Aquatic plants exposed to pharmaceuticals: effects and risks

An enzymatically modified adsorbent derived from an agro-residue mitigates the environmental risks of toxic antibiotic mixtures

This study developed an enzymatically modified adsorbent derived from pine bark (PBEM), an agricultural residue feedstock, for the adsorptive removal of antibiotic contaminants. PBEM was synthesized by optimizing the feedstock selection and modifying it using fungal crude enzymes sustainable recoverable from natural sources. PBEM rapidly removed the antibiotics tetracycline and sulfamethoxazole from a mixed solution much more rapidly (4-99 times faster) and in higher quantities (2-5 times higher) than without enzyme modification. The outperforming removal performance was validated using adsorption kinetics and isotherm parameters over five repeated cycles. Analytical chemistry identified four novel byproducts (BPs) generated in the antibiotic mixture. Quantitative structure-activity relationship analysis revealed that two of these BPs with considerable toxicity potential comparable to the parent compounds, but they were transient and eventually removed using PBEM. As a result, PBEM effectively controlled the toxic effects of the original antibiotics and their BPs much more rapidly than the control adsorbent with no enzyme coating, as illustrated by experimental antimicrobial toxicity testing. These results thus demonstrate the potential of PBEM for both removing various antibiotic residuals via physicochemical adsorption and enzymatic breakdown and completely detoxifying solutions containing antibiotics and their BPs.

Toxic effects of tetracycline on non-target lichen Evernia prunastri

Tetracycline (TC) antibiotics are one of the class of drugs widely used in clinical practice but also constitute a significant environmental concern. However, the adverse effects of TC on non-target organisms have not been well studied. The aim of this study was to examine the influence of exposure to high levels of TC on thalli of lichens to determine the impact on (1) physiological parameters including integrity of cell membranes, photosynthetic efficiency and viability, (2) oxidative stress response such as membrane lipid peroxidation, and (3) enzymatic antioxidant activities as catalase (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), and glutathione reductase (GR). Data demonstrated that exposure to tetracycline did not markedly affect the lichen membrane damage as indicated by no change in conductivity. This antibiotic diminished the potential photosystem II efficiency (FV/FM) indicating enhanced susceptibility as evidenced by lower chlorophyll fluorescence and chlorophyll content. The viability of lichens exposed to high concentrations of tetracycline was significantly reduced. The concentrations of thiobarbituric acid reactive substances were markedly elevated with increasing concentrations of antibiotics. At higher TC concentrations, 500 mg/L SOD activity was significantly elevated. In the case of CAT, APX and GR, TC at higher concentrations significantly decreased these enzymic activities. The findings of this study contribute to the knowledge that TC antibiotics exert adverse ecotoxicological effects on lichens at high concentrations and provided a better understanding of the mechanisms underlying toxicity. Data also indicates that lichens may serve as an effective biomonitoring species for TC antibiotic exposure.

Fluoroquinolone antibiotics in the aquatic environment: environmental distribution, the research status and eco-toxicity

The increasing presence of fluoroquinolone (FQ) antibiotics in aquatic environments is a growing concern due to their widespread use, negatively impacting aquatic organisms. This paper provides an overview of the environmental distribution, sources, fate, and both single and mixed toxicity of FQ antibiotics in aquatic environments. It also examines the accumulation of FQ antibiotics in aquatic organisms and their transfer into the human body through the food chain. The study identifies critical factors such as metabolism characteristics, physiochemical characteristics, light, temperature, dissolved oxygen, and environmental compatibility that influence the presence of FQ antibiotics in aquatic environments. Mixed pollutants of FQ antibiotics pose significant risks to the ecological environment. Additionally, the paper critically discusses advanced treatment technologies designed to remove FQ antibiotics from wastewater, focusing on advanced oxidation processes (AOPs) and electrochemical advanced oxidation processes (EAOPs). The discussion also includes the benefits and limitations of these technologies in degrading FQ antibiotics in wastewater treatment plants. The paper concludes by proposing new approaches for regulating and controlling FQ antibiotics to aid in the development of ecological protection measures.

