Metformin exposure at environmentally relevant concentrations causes potential endocrine disruption in adult male fish

Causal prior-embedded physics-informed neural networks and a case study on metformin transport in porous media

This study introduces a novel approach to transport modelling by integrating experimentally derived causal priors into neural networks. We illustrate this paradigm using a case study of metformin, a ubiquitous pharmaceutical emerging pollutant, and its transport behaviour in sandy media. Specifically, data from metformin's sandy column transport experiment was used to estimate unobservable parameters through a physics-based model Hydrus-1D, followed by a data augmentation to produce a more comprehensive dataset. A causal graph incorporating key variables was constructed, aiding in identifying impactful variables and estimating their causal dynamics or "causal prior." The causal priors extracted from the augmented dataset included underexplored system parameters such as the type-1 sorption fraction F, first-order reaction rate coefficient α, and transport system scale. Their moderate impact on the transport process has been quantitatively evaluated (normalized causal effect 0.0423, -0.1447 and -0.0351, respectively) with adequate confounders considered for the first time. The prior was later embedded into multilayer neural networks via two methods: causal weight initialization and causal prior regularization. Based on the results from AutoML hyperparameter tuning experiments, using two embedding methods simultaneously emerged as a more advantageous practice since our proposed causal weight initialization technique can enhance model stability, particularly when used in conjunction with causal prior regularization. amongst those experiments utilizing both techniques, the R-squared values peaked at 0.881. This study demonstrates a balanced approach between expert knowledge and data-driven methods, providing enhanced interpretability in black-box models such as neural networks for environmental modelling.

Surface functionalization, particle size and pharmaceutical co-contaminant dependent impact of nanoplastics on marine crustacean - Artemia salina

Despite a significant amount of research on micronanoplastics (MNPs), there is still a gap in our understanding of their function as transporters of other environmental pollutants (known as the Trojan horse effect) and the combined effects of ingestion, bioaccumulation, and toxicity to organisms. This study examined the individual effects of polystyrene nanoplastics (PSNPs) with various surface functionalizations (plain (PS), carboxylated (PS-COOH), and aminated (PS-NH2)), particle sizes (100 nm and 500 nm), and a pharmaceutical co-contaminant (metformin hydrochloride (MH), an anti-diabetic drug) on the marine crustacean - Artemia salina. The study specifically aimed to determine if MH alters the detrimental effects of PSNPs on A. salina. The potential toxicity of these emerging pollutants was assessed by examining mortality, hatching rate, morphological changes, and biochemical changes. Smaller nanoparticles had a more significant impact than larger ones, and PS-NH2 was more harmful than PS and PS-COOH. Exposure to the nanoparticle complex with MH resulted in a decrease in hatching rate, an increase in mortality, developmental abnormalities, an increase in reactive oxygen species, catalase, and lipid peroxidase, and a decrease in total protein and superoxide dismutase, indicating a synergistic effect. There were no significant differences between the complex and the individual nanoparticles. However, accumulating these particles in organisms could contaminate the food chain. These results highlight the potential environmental risks associated with the simultaneous exposure of aquatic species to plastics, particularly smaller PS, aminated PS, and pharmaceutical complex PS.

Effects of metformin on wild fathead minnows (Pimephales promelas) using in-lake mesocosms in a boreal lake ecosystem

Due to its widespread use for the treatment of Type-2 diabetes, metformin is routinely detected in surface waters globally. Laboratory studies have shown that environmentally relevant concentrations of metformin can adversely affect the health of adult fish, with effects observed more frequently in males. However, the potential risk to wild fish populations has yet to be fully elucidated and remains a topic of debate. To explore whether environmentally relevant metformin exposure poses a risk to wild fish populations, the present study exposed wild fathead minnows (Pimephales promelas) to 5 or 50 μg/L metformin via 2 m diameter in-lake mesocosms deployed in a natural boreal lake in Northern Ontario at the International Institute for Sustainable Development - Experimental Lakes Area (IISD-ELA). Environmental monitoring was performed at regular intervals for 8-weeks, with fish length, weight (body, liver and gonad), condition factor, gonadosomatic index, liver-somatic index, body composition (water and biomolecules) and hematocrit levels evaluated at test termination. Metabolic endpoints were also evaluated using liver, brain and muscle tissue, and gonads were evaluated histologically. Results indicate that current environmental exposure scenarios may be sufficient to adversely impact the health of wild fish populations. Adult male fish exposed to metformin had significantly reduced whole body weight and condition factor and several male fish from the high-dose metformin had oocytes in their testes. Metformin-exposed fish had altered moisture and lipid (decrease) content in their tissues. Further, brain (increase) and liver (decrease) glycogen were altered in fish exposed to high-dose metformin. To our knowledge, this study constitutes the first effort to understand metformin's effects on a wild small-bodied fish population under environmentally relevant field exposure conditions.

Erythrocyte alterations in specimens of Danio rerio caused by exposure to metformin

The antidiabetic drug metformin is widely prescribed around the world. However, its permanence in different environmental concentrations has been associated with adverse toxicological effects in organisms that do not target its therapeutic action. In the aquatic environment, fish such as the Zebrafish (Danio rerio) have been considered potential bioindicators of environmental impacts and used as experimental models in toxicological studies due to the sensitivity of these species to different types of contaminants, including pharmaceuticals. Thus, this study aimed to analyze metformin's cytotoxic effects on Danio rerio erythrocytes. The animals were submitted to different concentrations of the drug (50 µg/L, 100 µg/L, 150 µg/L, and 10000 µg/L) for 365 days and subsequently observed employing light microscopy and scanning electron microscopy (SEM) to evaluate the alterations that occurred. Exposure of animals to metformin led to significant erythrocyte cell abnormalities across all tested concentrations, with a particularly pronounced effect at the higher concentration previously defined as the NOEC (No Observed Effect Concentration). Remarkable abnormalities included cytoplasmic vacuoles, echinocytes, and vesicle-like cytoplasmic fragments. These findings suggest that metformin, even at concentrations similar to those found in nature and at the NOEC level, exhibits cytotoxic potential in D. rerio, raising concerns about its potential health impacts.

Summary recommendations on "Analytical methods for substances in the Watch List under the Water Framework Directive"

The Watch List (WL) is a monitoring program under the European Water Framework Directive (WFD) to obtain high-quality Union-wide monitoring data on potential water pollutants for which scarce monitoring data or data of insufficient quality are available. The main purpose of the WL data collection is to determine if the substances pose a risk to the aquatic environment at EU level and subsequently to decide whether a threshold, the Environmental Quality Standards (EQS) should be set for them and, potentially to be listed as priority substance in the WFD. The first WL was established in 2015 and contained 10 individual or groups of substances while the 4th WL was launched in 2022. The results of monitoring the substances of the first WL showed that some countries had difficulties to reach an analytical Limit of Quantification (LOQ) below or equal to the Predicted No-Effect Concentrations (PNEC) or EQS. The Joint Research Centre (JRC) of the European Commission (EC) organised a series of workshops to support the EU Member States (MS) and their activities under the WFD. Sharing the knowledge among the Member States on the analytical methods is important to deliver good data quality. The outcome and the discussion engaged with the experts are described in this paper, and in addition a literature review of the most important publications on the analysis of 17-alpha-ethinylestradiol (EE2), amoxicillin, ciprofloxacin, metaflumizone, fipronil, metformin, and guanylurea from the last years is presented.

