 (6:2 fluorotelomer sulfonic acid), and as many as 47 were detected in a single FPWW sample. Cumulative per/polyfluoroalkyl substance concentrations up to 185 μg L^-1 and large pesticide transformation product concentrations (e.g., methomyl oxime, 40 μg L^-1; clothianidin TMG, 2.02 μg L^-1) were observed. Despite 48% of FPWW undergoing disinfection treatment prior to discharge, bacteria resistant to third-generation antibiotics were found in each facility type, and multiple bacterial groups were detected in all samples, including total coliforms. The exposure-activity ratios and toxicity quotients exceeded 1.0 in 13 and 22% of samples, respectively, indicating potential biological effects and toxicity to vertebrates and invertebrates associated with the discharge of FPWW. Organic contaminant profiles of FPWW differed from previously reported contaminant profiles of municipal effluents and urban storm water, indicating that FPWW is another important source of chemical and microbial contaminant mixtures discharged into receiving surface waters.

Occurrence and Distribution of Pharmaceuticals and Their Transformation Products in Luxembourgish Surface Waters

Pharmaceuticals and their transformation products (TPs) are continuously released into the aquatic environment via anthropogenic activity. To expand knowledge on the presence of pharmaceuticals and their known TPs in Luxembourgish rivers, 92 samples collected during routine monitoring events between 2019 and 2020 were investigated using nontarget analysis. Water samples were concentrated using solid-phase extraction and then analyzed using liquid chromatography coupled to a high-resolution mass spectrometer. Suspect screening was performed using several open source computational tools and resources including Shinyscreen (https://git-r3lab.uni.lu/eci/shinyscreen/), MetFrag (https://msbi.ipb-halle.de/MetFrag/), PubChemLite (https://zenodo.org/record/4432124), and MassBank (https://massbank.eu/MassBank/). A total of 94 pharmaceuticals, 88 confirmed at a level 1 confidence (86 of which could be quantified, two compounds too low to be quantified) and six identified at level 2a, were found to be present in Luxembourg rivers. Pharmaceutical TPs (12) were also found at a level 2a confidence. The pharmaceuticals were present at median concentrations up to 214 ng/L, with caffeine having a median concentration of 1424 ng/L. Antihypertensive drugs (15), psychoactive drugs (15), and antimicrobials (eight) were the most detected groups of pharmaceuticals. A spatiotemporal analysis of the data revealed areas with higher concentrations of the pharmaceuticals, as well as differences in pharmaceutical concentrations between 2019 and 2020. The results of this work will help guide activities for improving water management in the country and set baseline data for continuous monitoring and screening efforts, as well as for further open data and software developments.

Tandem field and laboratory approaches to quantify attenuation mechanisms of pharmaceutical and pharmaceutical transformation products in a wastewater effluent-dominated stream

Evolving complex mixtures of pharmaceuticals and transformation products in effluent-dominated streams pose potential impacts to aquatic species; thus, understanding the attenuation dynamics in the field and characterizing the prominent attenuation mechanisms of pharmaceuticals and their transformation products (TPs) is critical for hazard assessments. Herein, we determined the attenuation dynamics and the associated prominent mechanisms of pharmaceuticals and their corresponding TPs via a combined long-term field study and controlled laboratory experiments. For the field study, we quantified spatiotemporal exposure concentrations of five pharmaceuticals and six associated TPs in a small, temperate-region effluent-dominated stream during baseflow conditions where the wastewater plant was the main source of pharmaceuticals. We selected four sites (upstream, at, and two progressively downstream from effluent discharge) and collected water samples at 16 time points (64 samples in total, approximately twice monthly, depending on flows) for 1 year. Concurrently, we conducted photolysis, sorption, and biodegradation batch tests under controlled conditions to determine the major attenuation mechanisms. We observed 10-fold greater attenuation rates in the field compared to batch tests, demonstrating that connecting laboratory batch tests with field measurements to enhance predictive power is a critical need. Batch systems alone, often used for assessment, are useful for determining fate processes but poorly approximate in-stream attenuation kinetics. Sorption was the dominant attenuation process (t_1/2<7.7 d) for 5 of 11 compounds in the batch tests, while the other compounds (n = 6) persisted in the batch tests and along the 5.1 km stream reach. In-stream parent-to-product transformation was minimal. Differential attenuation contributed to the evolving pharmaceutical mixture and created changing exposure conditions with concomitant implications for aquatic and terrestrial biota. Tandem field and laboratory characterization can better inform modeling efforts for transport and risk assessments.