Utilizing Morphological and Physiological Parameters of Lemna minor for Assessing Tetracyclines' Removal

Antibiotics with significant environmental toxicity, e.g., tetracyclines (TCs), are often used in large quantities worldwide, with 50-80% of the applied dose ending up in the environment. This study aimed to investigate the effects of exposure to tetracycline hydrochloride (TC) and minocycline hydrochloride (MIN) on L. minor. Our research evaluated the phytotoxicity of the TCs by analyzing plant growth and biomass and evaluating assimilation pigment levels and fluorescence. The research was extended with the ability potential of duckweed as a tool for removing TCs from water/wastewater. The results demonstrated that both TCs influenced Ir, Iy, biomass, and photosynthetic efficiency. The uptake of TC and MIN by duckweed was proportional to the concentration in the growth medium. The TC was absorbed more readily, reaching up to 8.09 mg × g-1 of dry weight (DW) at the highest concentration (19.2 mg × L-1), while MIN reached 6.01 mg × g-1 of DW. As indicated, the consequences of the influence of TC on plants were slightly smaller, in comparison to MIN, while the plants could biosorb this drug, even at the lowest tested concentration. This study has shown that using plants for drug biosorption can be an effective standalone or complementary method for water and wastewater treatment.

Seasonal variation in structural and functional distribution of periphyton in a macrolide antibiotics-contaminated river

Periphyton, a microbial assemblage of autotrophic and heterotrophic organisms, is vital to aquatic ecosystems. While exposure to macrolide antibiotics has been confirmed to reduce the biodiversity and damage the critical ecological functions in indoor microcosm bioassays, the distribution of periphyton along a macrolide antibiotic pollution gradient in a river has yet to be determined. Herein, we established the spatiotemporal distribution of five major macrolides, i.e., azithromycin (AZI), roxithromycin (ROX), erythromycin (ERY), clarithromycin (CLA), and anhydro erythromycin (ERY-H2O) in water and periphyton of Zao River (Xi'an, China), after which we evaluated the effects on the structures, photosynthetic activity, and carbon utilization capacity of periphyton in March, June, and September 2023. In contrast with the reference sites, the macrolides were identified in all sewage treatment plants (STPs) impacted sites with concentrations ranging from 0.05 to 2.18 μg/L in water and from not detected - 9.67 μg/g in periphyton. Regarding community structure, the occurrence of macrolides was negatively linked to FirmicutesExiguobacterium undae and Exiguobacterium sibiricum, CyanobacteriaOscillatoriales and Vischeria sp., and ChlorophytaMonostroma grevillei, Selenastrum sp. LU21 and Desmodesmus subspicatus. At the functional level, only the metabolism of phenolic acids was significantly decreased in river reach with high antibiotic levels in June, compared to the other five carbon sources that were not altered. The overall photosynthetic activity of periphytic photosystem II remained unchanged in both reference and STPs impacted groups throughout three seasons. Overall, the macrolides released from STPs were correlated with the altered periphytic structures in the river, whereas a similar trend was not detected for the community functions owing to the functional redundancy. A mesocosm experiments warrants further consideration to validate the field results.

The contemporary nexus of medicines security and bioprospecting: a future perspective for prioritizing the patient

Reacting to the challenges presented by the evolving nexus of environmental change, defossilization, and diversified natural product bioprospecting is vitally important for advancing global healthcare and placing patient benefit as the most important consideration. This overview emphasizes the importance of natural and synthetic medicines security and proposes areas for global research action to enhance the quality, safety, and effectiveness of sustainable natural medicines. Following a discussion of some contemporary factors influencing natural products, a rethinking of the paradigms in natural products research is presented in the interwoven contexts of the Fourth and Fifth Industrial Revolutions and based on the optimization of the valuable assets of Earth. Following COP28, bioprospecting is necessary to seek new classes of bioactive metabolites and enzymes for chemoenzymatic synthesis. Focus is placed on those performance and practice modifications which, in a sustainable manner, establish the patient, and the maintenance of their prophylactic and treatment needs, as the priority. Forty initiatives for natural products in healthcare are offered for the patient and the practitioner promoting global action to address issues of sustainability, environmental change, defossilization, quality control, product consistency, and neglected diseases to assure that quality natural medicinal agents will be accessible for future generations.