Journey of micronanoplastics with blood components

The entry of micro- and nanoplastics (MNPs) into the human body is inevitable. They enter blood circulation through ingestion, inhalation, and dermal contact by crossing the gut-lung-skin barrier (the epithelium of the digestive tract, the respiratory tract, and the cutaneous layer). There are many reports on their toxicities to organs and tissues. This paper presents the first thorough assessment of MNP-driven bloodstream toxicity and the mechanism of toxicity from the viewpoint of both MNP and environmental co-pollutant complexes. Toxic impacts include plasma protein denaturation, hemolysis, reduced immunity, thrombosis, blood coagulation, and vascular endothelial damage, among others, which can lead to life-threatening diseases. Protein corona formation, oxidative stress, cytokine alterations, inflammation, and cyto- and genotoxicity are the key mechanisms involved in toxicity. MNPs change the secondary structure of plasma proteins, thereby preventing their transport functions (for nutrients, drugs, oxygen, etc.). MNPs inhibit erythropoiesis by influencing hematopoietic stem cell proliferation and differentiation. They cause red blood cell and platelet aggregation, as well as increased adherence to endothelial cells, which can lead to thrombosis and cardiovascular disease. White blood cells and immune cells phagocytose MNPs, provoking inflammation. However, research gaps still exist, including gaps regarding the combined toxicity of MNPs and co-pollutants, toxicological studies in human models, advanced methodologies for toxicity analysis, bioaccumulation studies, inflammation and immunological responses, dose-response relationships of MNPs, and the effect of different physiochemical characteristics of MNPs. Furthermore, most studies have analyzed toxicity using prepared MNPs; hence, studies must be undertaken using true-to-life MNPs to determine the real-world scenario. Additionally, nanoplastics may further degrade into monomers, whose toxic effects have not yet been explored. The research gaps highlighted in this review will inspire future studies on the toxicity of MNPs in the vascular/circulatory systems utilizing in vivo models to enable more reliable health risk assessment.

Interaction of antidiabetic formulation with nanoplastics and its binary influence on plasma protein

Nanoplastics exposure to humans becomes inevitable due to its prevalence and permanence. Adsorption of emerging pollutant metformin hydrochloride (Met-HCl) -antidiabetic drug, on polystyrene nanoplastics (PSNPs) and influence on plasma protein binding was investigated. Fluorescence studies were carried out for human serum albumin (HSA) binding. Adsorption follows pseudo-second-order kinetics, intraparticle-diffusion, and Langmuir isotherm, undergoing both physisorption and chemisorption which was validated by FE-SEM, FTIR, and HRMS measurements. Complex, experiences static quenching mechanism by hydrogen bonding and VanderWaals force of attraction to HSA. FTIR confirms the secondary structural alteration of HSA. Since Met-HCl covers the NPs' surface, NPs' affinity for HSA is reduced and they might reach the target organs of Met-HCl, disrupt antidiabetic mechanisms and cause far-reaching implications. Results from molecular docking and simulation studies backed up these results as hydrophobic and hydrogen bonds dominate the binding process of the HSA-Met-HCl-PSNPs complex. This work will aid in understanding of the toxico-kinetics/dynamics of binary contaminants.

Metformin: A Review of Potential Mechanism and Therapeutic Utility Beyond Diabetes

Metformin has been designated as one of the most crucial first-line therapeutic agents in the management of type 2 diabetes mellitus. Primarily being an antihyperglycemic agent, metformin also has a plethora of pleiotropic effects on various systems and processes. It acts majorly by activating AMPK (Adenosine Monophosphate-Activated Protein Kinase) in the cells and reducing glucose output from the liver. It also decreases advanced glycation end products and reactive oxygen species production in the endothelium apart from regulating the glucose and lipid metabolism in the cardiomyocytes, hence minimizing the cardiovascular risks. Its anticancer, antiproliferative and apoptosis-inducing effects on malignant cells might prove instrumental in the malignancy of organs like the breast, kidney, brain, ovary, lung, and endometrium. Preclinical studies have also shown some evidence of metformin's neuroprotective role in Parkinson's disease, Alzheimer's disease, multiple sclerosis and Huntington's disease. Metformin exerts its pleiotropic effects through varied pathways of intracellular signalling and exact mechanism in the majority of them remains yet to be clearly defined. This article has extensively reviewed the therapeutic benefits of metformin and the details of its mechanism for a molecule of boon in various conditions like diabetes, prediabetes, obesity, polycystic ovarian disease, metabolic derangement in HIV, various cancers and aging.

Evaluation of Complex Mixture Toxicity in the Milwaukee Estuary (WI, USA) Using Whole-Mixture and Component-Based Evaluation Methods

Anthropogenic activities introduce complex mixtures into aquatic environments, necessitating mixture toxicity evaluation during risk assessment. There are many alternative approaches that can be used to complement traditional techniques for mixture assessment. Our study aimed to demonstrate how these approaches could be employed for mixture evaluation in a target watershed. Evaluations were carried out over 2 years (2017-2018) across 8-11 study sites in the Milwaukee Estuary (WI, USA). Whole mixtures were evaluated on a site-specific basis by deploying caged fathead minnows (Pimephales promelas) alongside composite samplers for 96 h and characterizing chemical composition, in vitro bioactivity of collected water samples, and in vivo effects in whole organisms. Chemicals were grouped based on structure/mode of action, bioactivity, and pharmacological activity. Priority chemicals and mixtures were identified based on their relative contributions to estimated mixture pressure (based on cumulative toxic units) and via predictive assessments (random forest regression). Whole mixture assessments identified target sites for further evaluation including two sites targeted for industrial/urban chemical mixture effects assessment; three target sites for pharmaceutical mixture effects assessment; three target sites for further mixture characterization; and three low-priority sites. Analyses identified 14 mixtures and 16 chemicals that significantly contributed to cumulative effects, representing high or medium priority targets for further ecotoxicological evaluation, monitoring, or regulatory assessment. Overall, our study represents an important complement to single-chemical prioritizations, providing a comprehensive evaluation of the cumulative effects of mixtures detected in a target watershed. Furthermore, it demonstrates how different tools and techniques can be used to identify diverse facets of mixture risk and highlights strategies that can be considered in future complex mixture assessments. Environ Toxicol Chem 2023;42:1229-1256. © 2023 SETAC.

The impact of pharmaceutical pollutants on daphnids - A metabolomic approach

Pharmaceuticals have been classified as emerging contaminants in the aquatic ecosystem, mainly due to their increased use and improper disposal. A significant range of pharmaceutical compounds and their metabolites have been globally detected in surface waters and pose detrimental effects to non-target organisms. Monitoring pharmaceutical water pollution relies on the analytical approaches for their detection, however, such approaches are limited by their sensitivity limit and coverage of the wide range pharmaceutical compounds. This lack of realism in risk assessment is bypassed with effect-based methods, which are complemented by chemical screening and impact modelling, and are able to provide mechanistic insight for pollution. Focusing on the freshwater ecosystem, in this study we evaluated the acute effects on daphnids for three distinct groups of pharmaceuticals; antibiotics, estrogens, and a range of commonly encountered environmentally relevant pharmaceutical pollutants. Combining several endpoints such as mortality, biochemical (enzyme activities) and holistic (metabolomics) we discovered distinct patterns in biological responses. In this study, changes in enzymes of metabolism e.g. phosphatases and lipase, as well as the detoxification enzyme, glutathione-S-transferase, were recorded following acute exposure to the selected pharmaceuticals. A targeted analysis of the hydrophilic profile of daphnids revealed mainly the up-regulation of metabolites following metformin, gabapentin, amoxicillin, trimethoprim and β-estradiol. Whereas gemfibrozil, sulfamethoxazole and oestrone exposure resulted in the down-regulation of majority of metabolites.