Dosing the Coast: Leaking Sewage Infrastructure Delivers Large Annual Doses and Dynamic Mixtures of Pharmaceuticals to Urban Rivers

Pharmaceuticals are commonly detected at low concentrations in surface waters, where they disrupt biological and ecological processes. Despite their ubiquity, the annual mass of pharmaceuticals exported from watersheds is rarely quantified. We used liquid chromatography-mass spectroscopy to screen for 92 pharmaceuticals in weekly samples from an urban stream network in Baltimore, MD, USA, that lacks wastewater treatment effluents. Across the network, we detected 37 unique compounds, with higher concentrations and more compounds in streams with higher population densities. We also used concentrations and stream discharge to calculate annual pharmaceutical loads at the watershed outlet, which range from less than 1 kg to ∼15 kg and are equivalent to tens of thousands of human doses. By calculating annual watershed mass balances for eight compounds, we show that ∼0.05 to ∼42% of the pharmaceuticals consumed by humans in this watershed are released to surface waters, with the importance of different pathways (leaking sewage vs treated wastewater effluent) differing among compounds. These results demonstrate the importance of developing, maintaining, and improving sewage infrastructure to protect water resources from pharmaceutical contamination.

Exposure and Transport of Alkaloids and Phytoestrogens from Soybeans to Agricultural Soils and Streams in the Midwestern United States

Phytotoxins are naturally produced toxins with potencies similar/higher than many anthropogenic micropollutants. Nevertheless, little is known regarding their environmental fate and off-field transport to streams. To fill this research gap, a network of six basins in the Midwestern United States with substantial soybean production was selected for the study. Stream water (n = 110), soybean plant tissues (n = 8), and soil samples (n = 16) were analyzed for 12 phytotoxins (5 alkaloids and 7 phytoestrogens) and 2 widely used herbicides (atrazine and metolachlor). Overall, at least 1 phytotoxin was detected in 82% of the samples, with as many as 11 phytotoxins detected in a single sample (median = 5), with a concentration range from below detection to 37 and 68 ng/L for alkaloids and phytoestrogens, respectively. In contrast, the herbicides were ubiquitously detected at substantially higher concentrations (atrazine: 99% and metolachlor: 83%; the concentrations range from below detection to 150 and 410 ng/L, respectively). There was an apparent seasonal pattern for phytotoxins, where occurrence prior to and during harvest season (September to November) and during the snow melt season (March) was higher than that in December-January. Runoff events increased phytotoxin and herbicide concentrations compared to those in base-flow conditions. Phytotoxin plant concentrations were orders of magnitude higher compared to those measured in soil and streams. These results demonstrate the potential exposure of aquatic and terrestrial organisms to soybean-derived phytotoxins.

Spatio-Temporal Distribution and Influencing Factors of Human and Veterinary Pharmaceuticals in the Tributary Surface Waters of the Han River Watershed, South Korea

Human and veterinary pharmaceuticals are being increasingly used for disease treatment; hence, their distribution and factors influencing them in the aquatic environment need to be investigated. This study observed the effect of human and animal populations, usage, purchasing criteria (prescription vs. non-prescription), and land use to identify the spatio-temporal distribution of eight pharmaceuticals at twenty-four sites of the tributaries of the Han River watershed. In rural areas, the mean concentration (detection frequency) of non-prescription pharmaceuticals (NPPs) was higher (lower) compared to that of prescription pharmaceuticals (PPs); in urban areas, a reverse trend was observed. Pharmaceutical concentrations in urban and rural areas were mainly affected by wastewater treatment plants (WWTPs) and non-point sources, respectively; concentrations were higher downstream (4.9 times) than upstream of the WWTPs. The concentration distribution (according to the target) was as follows: human–veterinary > human > veterinary. Correlation between total concentration and total usage of the pharmaceuticals was high, except for NPPs. Most livestock and land use (except cropland) were significantly positively correlated with pharmaceutical concentrations. Concentrations were mainly higher (1.5 times) during cold seasons than during warm seasons. The results of this study can assist policymakers in managing pharmaceutical pollutants while prioritizing emerging pollutants.