Insights in Pharmaceutical Pollution: The Prospective Role of eDNA Metabarcoding

Environmental pollution is a growing threat to natural ecosystems and one of the world's most pressing concerns. The increasing worldwide use of pharmaceuticals has elevated their status as significant emerging contaminants. Pharmaceuticals enter aquatic environments through multiple pathways related to anthropogenic activity. Their high consumption, insufficient waste treatment, and the incapacity of organisms to completely metabolize them contribute to their accumulation in aquatic environments, posing a threat to all life forms. Various analytical methods have been used to quantify pharmaceuticals. Biotechnology advancements based on next-generation sequencing (NGS) techniques, like eDNA metabarcoding, have enabled the development of new methods for assessing and monitoring the ecotoxicological effects of pharmaceuticals. eDNA metabarcoding is a valuable biomonitoring tool for pharmaceutical pollution because it (a) provides an efficient method to assess and predict pollution status, (b) identifies pollution sources, (c) tracks changes in pharmaceutical pollution levels over time, (d) assesses the ecological impact of pharmaceutical pollution, (e) helps prioritize cleanup and mitigation efforts, and (f) offers insights into the diversity and composition of microbial and other bioindicator communities. This review highlights the issue of aquatic pharmaceutical pollution while emphasizing the importance of using modern NGS-based biomonitoring actions to assess its environmental effects more consistently and effectively.

Bismuth-based nanostructured photocatalysts for the remediation of antibiotics and organic dyes

A serious threat to human health and the environment worldwide, in addition to the global energy crisis, is the increasing water pollution caused by micropollutants such as antibiotics and persistent organic dyes. Nanostructured semiconductors in advanced oxidation processes using photocatalysis have recently attracted a lot of interest as a promising green and sustainable wastewater treatment method for a cleaner environment. Due to their narrow bandgaps, distinctive layered structures, plasmonic, piezoelectric and ferroelectric properties, and desirable physicochemical features, bismuth-based nanostructure photocatalysts have emerged as one of the most prominent study topics compared to the commonly used semiconductors (TiO2 and ZnO). In this review, the most recent developments in the use of photocatalysts based on bismuth (e.g., BiFeO3, Bi2MoO6, BiVO4, Bi2WO6, Bi2S3) to remove dyes and antibiotics from wastewater are thoroughly covered. The creation of Z-schemes, Schottky junctions, and heterojunctions, as well as morphological modifications, doping, and other processes are highlighted regarding the fabrication of bismuth-based photocatalysts with improved photocatalytic capabilities. A discussion of general photocatalytic mechanisms is included, along with potential antibiotic and dye degradation pathways in wastewater. Finally, areas that require additional study and attention regarding the usage of photocatalysts based on bismuth for removing pharmaceuticals and textile dyes from wastewater, particularly for real-world applications, are addressed.

Evolution and Emergence of Antibiotic Resistance in Given Ecosystems: Possible Strategies for Addressing the Challenge of Antibiotic Resistance

Antibiotics were once considered the magic bullet for all human infections. However, their success was short-lived, and today, microorganisms have become resistant to almost all known antimicrobials. The most recent decade of the 20th and the beginning of the 21st century have witnessed the emergence and spread of antibiotic resistance (ABR) in different pathogenic microorganisms worldwide. Therefore, this narrative review examined the history of antibiotics and the ecological roles of antibiotics, and their resistance. The evolution of bacterial antibiotic resistance in different environments, including aquatic and terrestrial ecosystems, and modern tools used for the identification were addressed. Finally, the review addressed the ecotoxicological impact of antibiotic-resistant bacteria and public health concerns and concluded with possible strategies for addressing the ABR challenge. The information provided in this review will enhance our understanding of ABR and its implications for human, animal, and environmental health. Understanding the environmental dimension will also strengthen the need to prevent pollution as the factors influencing ABR in this setting are more than just antibiotics but involve others like heavy metals and biocides, usually not considered when studying ABR.

Single and mixture toxicity of selected pharmaceuticals to the aquatic macrophyte Lemna minor