A forecast effects of climate change and anthropogenic compounds in Gambusia holbrooki: ecotoxicological effects of salinity and metformin

Due to global warming and extreme weather events, estuarine and coastal ecosystems are facing sudden fluctuations in salinity. These ecosystems are also threatened by organic and inorganic compounds that increase water pollution. Metformin is an antidiabetic drug commonly used by patients with type-2 diabetes, and an increase in environmental concentration has been recorded. To better understand the impacts of these two stressors on aquatic organisms, this study assessed: 1) the acute (96 h) ecotoxicological effects (antioxidant and biotransformation capacity, oxidative damage, energetic reserves, and protein content, neurotoxicity) induced by a range of metformin concentrations in Gambusia holbrooki under different salinities (17, 24, 31 expressed as Practical Salinity Units - PSU); and 2) the same endpoints after chronic exposure (28 d) under a range of metformin concentrations at a salinity of 17. The results obtained from the acute exposure showed interactions between salinity and metformin in G. holbrooki superoxide dismutase (SOD) activity, body protein, and glycogen (GLY) contents. The results revealed that an increase in salinity can modulate the response of G. holbrooki to metformin. Chronically exposed organisms showed that metformin led to a significant decrease in SOD activity at most of the tested concentrations (0.5, 1.0, and 10 µg/L). In addition, glutathione S-transferases increased and glutathione peroxidase activity decreased significantly at concentrations of metformin of 5 and 10 at the µg/L, respectively. Therefore, overall, metformin can lead to potential oxidative stress in G. holbrooki the highest metformin concentrations tested and the GLY content in G. holbrooki increased after exposure to metformin concentrations of 0.5, 1.0 and 5.0 μg/L. Published studies have already shown that metformin alone can lead to oxidative damage in aquatic species, endangering the biodiversity of aquatic ecosystems. Therefore, additional ecotoxicological studies should be performed to characterize if other metformin concentrations combined with salinity, or other climate change-related factors, might impact non-target species. Standard toxicity bioassays may not be predictive of actual pollutants (e.g. metformin) toxicity under variable environmental conditions, and the investigation of a wider range of exposure conditions could improve the accuracy of chemical risk assessments.

Molecular Responses of Daphnids to Chronic Exposures to Pharmaceuticals

Pharmaceutical compounds are among several classes of contaminants of emerging concern, such as pesticides, heavy metals and personal care products, all of which are a major concern for aquatic ecosystems. The hazards posed by the presence of pharmaceutical is one which affects both freshwater organisms and human health-via non-target effects and by the contamination of drinking water sources. The molecular and phenotypic alterations of five pharmaceuticals which are commonly present in the aquatic environment were explored in daphnids under chronic exposures. Markers of physiology such as enzyme activities were combined with metabolic perturbations to assess the impact of metformin, diclofenac, gabapentin, carbamazepine and gemfibrozil on daphnids. Enzyme activity of markers of physiology included phosphatases, lipase, peptidase, β-galactosidase, lactate dehydrogenase, glutathione-S-transferase and glutathione reductase activities. Furthermore, targeted LC-MS/MS analysis focusing on glycolysis, the pentose phosphate pathway and the TCA cycle intermediates was performed to assess metabolic alterations. Exposure to pharmaceuticals resulted in the changes in activity for several enzymes of metabolism and the detoxification enzyme glutathione-S-transferase. Metabolic perturbations on key pathways revealed distinct groups and metabolic fingerprints for the different exposures and their mixtures. Chronic exposure to pharmaceuticals at low concentrations revealed significant alterations of metabolic and physiological endpoints.

Are Fish Populations at Risk? Metformin Disrupts Zebrafish Development and Reproductive Processes at Chronic Environmentally Relevant Concentrations

The antidiabetic drug Metformin (MET), one of the most prevalent pharmaceuticals in the environment, is currently detected in surface waters in the range of ng/L to low μg/L. As current knowledge regarding the long-term effects of environmentally relevant concentrations of MET in nontarget organisms is limited, the present study aimed at investigating the generational effects of MET, in concentrations ranging from 390 to 14 423 ng/L in the model organism Danio rerio (up to 9 mpf), including the effects on its nonexposed offspring (until 60 dpf). We integrate several apical end points, i.e., embryonic development, survival, growth, and reproduction, with qRT-PCR and RNA-seq analyses to provide additional insights into the mode of action of MET. Reproductive-related parameters in the first generation were particularly sensitive to MET. MET parental exposure impacted critical molecular processes involved in the metabolism of zebrafish males, which in turn affected steroid hormone biosynthesis and upregulated male vtg1 expression by 99.78- to 155.47-fold at 390 and 14 432 MET treatment, respectively, pointing to an estrogenic effect. These findings can potentially explain the significant decrease in the fertilization rate and the increase of unactivated eggs. Nonexposed offspring was also affected by parental MET exposure, impacting its survival and growth. Altogether, these results suggest that MET, at environmentally relevant concentrations, severely affects several biological processes in zebrafish, supporting the urgent need to revise the proposed Predicted No-Effect Concentration (PNEC) and the Environmental Quality Standard (EQS) for MET.

Sensitive and Specific Detection of Estrogens Featuring Doped Silicon Nanowire Arrays

Estrogens and estrogen-mimicking compounds in the aquatic environment are known to cause negative impacts to both ecosystems and human health. In this initial proof-of-principle study, we developed a novel vertically oriented silicon nanowire (vSiNW) array-based biosensor for low-cost, highly sensitive and selective detection of estrogens. The vSiNW arrays were formed using an inexpensive and scalable metal-assisted chemical etching (MACE) process. A vSiNW array-based p-n junction diode (vSiNW-diode) transducer design for the biosensor was used and functionalized via 3-aminopropyltriethoxysilane (APTES)-based silane chemistry to bond estrogen receptor-alpha (ER-α) to the surface of the vSiNWs. Following receptor conjugation, the biosensors were exposed to increasing concentrations of estradiol (E2), resulting in a well-calibrated sensor response (R ² ≥ 0.84, 1-100 ng/mL concentration range). Fluorescence measurements quantified the distribution of estrogen receptors across the vSiNW array compared to planar Si, indicating an average of 7 times higher receptor presence on the vSiNW array surface. We tested the biosensor's target selectivity by comparing it to another estrogen (estrone [E1]) and an androgen (testosterone), where we measured a high positive electrical biosensor response after E1 exposure and a minimal response after testosterone. The regeneration capacity of the biosensor was tested following three successive rinses with phosphate buffer solution (PBS) between hormone exposure. Traditional horizontally oriented Si NW field effect transistor (hSiNW-FET)-based biosensors report electrical current changes at the nanoampere (nA) level that require bulky and expensive measurement equipment making them unsuitable for field measurements, whereas the reported vSiNW-diode biosensor exhibits current changes in the microampere (μA) range, demonstrating up to 100-fold electrical signal amplification, thus enabling sensor signal measurement using inexpensive electronics. The highly sensitive and specific vSiNW-diode biosensor developed here will enable the creation of low-cost, portable, field-deployable biosensors that can detect estrogenic compounds in waterways in real-time.

A case study: temporal trends of environmental stressors and reproductive health of smallmouth bass (Micropterus dolomieu) from a site in the Potomac River Watershed, Maryland, USA

Decades of poor reproductive success and young-of-the-year survival, combined with adult mortality events, have led to a decline in the smallmouth bass (SMB; Micropterus dolomieu) population in sections of the Potomac River. Previous studies have identified numerous biologic and environmental stressors associated with negative effects on SMB health. To better understand the impact of these stressors, this study was conducted at the confluence of Antietam Creek and the Potomac River from 2013 to 2019 to identify temporal changes associated with SMB reproductive health. Surface water samples were collected and analyzed for over 300 organic contaminants, including pesticides, phytoestrogens, pharmaceuticals, hormones and total estrogenicity (E2Eq). Adult SMB were collected and sampled for multiple endpoints, including gene transcripts associated with reproduction (molecular), histopathology (cellular), and organosomatic indices (tissue). In males, biomarkers of estrogenic endocrine disruption, including testicular oocytes (TO) and plasma vitellogenin (Vtg) were assessed. Numerous agriculture-related contaminants or land use patterns were associated with gene transcript abundance in both male and female SMB. Positive associations between pesticides in the immediate catchment with TO severity and E2Eq with plasma Vtg in males were identified. In males, the prevalence of TO and detectable levels of plasma Vtg, liver vitellogenin transcripts (vtg) and testis vtg were high throughout the study. Peaks of complex mixtures of numerous contaminants occurred during the spring/early summer when spawning and early development occurs and to a lesser extent in fall/winter during recrudescence. Management practices to reduce exposure during these critical and sensitive periods may enhance reproductive health of these economically important sportfishes.