Record of trace organic contaminants in a river sediment core: From historical wastewater management to historical use

Some trace organic contaminants (TrOCs) can be considered as ubiquitous contaminants since the 1950s, and the study of their historical distribution within river sediments allows us to better understand the temporal variation of the chemical quality of sediments, and make assumptions about the most insightful forcings impacting these distributions. In this study, the occurrence of 41 TrOCs of various classes (i.e. pharmaceutical products and pesticides) was studied in a sedimentary core sampled in a disused dock along the Seine River, France. This core covers a 60 year-long period between 1944 and 2003, and 23 TrOCs were detected at least once. Their concentrations mainly ranged between 1 and 10 ng g^-1 within the core, except for tetracycline that exhibited higher concentrations (~hundreds of ng·g^-1). The dating of the core, based on previous studies, enabled the characterization of the changes since 1945, potentially impacted by (i) the sewer connectivity, (ii) the upgrading of wastewater treatment technologies, (iii) historical modifications in the use of each TrOC, and (iv) the sedimentary composition. In every case the deepest occurrence of each TrOC in the core matched its market authorization date, indicating the potential of TrOC to be used as chronomarkers. This study also reveals that the recent upgrading of wastewater treatment technologies within the watershed decreased the concentrations of each TrOC, despite an increase in TrOC diversity in the most recent years.

Emerging investigator series: municipal wastewater as a year-round point source of neonicotinoid insecticides that persist in an effluent-dominated stream

Neonicotinoids in aquatic systems have been predominantly associated with agriculture, but some are increasingly being linked to municipal wastewater. Thus, the aim of this work was to understand the municipal wastewater contribution to neonicotinoids in a representative, characterized effluent-dominated temperate-region stream. Our approach was to quantify the spatiotemporal concentrations of imidacloprid, clothianidin, thiamethoxam, and transformation product imidacloprid urea: 0.1 km upstream, the municipal wastewater effluent, and 0.1 and 5.1 km downstream from the wastewater outfall (collected twice-monthly for one year under baseflow conditions). Quantified results demonstrated that wastewater effluent was a point-source of imidacloprid (consistently) and clothianidin (episodically), where chronic invertebrate exposure benchmarks were exceeded for imidacloprid (36/52 samples; 3/52 > acute exposure benchmark) and clothianidin (8/52 samples). Neonicotinoids persisted downstream where mass loads were not significantly different than those in the effluent. The combined analysis of neonicotinoid effluent concentrations, instream seasonality, and registered uses in Iowa all indicate imidacloprid, and seasonally clothianidin, were driven by wastewater effluent, whereas thiamethoxam and imidacloprid urea were primarily from upstream non-point sources (or potential in-stream transformation for imidacloprid urea). This is the first study to quantify neonicotinoid persistence in an effluent-dominated stream throughout the year-implicating wastewater effluent as a point-source for imidacloprid (year-round) and clothianidin (seasonal). These findings suggest possible overlooked neonicotinoid indoor human exposure routes with subsequent implications for instream ecotoxicological exposure.

Identification of core micropollutants of Ergene River and their categorization based on spatiotemporal distribution

Ergene River is heavily utilized for irrigation of fields to grow the main stocks of rice, wheat, and sunflower of Turkey also exported to Europe; therefore, monitoring the river's water quality is crucial for public health. Although the river quality is routinely monitored, the evaluation of pollution based on micropollutants is limited. In this study, we measured 222 organic micropollutants in 300 samples collected from 75 different locations on the Ergene River between August 2017 and May 2018 using direct injection liquid chromatography-tandem spectrometry with optimized scheduled multiple reaction monitoring. In total, 165 micropollutants were detected at a range of concentrations between 1.90 ng/L and 1824.55 μg/L. Sixty-three chemical substances were recurrent micropollutants that were detected at least one location in all seasons. Among them, 41 chemical substances were identified as the core micropollutants of the Ergene River using data-driven clustering methods. Hexa(methoxymethyl)melamine, benzotriazoles, and benzalkonium chlorides were frequently detected core micropollutants with an industrial origin. Besides, diuron, carbendazim, and cadusafos were common pesticides in the river. Core micropollutants were further categorized based on their type of source and environmental behavior using Kurtosis of concentration and load data obtained for each micropollutant. As a result, the majority of the core micropollutants are recalcitrant chemicals either released from a specific source located upstream of the river or have urban and agricultural sources dispersed on the watershed. In this study, we assessed the current state of pollution in the Ergene River at the micropollutant level with a very high spatial resolution and developed a statistical approach to categorize micropollutants that can be used to monitor the extent of pollution and track pollution sources in the river.