Plants represent uncommon targets to evaluate pharmaceuticals toxicity. In this work, Lemna minor was employed as a plant model to determine the toxicity of selected pharmaceuticals, and to assay if such toxicity could be predicted by QSAR models based on green algae. Among eight compounds, measurable toxicity was determined for ketoprofen (EC₅₀ = 11.8 ± 1.9 mg/L), fluoxetine (EC₅₀ = 27.0 ± 8.7 mg/L) and clindamycin 2-phosphate (EC₅₀ = 57.7 ± 1.7 mg/L). Even though a correlation of r² = 0.87 was observed between experimental toxicity towards algae and L. minor, QSAR estimations based on algae data poorly predicted the toxicity of pharmaceuticals on the plant. More experimental data for L. minor are necessary to determine the applicability of these predictions; nonetheless, these results remark the importance of measuring experimental ecotoxicological parameters for individual taxa. The toxicity of pharmaceutical binary mixtures (ketoprofen, fluoxetine and clindamycin) revealed in some cases deviations from the concentration addition model; nonetheless these deviations were small, thus the interactions are unlikely to be of severe biological significance. Moreover, the EC₅₀ concentrations determined for these pharmaceuticals are significantly higher than those detected in the environment, suggesting that acute effects on L. minor would not take place at ecosystem level.

Pharmaceutical Pollution in Aquatic Environments: A Concise Review of Environmental Impacts and Bioremediation Systems

The presence of emerging contaminants in the environment, such as pharmaceuticals, is a growing global concern. The excessive use of medication globally, together with the recalcitrance of pharmaceuticals in traditional wastewater treatment systems, has caused these compounds to present a severe environmental problem. In recent years, the increase in their availability, access and use of drugs has caused concentrations in water bodies to rise substantially. Considered as emerging contaminants, pharmaceuticals represent a challenge in the field of environmental remediation; therefore, alternative add-on systems for traditional wastewater treatment plants are continuously being developed to mitigate their impact and reduce their effects on the environment and human health. In this review, we describe the current status and impact of pharmaceutical compounds as emerging contaminants, focusing on their presence in water bodies, and analyzing the development of bioremediation systems, especially mycoremediation, for the removal of these pharmaceutical compounds with a special focus on fungal technologies.

Occurrence of antibiotics in waters, removal by microalgae-based systems, and their toxicological effects: A review

Global antibiotics consumption has been on the rise, leading to increased antibiotics release into the environment, which threatens public health by selecting for antibiotic resistant bacteria and resistance genes, and may endanger the entire ecosystem by impairing primary production. Conventional bacteria-based treatment methods are only moderately effective in antibiotics removal, while abiotic approaches such as advanced oxidation and adsorption are costly and energy/chemical intensive, and may cause secondary pollution. Considered as a promising alternative, microalgae-based technology requires no extra chemical addition, and can realize tremendous CO₂ mitigation accompanying growth related pollutants removal. Previous studies on microalgae-based antibiotics removal, however, focused more on the removal performances than on the removal mechanisms, and few studies have concerned the toxicity of antibiotics to microalgae during the treatment process. Yet understanding the removal mechanisms can be of great help for targeted microalgae-based antibiotics removal performances improvement. Moreover, most of the removal and toxicity studies were carried out using environment-irrelevant high concentrations of antibiotics, leading to reduced guidance for real-world situations. Integrating the two research fields can be helpful for both improving antibiotics removal and avoiding toxicological effects to primary producers by the residual pollutants. This study, therefore, aims to build a link connecting the occurrence of antibiotics in the aquatic environment, the removal of antibiotics by microalgae-based processes, and the toxicity of antibiotics to microalgae. Distribution of various categories of antibiotics in different water environments were summarized, together with the antibiotics removal mechanisms and performances in microalgae-based systems, and the toxicological mechanisms and toxicity of antibiotics to microalgae after either short-term or long-term exposure. Current research gaps and future prospects were also analyzed. The review could provide much valuable information to the related fields, and provoke interesting thoughts on integrating microalgae-based antibiotics removal research and toxicity research on the basis of environmentally relevant concentrations.

Emerging contaminant exposure to aquatic systems in the Southern African Development Community