Acute and chronic ecotoxicological effects of pharmaceuticals and their mixtures in Daphnia similis

Pharmaceuticals have increasingly received attention from the scientific community due to their growing intake, improved detection and potential ecological risks. Several pharmaceuticals, including antidepressants, anti-inflammatory and antidiabetic compounds and antibiotics, have been described as contaminants in different water matrices. In this context, the aim of the present study was to assess the acute and chronic effects of four classes of pharmaceuticals (acetylsalicylic acid, fluoxetine, metformin and ciprofloxacin) individually and in binary and quartenary mixture. Furthermore, the toxicity of binary mixtures containing the antidepressant fluoxetine was also evaluated. The results of the single acute and chronic toxicity assays indicate lower acetylsalicylic acid and higher fluoxetine toxicity towards Daphnia similis. Regarding the evaluated mixture toxicity, the nature of potential toxicological interactions was predicted by applying mathematical concentration addition and independent action models. The findings revealed both antagonistic and synergistic features, depending on the applied amounts and doses. Finally, the chronic assays performed with the quaternary mixture indicated the presence of a hormetic effect at low concentrations. In sum, the present study demonstrated that the effects of individual pharmaceuticals can underestimate the risk level of these contaminants in the environment.

Microplastics in urban waters and its effects on microbial communities: a critical review

Microplastic (MP) pollution is one of the emerging threats to the water and terrestrial environment, forcing a new environmental challenge due to the growing trend of plastic released into the environment. Synthetic and non-synthetic plastic components can be found in rivers, lakes/reservoirs, oceans, mountains, and even remote areas, such as the Arctic and Antarctic ice sheets. MPs' main challenge is identifying, measuring, and evaluating their impacts on environmental behaviors, such as carbon and nutrient cycles, water and wastewater microbiome, and the associated side effects. However, until now, no standardized methodical protocols have been proposed for comparing the results of studies in different environments, especially in urban water and wastewater. This review briefly discusses MPs' sources, fate, and transport in urban waters and explains methodological uncertainty. The effects of MPs on urban water microbiomes, including urban runoff, sewage wastewater, stagnant water in plumbing networks, etc., are also examined in depth. Furthermore, this study highlights the pathway of MPs and their transport vectors to different parts of ecosystems and human life, particularly through mediating microbial communities, antibiotic-resistant genes, and biogeochemical cycles. Overall, we have briefly highlighted the present research gaps, the lack of appropriate policy for evaluating microplastics and their interactions with urban water microbiomes, and possible future initiatives.

Chronic exposure to realistic concentrations of metformin prompts a neurotoxic response in Danio rerio adults

Metformin (MET) is among the most consumed drugs around the world, and thus, it is considered the uppermost drug in mass discharged into water settings. Nonetheless, data about the deleterious consequences of MET on water organisms are still scarce and require further investigation. Herein, we aimed to establish whether or not chronic exposure to MET (1, 20, and 40 μg/L) may alter the swimming behavior and induce neurotoxicity in Danio rerio adults. After 4 months of exposure, MET-exposed fish exhibited less swimming activity when compared to control fish. Moreover, compared with the control group, MET significantly inhibited the activity of AChE and induced oxidative damage in the brain of fish. Concerning gene expression, MET significantly upregulated the expression of Nrf1, Nrf2, BAX, p53, BACE1, APP, PSEN1, and downregulated CASP3 and CASP9. Although MET did not overexpress the CASP3 gene, we saw a meaningful rise in the activity of this enzyme in the blood of fish exposed to MET compared to the control group, which we then confirmed by a high number of apoptotic cells in the TUNEL assay. Our findings demonstrate that chronic exposure to MET may impair fish swimming behavior, making them more vulnerable to predators.

Effects of Metformin and its Metabolite Guanylurea on Fathead Minnow (Pimephales promelas) Reproduction

Metformin, along with its biotransformation product guanylurea, is commonly observed in municipal wastewaters and subsequent surface waters. Previous studies in fish have identified metformin as a potential endocrine-active compound, but there are inconsistencies with regard to its effects. To further investigate the potential reproductive toxicity of metformin and guanylurea to fish, a series of experiments was performed with adult fathead minnows (Pimephales promelas). First, explants of fathead minnow ovary tissue were exposed to 0.001-100 µM metformin or guanylurea to investigate whether the compounds could directly perturb steroidogenesis. Second, spawning pairs of fathead minnows were exposed to metformin (0.41, 4.1, and 41 µg/L) or guanylurea (1.0, 10, and 100 µg/L) for 23 days to assess impacts on reproduction. Lastly, male fathead minnows were exposed to 41 µg/L metformin, 100 µg/L guanylurea, or a mixture of both compounds, with samples collected over a 96-h time course to investigate potential impacts to the hepatic transcriptome or metabolome. Neither metformin nor guanylurea affected steroid production by ovary tissue exposed ex vivo. In the 23 days of exposure, neither compound significantly impacted transcription of endocrine-related genes in male liver or gonad, circulating steroid concentrations in either sex, or fecundity of spawning pairs. In the 96-h time course, 100 µg guanylurea/L elicited more differentially expressed genes than 41 µg metformin/L and showed the greatest impacts at 96 h. Hepatic transcriptome and metabolome changes were chemical- and time-dependent, with the largest impact on the metabolome observed at 23 days of exposure to 100 µg guanylurea/L. Overall, metformin and guanylurea did not elicit effects consistent with reproductive toxicity in adult fathead minnows at environmentally relevant concentrations. Environ Toxicol Chem 2022;41:2708-2720. © 2022 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

The Effects of Single and Combined Stressors on Daphnids-Enzyme Markers of Physiology and Metabolomics Validate the Impact of Pollution

The continuous global increase in population and consumption of resources due to human activities has had a significant impact on the environment. Therefore, assessment of environmental exposure to toxic chemicals as well as their impact on biological systems is of significant importance. Freshwater systems are currently under threat and monitored; however, current methods for pollution assessment can neither provide mechanistic insight nor predict adverse effects from complex pollution. Using daphnids as a bioindicator, we assessed the impact in acute exposures of eight individual chemicals and specifically two metals, four pharmaceuticals, a pesticide and a stimulant, and their composite mixture combining phenotypic, biochemical and metabolic markers of physiology. Toxicity levels were in the same order of magnitude and significantly enhanced in the composite mixture. Results from individual chemicals showed distinct biochemical responses for key enzyme activities such as phosphatases, lipase, peptidase, β-galactosidase and glutathione-S-transferase. Following this, a more realistic mixture scenario was assessed with the aforementioned enzyme markers and a metabolomic approach. A clear dose-dependent effect for the composite mixture was validated with enzyme markers of physiology, and the metabolomic analysis verified the effects observed, thus providing a sensitive metrics in metabolite perturbations. Our study highlights that sensitive enzyme markers can be used in advance on the design of metabolic and holistic assays to guide the selection of chemicals and the trajectory of the study, while providing mechanistic insight. In the future this could prove to become a useful tool for understanding and predicting freshwater pollution.

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.

Metformin as an emerging concern in wastewater: Occurrence, analysis and treatment methods

Metformin is a wonder drug used as an anti-hypoglycemic medication; it is also used as a cancer suppression medicament. Metformin is a first line of drug choice used by doctors for patients with type 2 diabetes. It is used worldwide where the drug's application varies from an anti-hypoglycemic medication to cancer oppression and as a weight loss treatment drug. Due to its wide range of usage, metformin and its byproducts are found in waste water and receiving aquatic environment. This leads to the accumulation of metformin in living beings and the environment where excess concentration levels can lead to ailments such as lactic acidosis or vitamin B12 deficiency. This drug could become of future water treatment concerns with its tons of production per year and vast usage. As a result of continuous occurrence of metformin has demanded the need of implementing and adopting different strategies to save the aquatic systems and the exposure to metformin. This review discuss the various methods for the elimination of metformin from wastewater. Along with that, the properties, occurrence, and health and environmental impacts of metformin are addressed. The different analytical methods for the detection of metformin are also explained. The main findings are discussed with respect to the management of metformin as an emerging contaminants and the major recommendations are discussed to understand the major research gaps.

Environmentally relevant concentration of caffeine-effect on activity and circadian rhythm in wild perch

We studied the ecological consequences of widespread caffeine contamination by conducting an experiment focused on changes in the behavioral traits of wild perch (Perca fluviatilis) after waterborne exposure to 10 μg L^-1 of caffeine. We monitored fish swimming performance during both light and dark conditions to study the effect of caffeine on fish activity and circadian rhythm, using a novel three-dimensional tracking system that enabled positioning even in complete darkness. All individuals underwent three behavioral trials-before exposure, after 24 h of exposure, and after 5 days of exposure. We did not observe any effect of the given caffeine concentration on fish activity under light or dark conditions. Regardless of caffeine exposure, fish swimming performance was significantly affected by both the light-dark conditions and repeating of behavioral trials. Individuals in both treatments swam significantly more during the light condition and their activity increased with time as follows: before exposure < after 24 h of exposure < after 5 days of exposure. We confirmed that the three-dimensional automated tracking system based on infrared sensors was highly effective for conducting behavioral experiments under completely dark conditions.

Comparative Effects of Embryonic Metformin Exposure on Wild and Laboratory-Spawned Fathead Minnow (Pimephales promelas) Populations

Metformin is routinely detected in aquatic ecosystems because of its widespread use as a treatment for Type 2 diabetes. Laboratory studies have shown that exposure to environmentally relevant concentrations of metformin can alter metabolic pathways and impact the growth of early life stage (ELS) fish; however, it is unknown whether these effects occur in wild populations. Herein, we evaluate whether findings from laboratory studies are representative and describe the relative sensitivities of both populations. Duplicate exposures (0, 5, or 50 μg/L metformin) were conducted using wild- and lab-spawned fathead minnow (Pimephales promelas) embryos. Apart from the water source, exposure conditions remained constant. Wild embryos were exposed to previously dosed lake water to account for changes in bioavailability, while reconstituted freshwater was used for the laboratory study. Developmental metformin exposure differentially impacted the growth and morphology of both cohorts, with energy dyshomeostasis and visual effects indicated. The fitness of wild-spawned larvae was impacted to a greater extent relative to lab-spawned fish. Moreover, baseline data reveal important morphological differences between wild- and lab-spawned ELS fatheads that may diminish representativeness of lab studies. Findings also confirm the bioavailability of metformin in naturally occurring systems and suggest current exposure scenarios may be sufficient to negatively impact developing fish.

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.

Hypothesis: Metformin is a potential reproductive toxicant

Metformin is the first-line oral treatment for type 2 diabetes mellitus and is prescribed to more than 150 million people worldwide. Metformin's effect as a glucose-lowering drug is well documented but the precise mechanism of action is unknown. A recent finding of an association between paternal metformin treatment and increased numbers of genital birth defects in sons and a tendency towards a skewed secondary sex ratio with less male offspring prompted us to focus on other evidence of reproductive side effects of this drug. Metformin in humans is documented to reduce the circulating level of testosterone in both men and women. In experimental animal models, metformin exposure in utero induced sex-specific reproductive changes in adult rat male offspring with reduced fertility manifested as a 30% decrease in litter size and metformin exposure to fish, induced intersex documented in testicular tissue. Metformin is excreted unchanged into urine and feces and is present in wastewater and even in the effluent of wastewater treatment plants from where it spreads to rivers, lakes, and drinking water. It is documented to be present in numerous freshwater samples throughout the world - and even in drinking water. We here present the hypothesis that metformin needs to be considered a potential reproductive toxicant for humans, and probably also for wildlife. There is an urgent need for studies exploring the association between metformin exposure and reproductive outcomes in humans, experimental animals, and aquatic wildlife.

Does aquatic sediment pollution result in contaminated food sources?

The sediment pollution of the aquatic environment by waste due to anthropogenic activity is of an increasing concern. The contaminants coming from the aquatic environment can enter the aquatic food chain and accumulate in the tissues of fish and shellfish used for human consumption. The aim of this study was to sum up the current level of knowledge concerning the pollution of aquatic sediments and its transfer to aquatic foods as well as to indicate whether such contamination has the potential to affect the health and welfare of aquatic organisms as well as the quality and safety of the species intended for human consumption. Based on the results of scientific studies, the European Food Safety Authority, and the Rapid Alert System for Food and Feed, contamination of fish and seafood occurs predominantly through their diet and the levels of bioaccumulative contaminants are higher in fish which rank higher in the food chain. Contamination of aquatic habitats can not only significantly affect behavior, development, and welfare of aquatic organisms, but it can also affect the safety of fish and seafood for human consumption.

Oxidative stress as a potential mechanism by which guanylurea disrupts the embryogenesis of Danio rerio

Metformin is one the most prescribed drug to treat type 2 diabetes. In wastewater treatment plants, this drug is bacterially transformed to guanylurea, which occurs at higher concentrations in the aquatic environments than its parent compound. Since there is a huge knowledge gap about the toxicity of this metabolite on aquatic organisms, we aimed to investigate the impact of guanylurea on the embryonic development and oxidative stress biomarkers of zebrafish (Danio rerio). For this effect, zebrafish embryos (4 h post fertilization) were exposed to 25, 50, 100, 200, 250, 25,000, 50,000, 75,000 μg/L guanylurea until 96 h post fertilization. Guanylurea led to a significant delay in the hatching process in all exposure groups. Furthermore, this transformation product affected the embryonic development of fish, inducing severe body alterations and consequently leading to their death. The most pronounced malformations were malformation of tail, scoliosis, pericardial edema, yolk deformation and craniofacial malformation. Concerning oxidative stress response, we demonstrated that guanylurea induced the antioxidant activity of superoxide dismutase, catalase, and glutathione peroxidase in zebrafish embryos. In addition, the levels of lipid peroxidation, protein carbonyl and hydroperoxide content were also increased in the embryos exposed to this transformation product. However, the integrated biomarker response (IBR) analysis carried out in this study demonstrated that oxidative damage biomarkers got more influence over the embryos than antioxidant enzymes. Thus, we can conclude that guanylurea induces oxidative stress in zebrafish embryos, and that this transformation product impair the normal development of this freshwater organism.

Antidiabetic drug metformin disrupts the embryogenesis in zebrafish through an oxidative stress mechanism

In recent years, the consumption of metformin has increased not only due to the higher prevalence of type 2 diabetes, but also due to their usage for other indications such as cancer and polycystic ovary syndrome. Consequently, metformin is currently among the highest drug by weight released into the aquatic environments. Since the toxic effects of this drug on aquatic species has been scarcely explored, the aim of this work was to investigate the influence of metformin on the development and redox balance of zebrafish (Danio rerio) embryos. For this purpose, zebrafish embryos (4 hpf) were exposed to 1, 10, 20, 30, 40, 50, 75 and 100 μg/L metformin until 96 hpf. Metformin significantly accelerated the hatching process in all exposure groups. Moreover, this drug induced several morphological alterations on the embryos, affecting their integrity and consequently leading to their death. The most frequent malformations found on the embryos included malformation of tail, scoliosis, pericardial edema and yolk deformation. Regarding oxidative balance, metformin significantly induced the activity of antioxidant enzymes and the levels of oxidative damage biomarkers. However, our IBR analisis demonstrated that oxidative damage biomarkers got more influence over the embryos. Together these results demonstrated that metformin may affect the embryonic development of zebrafish and that oxidative stress may be involved in the generation of this embryotoxic process.