The growing production and use of chemicals and the resultant increase in environmental exposure is of particular concern in developing countries where there is rapid industrialization and population growth but limited information on the occurrence of emerging contaminants. Advances in analytical techniques now allow for the monitoring of emerging contaminants at very low concentrations with the potential to cause harmful ecotoxicological effects. Therefore, we provide the first critical assessment of the current state of knowledge about chemical exposure in waters of the Southern African Developmental Community (SADC). We achieved this through a comprehensive literature review and the creation of a database of chemical monitoring data. Of the 59 articles reviewed, most (n = 36; 61.0%) were from South Africa, and the rest were from Botswana (n = 6; 10.2%), Zimbabwe (n = 6; 10.2%), Malawi (n = 3; 5.1%), Mozambique (n = 3; 5.1%), Zambia (n = 2; 3.4%), Angola (n = 1; 1.7%), Madagascar (n = 1; 1.7%), and Tanzania (n = 1; 1.7%). No publications were found from the remaining seven SADC countries. Emerging contaminants have only been studied in South Africa and Botswana. The antiretroviral drug ritonavir (64.52 µg/L) was detected at the highest average concentration, and ibuprofen (17 times) was detected most frequently. Despite being the primary water source in the region, groundwater was understudied (only 13 studies). High emerging contaminant concentrations in surface waters indicate the presence of secondary sources of pollution such as sewage leakage. We identify research gaps and propose actions to assess and reduce chemical pollution to enable the SADC to address the Sustainable Development Goals, particularly Goal 3.9, to reduce the deaths and illnesses from hazardous chemicals and contamination. Environ Toxicol Chem 2022;41:382-395. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Algae-mediated processes for the treatment of antiretroviral drugs in wastewater: Prospects and challenges

The prevalence of pharmaceuticals (PCs), especially antiretroviral (ARV) drugs in various aquatic ecosystems has been expansively reported, wherein wastewater treatment plants (WWTPs) are identified as the primary point source. Consequently, the occurrence, ecotoxicity and treatment of ARV drugs in WWTPs have drawn much attention in recent years. Numerous studies have shown that the widely employed activated sludge-based WWTPs are incapable of removing ARV drugs efficiently from wastewater. Recently, algae-based wastewater treatment processes have shown promising results in PCs removal from wastewater, either completely or partially, through different processes such as biosorption, bioaccumulation, and intra-/inter-cellular degradation. Algal species have also shown to tolerate high concentrations of ARV drugs than the reported concentrations in the environmental matrices. In this review, emphasis has been given on discussing the current status of the occurrence of ARV drugs in the aquatic environment and WWTPs. Besides, the current trends and future perspectives of PCs removal by algae are critically reviewed and discussed. The potential pathways and mechanisms of ARV drugs removal by algae have also been discussed.

Assessment of pharmaceutical mixture (ibuprofen, ciprofloxacin and flumequine) effects to the crayfish Procambarus clarkii: A multilevel analysis (biochemical, transcriptional and proteomic approaches)

The knowledge about the effects of pharmaceuticals on aquatic organisms has been increasing in the last decade. However, due to the variety of compounds presents in the aquatic medium, exposure scenarios and exposed organisms, there are still many gaps in the knowledge on how mixtures of such bioactive compounds affect exposed non target organisms. The crayfish Procambarus clarkii was used to analyze the toxicity effects of mixtures of ciprofloxacin, flumequine and ibuprofen at low and high concentrations (10 and 100 μg/L) over 21 days of exposure and to assess the recovery capacity of the organism after a depuration phase following exposure during additional 7 days in clean water. The crayfish accumulated the three compounds throughout the entire exposure in the hepatopancreas. The exposure to the mixture altered the abundance of proteins associated with different cells functions such as biotransformation and detoxification processes (i.e. catalase and glutathione transferase), carbohydrate metabolism and immune responses. Additionally changes in expression of genes encoding antioxidant enzymes and in activity of the corresponding enzymes (i.e. superoxide dismutase, glutathione peroxidase and glutathione transferase) were reported. Alterations at different levels of biological organization did not run in parallel under all circumstances and can be related to changes in the redox status of the target tissue. No differences were observed between control and exposed organisms for most of selected endpoints after a week of depuration, indicating that exposure to the drug mixture did not produce permanent damage in the hepatopancreas of P. clarkii.

Oxidation of antibiotics by ferrate(VI) in water: Evaluation of their removal efficiency and toxicity changes