Coral Ecotoxicological Data Evaluation for the Environmental Safety Assessment of Ultraviolet Filters

There is growing interest in the environmental safety of ultraviolet (UV) filters found in cosmetic and personal care products (CPCPs). The CPCP industry is assessing appropriate environmental risk assessment (ERA) methods to conduct robust environmental safety assessments for these ingredients. Relevant and reliable data are needed for ERA, particularly when the assessment is supporting regulatory decision-making. In the present study, we apply a data evaluation approach to incorporate nonstandard toxicity data into the ERA process through an expanded range of reliability scores over commonly used approaches (e.g., Klimisch scores). The method employs an upfront screening followed by a data quality assessment based largely on the Criteria for Reporting and Evaluating Ecotoxicity Data (CRED) approach. The method was applied in a coral case study in which UV filter toxicity data was evaluated to identify data points potentially suitable for higher tier and/or regulatory ERA. This is an optimal case study because there are no standard coral toxicity test methods, and UV filter bans are being enacted based on findings reported in the current peer-reviewed data set. Eight studies comprising nine assays were identified; four of the assays did not pass the initial screening assessment. None of the remaining five assays received a high enough reliability score (R_n ) to be considered of decision-making quality (i.e., R1 or R2). Four assays were suitable for a preliminary ERA (i.e., R3 or R4), and one assay was not reliable (i.e., R6). These results highlight a need for higher quality coral toxicity studies, potentially through the development of standard test protocols, to generate reliable toxicity endpoints. These data can then be used for ERA to inform environmental protection and sustainability decision-making. Environ Toxicol Chem 2021;40:3441-3464. © 2021 Personal Care Products Council. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Induction of apoptosis in the gonads of Mytilus edulis by metformin and increased temperature, via regulation of HSP70, CASP8, BCL2 and FAS

Pharmaceutically active compounds have been considered contaminants of emerging concern, in response to evidence that these substances may adversely affect aquatic organisms. Here we expose mussels for 7 days to metformin, the most commonly prescribed anti-diabetes treatment, at a concentration of 40 μg/L and a high temperature of 20 °C. The apoptosis-related genes HSP70, CASP8, BCL2 and FAS showed variation in expression in gonadal tissue. The results suggest that complex interactions between these genes are modulating the onset of apoptotic changes such as atresia and follicle degeneration. The temperature induced apoptosis may be initiated by overexpression of CASP8. Conversely, metformin may induce apoptosis by suppressing the anti-apoptotic gene BCL2, thus promoting the process. Interestingly, apoptosis and follicle degeneration are likely FAS-mediated, following the synergistic effect of metformin and temperature. The potential of metformin to act as a non-traditional EDC, due to its impact on the reproductive system in mussels is discussed.

Pharmaceutical and transformation products during unplanned water reuse: Insights into natural attenuation, plant uptake and human health impact under field conditions

In urban and periurban areas, agricultural soils are often irrigated with surface water containing a complex mixture of contaminants due to wastewater treatment plant (WWTP) effluent discharges. The unplanned water reuse of these resources for crop irrigation can represent a pathway for contaminant propagation and a potential health risk due to their introduction in the food chain. The aim of this study is to provide data about the magnitude of attenuation processes and plant uptake, allowing for a reliable assessment of contaminant transfer among compartments and of the human health risk derived from unplanned water reuse activities. Target compounds are 25 pharmaceuticals, including transformation products (TPs). The field site is an agricultural parcel where maize is irrigated by a gravity-fed surface system supplied by the Jarama river, a water course strongly impacted by WWTP effluents. Throughout the 3-month irrigation period, irrigation water and water infiltrating through the vadose zone were sampled. The agricultural soil was collected before and after the irrigation campaign, and maize was sampled before harvesting. All selected compounds are detected in irrigation water (up to 12,867 ng L^-1). Metformin, two metamizole TPs and valsartan occur with the highest concentrations. For most pharmaceuticals, results demonstrate a high natural attenuation during soil infiltration (>60%). However, leached concentrations of some compounds can be still at concern level (>400 ng L^-1). A persistent behavior is observed for carbamazepine, carbamazepine epoxide and sulfamethoxazole. Pharmaceutical soil contents are in the order of ng g^-1 and positively ionized compounds accumulate more effectively. Results also indicate the presence of a constant pool of drugs in soils. Only neutral and cationic pharmaceuticals are taken up in maize tissues, mainly in the roots. There is an insignificant threat to human health derived from maize consumption however, additional toxicity tests are recommended for 4AAA and acetaminophen.

Developmental phenotypic and transcriptomic effects of exposure to nanomolar levels of metformin in zebrafish

Metformin is found in the majority of lakes and streams in the United States, leading to widespread environmental exposure. Results of the present study indicate that extended duration metformin exposure at critical developmental periods leads to decreased survival rates in zebrafish (danio rerio), an NIH approved human model. Significant abnormalities are seen with extended duration metformin exposure from 4 h post fertilization up to 5 days post fertilization, although short term metformin exposure for 24 h at 4-5 days post fertilization did not lead to any significant abnormalities. Both extended and short term duration did however have an impact on locomotor activity of zebrafish, and several genes involved in neurological and cardiovascular development were differentially expressed after exposure to metformin. The changes seen in behavior, gene expression and morphological abnormalities caused by metformin exposure should be examined further in future studies in order to assess their potential human health implications as metformin prescriptions continue to increase worldwide.

Metformin environmental exposure: A systematic review

This review discussed the occurrence, ecological impacts, and effects of metformin, a drug used for type 2 diabetes among other diseases. It is one of the most commonly found medicines in aquatic environments owing to its incomplete metabolism in the human body, and is eventually disposed in wastewater. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed as a guide. After searching various databases, 48 eligible studies were selected for the review. Metformin reportedly occurs in different environmental matrices, as measurable concentrations of metformin are found in sewage (urban and hospital), influent/sludge/effluent from wastewater treatment plants, surface water (rivers, lakes, estuaries, oceans, and non-specific sources), tap/drinking water, and sediment (lake and recipient seawaters). Data on metformin detection in aquatic environments in 14 countries were studied, but a consensus on the risk patterns of pharmaceutical products was not determined. Many studies have been conducted on different test organisms, demonstrating that metformin can drive the expression of diverse genes, particularly those responsible for endocrine hormone pathways. Chronic exposure to metformin can be tested using models and other tools to understand this field, which remains largely unexplored. Our results contribute to the current ecotoxicology knowledge related to typically used drugs and provide a basis for further investigations.

Continuous adsorptive removal of glimepiride using multi-walled carbon nanotubes in fixed-bed column

Water pollution by emerging pollutants such as pharmaceutical and personal care products is one of today's biggest challenges. The presence of these emerging contaminants in water has raised increasing concern due to their frequent appearance and persistence in the aquatic ecosystem and threat to health and safety. The antidiabetic drug glimepiride, GPD, is among these compounds, and it possesses adverse effects on human health if not carefully administered. Several conventional processes were proposed for the elimination of these persistent contaminants, and adsorption is among them. Therefore, in this study, the adsorptive removal of GPD from water using multi-walled carbon nanotubes (MWCNT) supported on silica was explored on a fixed-bed column. The effects of bed-height, solution pH, and flow rate on the adsorptive removal of GPD were investigated. The obtained adsorption parameters using Sips, Langmuir, and Freundlich models were used to investigate the continuous adsorption. The results showed that the drug removal is improved with the increasing bed height; however, it decreased with the flow rate. The effect of pH indicated that the adsorption is significantly affected and increased in acidic medium. The convection-dispersion model coupled with Freundlich isotherm was developed and used to describe the adsorption breakthrough curves. The maximum adsorption capacity (q_m) was 275.3 mg/g, and the axial dispersion coefficients were ranged between 3.5 and 9.0 × 10⁵ m²/s. The spent adsorbent was successfully regenerated at high pH by flushing with NaOH.

Evaluating the estrogenicity of an effluent-dominated river in California, USA: Comparisons of in vitro and in vivo bioassays

Estrogenically active compounds (EACs) in surface waters can disrupt the endocrine system of biota, raising concern for aquatic species. Concentrations of EACs are generally higher in effluent-dominated aquatic systems, such as California's Santa Ana River (SAR). Addressing estrogenicity of effluent-dominated waters is increasingly important due to both increasing urbanization and climate change. To this end, water samples were collected from multiple sites downstream of wastewater treatment plants (WWTPs) and intermittent points along the SAR during 2018-2019 and cell-based bioassays were used to determine estrogen receptor activity. During baseflow conditions, the highest estradiol equivalencies (EEQs) from all SAR water between summer (August and September) and fall (November) sampling events in 2018 were from Yorba Linda (EEQ = 1.36 ± 0.38 ng/L) and Prado (1.14 ± 0.13 ng/L), respectively. Water extracts in January 2019 following a major rainfall generally had higher EEQs with the highest EEQ of 10.0 ± 0.69 ng/L observed at Yorba Linda. During low flow conditions in November 2018, male Japanese medaka (Oryzias latipes) fish were exposed to SAR water to compare to cell bioassay responses and targeted analytical chemistry for 5 steroidal estrogens. Chemical-based EEQ correlations with in vitro EEQs were statistically significant. However, vitellogenin (vtg) mRNA expression in the livers of medaka exposed to SAR water was not significantly different compared to controls. These results indicate that seasonal variation and surface water runoff events influence estrogenic activity in the SAR and may induce estrogenic effects to native fish populations in wastewater-dominated streams in general.

Metformin-Induced Epigenetic Toxicity in Zebrafish: Experimental and Molecular Dynamics Simulation Studies

The increased detection of many prescription drugs in aquatic environments has heightened concerns of their potential ecotoxicological effects. In this study, the effects of metformin (MEF) exposure on tissue accumulation, gene expression, and global DNA methylation (GDM) in zebrafish were investigated. The toxic mechanism of MEF exposure was simulated by molecular dynamics (MD) to reveal any conformational changes to DNA methyltransferase 1 (DNMT1). The results showed MEF accumulation in the gills, gut, and liver of zebrafish after 30 days of exposure, and the bioaccumulation capacity was in the order of gut > liver > gills. After a 30 day recovery period, MEF could still be detected in zebrafish tissues in groups exposed to MEF concentrations ≥ 10 μg/L. Moreover, the liver was the main site of GDM, and the restoration of GDM in the liver was slower than that in the gut and gills during the recovery period. Furthermore, MEF could induce the abnormal expression of CYP3A65, GSTM1, p53, and DNMT1 genes in the liver due to the formation of hydrogen bonds between MEF and the protein residues of those genes. The MD simulation allowed for the mechanistic determination of MEF-induced three-dimensional (3D) conformational changes and changes to the catalytic activity of DNMT1.

Fathead minnow exposed to environmentally relevant concentrations of metformin for one life cycle show no adverse effects

Metformin is a glucose-lowering drug taken for diabetes. It is excreted by humans in urine and detected in municipal wastewater effluents and rivers. Fathead minnows ( Pimephales promelas) were exposed over a life cycle to measured concentrations of metformin: 3.0, 31, and 322 μg/L. No significant changes were observed in survival, maturation, growth, condition factor, or liver size. Relative ovary size of females exposed to 322 μg/L metformin was significantly larger than controls. There was no induction of vitellogenin in plasma of minnows, and gonad maturation was not statistically different from controls. The start of breeding was delayed by 9–10 d in the mid- and high metformin treatments (statistically significant only in the mid-concentration), but numbers and quality of eggs were not statistically different from controls. There were no effects of metformin on survival or growth of offspring. Exposure to metformin at environmentally relevant concentrations (i.e., 3.0 and 31 μg/L metformin) caused no adverse effects in fathead minnows exposed for a life cycle, with the exception of a delay in time to first breeding (that did not impact overall egg production). The results of the study are important to help understand whether metformin concentrations in rivers and lakes can harm fishes.

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

Effluent-dominated streams are becoming increasingly common in temperate regions and generate complex pharmaceutical mixture exposure conditions that may impact aquatic organisms via drug-drug interactions. Here, we quantified spatiotemporal pharmaceutical exposure concentrations and composition mixture dynamics during baseflow conditions at four sites in a temperate-region effluent-dominated stream (upstream, at, and progressively downstream from effluent discharge). Samples were analyzed monthly for 1 year for 109 pharmaceuticals/degradates using a comprehensive U.S. Geological Survey analytical method and biweekly for 2 years focused on 14 most common pharmaceuticals/degradates. We observed a strong chemical gradient with pharmaceuticals only sporadically detected upstream from the effluent. Seventy-four individual pharmaceuticals/degradates were detected, spanning 5 orders of magnitude from 0.28 to 13 500 ng/L, with 38 compounds detected in >50% of samples. "Biweekly" compounds represented 77 ± 8% of the overall pharmaceutical concentration. The antidiabetic drug metformin consistently had the highest concentration with limited in-stream attenuation. The antihistamine drug fexofenadine inputs were greater during warm- than cool-season conditions but also attenuated faster. Differential attenuation of individual pharmaceuticals (i.e., high = citalopram; low = metformin) contributed to complex mixture evolution along the stream reach. This research demonstrates that variable inputs over multiple years and differential in-stream attenuation of individual compounds generate evolving complex mixture exposure conditions for biota, with implications for interactive effects.

Effects of short-term exposure of paracetamol in the gonads of blue mussels Mytilus edulis

A growing body of literature suggests that pharmaceutical contamination poses an increasing risk to marine ecosystems. Paracetamol or acetaminophen is the most widely used medicine in the world and has recently been detected in seawater. Here, we present the results of 7 days' exposure of blue mussel adults to 40 ng/L, 250 ng/L and 100 μg/L of paracetamol. Histopathology shows that haemocytic infiltration is the most observed condition in the exposed mussels. The mRNA expression of VTG, V9, ER2, HSP70, CASP8, BCL2 and FAS in mussel gonads present different patterns of downregulation. VTG and CASP8 mRNA expression show downregulation in all exposed mussels, irrespective of sex. The V9, HSP70, BCL2 and FAS transcripts follow a concentration-dependent variation in gene expression and may therefore be considered good biomarker candidates. ER2 mRNA expression shows a downregulated trend, with a clearer dose-response relationship in males. In conclusion, this study suggests that paracetamol has the potential to alter the expression of several genes related to processes occurring in the reproductive system and may therefore impair reproduction in blue mussels.

Chinese physicians' attitudes toward eco-directed sustainable prescribing from the perspective of ecopharmacovigilance: a cross-sectional study

INTRODUCTION

Eco-directed sustainable prescribing (EDSP) is an effective upstream way to reduce the environmental footprints of active pharmaceutical ingredients (APIs), a kind of emerging contaminants, from the patients' excretion. EDSP is one of the key steps in the programme of ecopharmacovigilance (EPV), a drug administration route on API pollution.

OBJECTIVE

To assess the attitudes of physicians prescribing medicines regarding EDSP from the perspective of EPV.

DESIGN

A cross-sectional study conducted from March 2019 to June 2019.

SETTING

5 government general hospitals in Hubei province, China.

PARTICIPANTS

405 physicians were randomly selected and 262 valid questionnaires were obtained.

OUTCOME MEASURES

A self-developed questionnaire, which inquired about the participant characteristics, perceptions and attitudes toward API pollution, EPV and EDSP from an EPV perspective, was emailed to collect data from physicians.