Antibiotics in water and wastewater have been determined extensively. The treatment of antibiotics in water needs evaluation of possible harmful effects on aquatic ecosystems and human health. This paper presents the toxicity evaluation of antibiotics after their treatment with ferrate (VI) (Fe^VIO₄^2-, Fe(VI)) in water. The antibiotics (sulfamethoxazole (SMX), erythromycin (ERY), ofloxacin (OFL), ciprofloxacin (CIP), tetracycline (TET), oxytetracycline (OXY), and trimethoprim (TMP)) were treated at pH 8.0 by applying two concentrations of Fe(VI) to have molar ratios of 5:1 and 10:1 ([Fe(VI)]:[antibiotic]). Under the studied conditions, incomplete removal of antibiotics was observed, suggesting that the treated solutions contained parent antibiotics and their transformation products. The toxicity of antibiotics without Fe(VI) treatment was tested against freshwater green alga Raphidocelis subcapitata and cyanobacterium Synechococcus elongatus, which were determined to be generally sensitive to antibiotics, with EC₅₀ < 1.0 mg/L. The toxicity of Fe(VI) treated solution was tested against R. subcapitata. Results found no toxicity for the treated solutions of OFL, CIP, and OXY. However, SMX, ERY, and TET remained toxic after Fe(VI) treatment (i.e., more than 75% growth inhibition of R. subcapitata). Results demonstrated that R. subcapitata may be applied to test the toxicity of antibiotics after oxidative treatments.

Diclofenac Alters the Cell Cycle Progression of the Green Alga Chlamydomonas reinhardtii

The aim of the study was to verify the hypothesis that a potential cause of the phytotoxicity of diclofenac (DCF, a non-steroidal anti-inflammatory drug) is an effect of cell cycle progression. This research was conducted using synchronous cultures of a model organism, green alga Chlamydomonas reinhardtii. The project examined DCF effects on selected parameters that characterize cell cycle progression, such as cell size, attainment of commitment points, DNA replication, number of nuclei formed during cells division and morphology of cells in consecutive stages of the cell cycle, together with the physiological and biochemical parameters of algae cells at different stages. We demonstrated that individual cell growth remained unaffected, whereas cell division was delayed in the DCF-treated groups grown in continuous light conditions, and the number of daughter cells from a single cell decreased. Thus, the cell cycle progression is a target affected by DCF, which has a similar anti-proliferative effect on mammalian cells.

Sulfamethoxazole-Altered Transcriptomein Green Alga Raphidocelis subcapitata Suggests Inhibition of Translation and DNA Damage Repair

Occurrence of sulfonamide antibiotics has been reported in surface waters with the exposures ranging from < 1 ng L^–1 to approximately 11 μg L^–1, which may exert adverse effects on non-target algal species, inhibiting algal growth and further hindering the delivery of several ecosystem services. Yet the molecular mechanisms of sulfonamide in algae remain undetermined. The aims of the present work are: (1) to test the hypothesis whether sulfamethoxazole (SMX) inhibits the folate biosynthesis in a model green alga Raphidocelis subcapitata; and (2) to explore the effects of SMX at an environmentally relevant concentration on algal health. Here, transcriptomic analysis was applied to investigate the changes at the molecular levels in R. subcapitata treated with SMX at the concentrations of 5 and 300 μg L^–1. After 7-day exposure, the algal density in the 5 μg L^–1 group was not different from that in the controls, whereas a marked reduction of 63% in the high SMX group was identified. Using the adj p < 0.05 and absolute log₂ fold change > 1 as a cutoff, we identified 1 (0 up- and 1 downregulated) and 1,103 (696 up- and 407 downregulated) differentially expressed genes (DEGs) in the 5 and 300 μg L^–1 treatment groups, respectively. This result suggested that SMX at an environmentally relevant exposure may not damage algal health. In the 300 μg L^–1 group, DEGs were primarily enriched in the DNA replication and repair, photosynthesis, and translation pathways. Particularly, the downregulation of base and nucleotide excision repair pathways suggested that SMX may be genotoxic and cause DNA damage in alga. However, the folate biosynthesis pathway was not enriched, suggesting that SMX does not necessarily inhibit the algal growth via its mode of action in bacteria. Taken together, this study revealed the molecular mechanism of action of SMX in algal growth inhibition.

Application of a 2D-QSAR with a sine normalization method for the biodegradation of fluoroquinolones to poison cyanobacteria

Cyanobacteria are photosynthetic autotrophic aquatic prokaryotes. One of the methods for controlling cyanobacterial blooms is to destroy the phycobiliproteins required for photosynthesis. In this study, to improve the biodegradation of the fluoroquinolones through inhibit cyanobacteria, the molecular docking scores of 32 fluoroquinolones (FQs) with four categories of phycobiliproteins from cyanobacteria were calculated after sine normalization to characterize the binding ability between them. A two-dimensional quantitative structure-activity relationship (2D-QSAR) model was constructed based on the comprehensive scores. Danofloxacin (DAN) with the highest comprehensive score was chosen for molecular modification. When docking with four categories of phycobiliproteins from cyanobacteria, the docking values of DAN-11 and DAN-16 were increased up to 35.75%. Moreover, their functional characteristics and environmentally friendly predictive values were improved. When the DAN-11 and DAN-16 molecules docked with the other cyanobacterial phycobiliproteins, indicating that the designed DAN derivatives had general applicability to poison cyanobacteria, the weak interaction forces might increase the binding ability between the DAN derivatives and the receptor phycobiliprotein compared with the target molecule.

Interactions of the Cyanobacterium Chrysosporum ovalisporum with Antibiotics in Water

In this study, we assessed the effects of 11-day exposure of sulfadiazine (SD), sulfamethazine (SM2), norfloxacin (NOR), and enrofloxacin (ENR) on the growth, chlorophyll a (Chl. a) content, phycobiliproteins (PBPs) content, and alkaline phosphatase (ALP) activity of Chrysosporum ovalisporum, examined the removal rate of these antibiotics by C. ovalisporum, and performed acute toxicology test with Daphnia magna to determine the effect of interaction between antibiotics and cyanobacteria on aquatic animals. The results showed that the stress of SD and SM2 increased extracellular ALP activity and weakly inhibited the algal growth and the contents of Chl. a and PBPs compared with that noted in the control. ENR and NOR treatment groups exerted significant inhibition on algal growth as well as Chl. a and PBPs contents and ALP activity, although the cyanobacterium could degrade these two antibiotics more than SD and SM2. The results also revealed that the interaction between antibiotics and cyanobacteria could inhibit D. magna feeding.

Diclofenac and atrazine restrict the growth of a synchronous Chlamydomonas reinhardtii population via various mechanisms

Non-steroidal anti-inflammatory drug diclofenac (DCF) is commonly found in freshwater bodies and can have adverse effects on non-target organisms. Among the studies on DCF toxicity, several ones have reported its harmful effects on plants and algae. To gain a better understanding of the mechanisms of DCF toxicity towards green algae, we used a synchronous Chlamydomonas reinhardtii cc-1690 culture and compared DCF (135 mg/L) effects with effects caused by atrazine (ATR; 77.6 μg/L), an herbicide with a well-known mechanism of toxic action. To achieve our goal, cell number and size, photosynthetic oxygen consumption/evolution, chlorophyll a fluorescence in vivo, H₂O₂ production by the cells, antioxidative enzymes encoding genes expression were analyzed during light phase of the cell cycle. We have found, that DCF and ATR affect C. reinhardtii through different mechanisms. ATR inhibited the photosynthetic electron transport chain and induced oxidative stress in chloroplast. Such chloroplastic energetics disruption indirectly influenced respiration, the intensification of which could partially mitigate low efficiency of photosynthetic energy production. As a result, ATR inhibited the growth of single cell leading to limitation in C. reinhardtii population development. In contrast to ATR-treated algae, in DCF-treated cells the fraction of active PSII reaction centers was diminished without drastic changes in electron transport or oxidative stress symptoms in chloroplast. However, significant increase in transcript level of gene encoding for mitochondria-located catalase indicates respiratory processes as a source of H₂O₂ overproduced in the DCF-treated cells. Because the single cell growth was not strongly affected by DCF, its adverse effect on progeny cell number seemed to be related rather to arresting of cell divisions. Concluding, although the DCF phytotoxic action appeared to be different from the action of the typical herbicide ATR, it can act as algal growth-inhibiting factor in the environment.

Occurrence and risk assessment of fluoroquinolone antibiotics in reclaimed water and receiving groundwater with different replenishment pathways