RESULTS

Most physicians agreed the existence of APIs in environment, worried about the potential environmental and ecological risks of API residues, supported the effectiveness and necessity of EDSP under an EPV perspective in decreasing environmental exposure of excreted APIs, and showed their willingness to participate in the EDSP practices. Nevertheless, no respondent identified the environmental impacts as the aspects regarding medicines affecting his(her) prescription decision, none was satisfied with knowledge on EDSP and showed confidence toward EDSP. The most important barrier to the effective implementation of EDSP was identified as 'poor awareness of EDSP and EPV'. Most responding physicians (97%) reported that they held the wait-and-see or conservative attitudes towards EDSP practice. The biggest concerns in low-dose prescribing and prescribing of drugs possessing environment-friendly excretion profiles, two EDSP approaches, were the possible negative impact on therapeutic outcomes and too complicated and professional drug evaluation process, respectively.

CONCLUSIONS

Chinese physicians had positive attitudes towards EDSP from the perspective of EPV. However, their environmental consciousness during prescribing and the related education were insufficient.

Evaluating exposures of bay mussels (Mytilus trossulus) to contaminants of emerging concern through environmental sampling and hydrodynamic modeling

Bay mussels (Mytilus trossulus) were transplanted to 18 locations representing a range of potential exposures throughout Puget Sound, WA. Tissues were analyzed for over 200 organic contaminants. Results indicated the widespread exposure of marine organisms to trace levels of organic contaminants including the synthetic opioid oxycodone, present at three urban sites, and the chemotherapy drug melphalan, present at nine locations, at levels that may be of biological concern. Land-use and wastewater outfalls were evaluated as potential sources of CECs to the nearshore. Exposure to alkylphenol ethoxylates was associated with increased impervious surfaces in upland watersheds. A hydrodynamic simulation was performed using the Salish Sea Model to integrate inputs from 99 wastewater sources to Puget Sound. Predictions were consistent with concentrations of several wastewater-associated contaminants and δ¹⁵N enrichment. These results support the notion that Puget Sound nearshore biota suffer chronic exposures to a suite of contaminants from multiple sources and provide critical to focus future monitoring and management.

Occurrence, toxic effects and removal of metformin in the aquatic environments in the world: Recent trends and perspectives

Metformin (MET) is the most common drug used to treat type 2 diabetes, but also it is used as an anticancer agent and as a treatment for polycystic ovary syndrome. This drug is not metabolized in the human body, and may enter into the environment through different pathways. In wastewater treatments plants (WWTPs), this contaminant is mainly transformed to guanylurea (GUA). However, three further transformation products (TPs): (a) 2,4- diamino-1,3,5-triazine, 4-DAT; (b) 2-amino-4-methylamino-1,3,5-triazine, 2,4-AMT; and (c) methylbiguanide, MBG; have also been associated with its metabolism. MET, GUA and MBG have been found in WWTPs influents, effluents and surface waters. Furthermore, MET and GUA bioaccumulate in edible plants species, fish and mussels potentially contaminating the human food web. MET is also a potential endocrine disruptor in fish. Phytoremediation, adsorption and biodegradation have shown a high removal efficiency of MET, in laboratory. Nonetheless, these removal methods had less efficiency when tried in WWTPs. Therefore, MET and its TPs are a threat to the human being as well as to our environment. This review comprehensively discuss the (1) pathways of MET to the environment and its life-cycle, (2) occurrence of MET and its transformation products (3) removal, (4) toxic effects and (5) future trends and perspectives of possible methods of elimination in water in order to provide potential options for managing these contaminants.

Bioconcentration and behavioral effects of four benzodiazepines and their environmentally relevant mixture in wild fish

We studied the adverse effects of four benzodiazepines frequently measured in European surface waters. We evaluated bioaccumulation potential of oxazepam, bromazepam, temazepam, and clobazam in freshwater fish species - perch (Perca fluviatilis) and we conducted a series of behavioral trials to assess their potential to alter boldness, activity, and social behavior. All selected endpoints were studied individually for each target benzodiazepine and as a mixture of all tested compounds to assess possible combinatory effects. We used a three-dimensional automated tracking system to quantify the fish behavior. The four compounds bioconcentrated differently in fish muscle (temazepam > clobazam > oxazepam > bromazepam) at high exposure (9.1, 6.9, 5.7, 8.1 µg L^-1, respectively) and low exposure (0.5, 0.5, 0.3, 0.4 µg L^-1, respectively) concentrations. A significant amount of oxazepam was also measured in fish exposed to temazepam, most likely because of the metabolic transformation of temazepam within the fish. Bromazepam, temazepam, and clobazam significantly affected fish behavior at high concentration, while no statistically significant changes were registered for oxazepam. The studied benzodiazepines affected behavior in combination, because the mixture treatment significantly changed several important behavioral traits even at low concentration, while no single compound exposure had such an effect at that dose. Based on our results, we conclude that effects of pharmaceuticals on aquatic environments could be underestimated if risk assessments only rely on the evaluation of single compounds. More studies focused on the combinatory effects of environmentally relevant mixtures of pharmaceuticals are necessary to fill the gaps in this knowledge.

Multi-region assessment of pharmaceutical exposures and predicted effects in USA wadeable urban-gradient streams

Human-use pharmaceuticals in urban streams link aquatic-ecosystem health to human health. Pharmaceutical mixtures have been widely reported in larger streams due to historical emphasis on wastewater-treatment plant (WWTP) sources, with limited investigation of pharmaceutical exposures and potential effects in smaller headwater streams. In 2014-2017, the United States Geological Survey measured 111 pharmaceutical compounds in 308 headwater streams (261 urban-gradient sites sampled 3-5 times, 47 putative low-impact sites sampled once) in 4 regions across the US. Simultaneous exposures to multiple pharmaceutical compounds (pharmaceutical mixtures) were observed in 91% of streams (248 urban-gradient, 32 low-impact), with 88 analytes detected across all sites and cumulative maximum concentrations up to 36,142 ng/L per site. Cumulative detections and concentrations correlated to urban land use and presence/absence of permitted WWTP discharges, but pharmaceutical mixtures also were common in the 75% of sampled streams without WWTP. Cumulative exposure-activity ratios (EAR) indicated widespread transient exposures with high probability of molecular effects to vertebrates. Considering the potential individual and interactive effects of the detected pharmaceuticals and the recognized analytical underestimation of the pharmaceutical-contaminant (unassessed parent compounds, metabolites, degradates) space, these results demonstrate a nation-wide environmental concern and the need for watershed-scale mitigation of in-stream pharmaceutical contamination.

Exposição crônica ao cloridrato de metformina e à glibenclamida causa alterações comportamentais, glicêmicas e de mortalidade em Hemigrammus caudovittatus e Danio rerio

RESUMO Hemigrammus caudovittatus e Danio rerio foram expostos aos hipoglicemiantes orais (HOs) cloridrato de metformina a 40µg/L e 120µg/L e glibenclamida a 0,13µg/L e 0,39µg/L durante 100 dias. Foram avaliados os efeitos tóxicos dos fármacos em relação ao peso, ao comportamento animal, à glicemia e à mortalidade. H. caudovittatus expostos à menor concentração dos fármacos apresentaram aumento significativo (P<0,05) no evento Respiração Aérea. Ainda, foi observado aumento no comportamento Descansar quando os animais foram expostos à glibenclamida a 0,39µg/L. Em D. rerio expostos ao cloridrato de metformina a 120µg/L, foi observado aumento (P<0,05) no comportamento Descansar. A glibenclamida provocou redução (P<0,05) na glicemia de H. caudovittatus. Ambos os fármacos causaram efeito letal na espécie D. rerio, contudo a glibenclamida foi mais tóxica, causando 100% de mortalidade em 30 dias de exposição. Os animais que vieram a óbito apresentaram congestão nos arcos branquiais e hemorragia. Os HOs foram desenvolvidos para apresentarem efeitos fisiológicos em mamíferos, entretanto efeitos tóxicos foram encontrados nas duas espécies de peixe estudadas. Isso levanta a preocupação sobre possíveis efeitos tóxicos de HOs e sobre quais métodos serão utilizados para a sua degradação no ambiente aquático.