Artificial recharge to groundwater with reclaimed water is considered a promising method to alleviate groundwater depletion and over-exploitation. However, the occurrence of fluoroquinolone antibiotics (FQs) was ubiquitous in wastewater, surface water, groundwater and even drinking water threating human health and ecology. In this study, the occurrence of six selected FQs in reclaimed water effluent and their removal by tertiary treatment units were investigated. The overall removal efficiencies in average of the tertiary treatment processes in Beijing and Changzhou were ranging from 21.2% to 55.2%. Activated carbon exhibited better performance for FQs removal than ozone and biological treatment such as membrane bioreactor, anaerobic-anoxic-oxic and biofilter. The results of two pilot study showed that the impact of reclaimed water to groundwater quality in terms of FQs concentration by direct injection in GBD was stronger than surface spreading in Changzhou, which might be due to the recharge strategy and the physical and chemical characteristics of sediment and aquifer soil. The hazard quotient (HQ) values of ofloxacin (OFL) in reclaimed water was up to 12.54, indicating the extreme eco-toxicological risk, while enrofloxacin (ENR) exhibited medium risk. After recharge with reclaimed water, the HQ values of OFL and ENR in groundwater ranged from low to medium ecological risk to the environment. Thus, the FQs in reclaimed water need to be paid more attention during their reuse for groundwater recharge, especially by direct injection. It is suggested that FQs should be considered in the priority substances lists in standards and guidelines of reclaimed water reuse for groundwater recharge to ensure the safety of groundwater.

Transcriptomic analysis suggests the inhibition of DNA damage repair in green alga Raphidocelis subcapitata exposed to roxithromycin

Macrolide antibiotics are common contaminants in the aquatic environment. They are toxic to a wide range of primary producers, inhibiting the algal growth and further hindering the delivery of several ecosystem services. Yet the molecular mechanisms of macrolides in algae remain undetermined. The objectives of this study were therefore to: 1. evaluate whether macrolides at the environmentally relevant level inhibit the growth of algae; and 2. test the hypothesis that macrolides bind to ribosome and inhibit protein translocation in algae, as it does in bacteria. In this study, transcriptomic analysis was applied to elucidate the toxicological mechanism in a model green alga Raphidocelis subcapitata treated with 5 and 90 μg L^-1 of a typical macrolide roxithromycin (ROX). While exposure to ROX at 5 μg L^-1 for 7 days did not affect algal growth and the transciptome, ROX at 90 μg L^-1 resulted in 45% growth inhibition and 2306 (983 up- and 1323 down-regulated) DEGs, which were primarily enriched in the metabolism of energy, lipid, vitamins, and DNA replication and repair pathways. Nevertheless, genes involved in pathways in relation to translation and protein translocation and processing were dysregulated. Surprisingly, we found that genes involved in the base excision repair process were mostly repressed, suggesting that ROX may be genotoxic and cause DNA damage in R. subcapitata. Taken together, ROX was unlikely to pose a threat to green algae in the environment and the mode of action of macrolides in bacteria may not be directly extrapolated to green algae.

Occurrence and toxicity of antibiotics in the aquatic environment: A review

In recent years, antibiotics have been used for human and animal disease treatment, growth promotion, and prophylaxis, and their consumption is rising worldwide. Antibiotics are often not fully metabolized by the body and are released into the aquatic environment, where they may have negative effects on the non-target species. This review examines the recent researches on eight representative antibiotics (erythromycin, trimethoprim, sulfamethoxazole, tetracycline, oxytetracycline, ofloxacin, ciprofloxacin, and amoxicillin). A detailed overview of their concentrations in surface waters, groundwater, and effluents is provided, supported by recent global human consumption and veterinary use data. Furthermore, we review the ecotoxicity of these antibiotics towards different groups of organisms, and assessment of the environmental risks to aquatic organisms. This review discusses and compares the suitability of currently used ecotoxicological bioassays, and identifies the knowledge gaps and future challenges. The risk data indicate that selected antibiotics may pose a threat to aquatic environments. Cyanobacteria were the most sensitive organisms when using standard ecotoxicological bioassays. Further studies on their chronic effects to aquatic organisms and the toxicity of antibiotic mixtures are necessary to fully understand the hazards these antibiotics present.

Morpho-physiological responses by Isochrysis galbana Parke to different concentrations of oxytetracycline

The pollution of aquatic bodies by pharmaceutical compounds is an emerging environmental problem, with little explored consequences. Oxytetracycline (OTC) is an antibiotic used for treatment of infections caused by a variety of microorganisms and it is widely employed in medicine, livestock husbandry and aquaculture. This pharmaceutical compound may cause deleterious effects on non-target aquatic organisms as microalgae. The objective of this study was to evaluate the effects of OTC on growth, pigment content and morpho-physiology of the microalga Isochrysis galbana Parke. The results highlighted that OTC exposure inhibited the growth of I. galbana in cultures treated with OTC 5.0 and 10.0 mg/L after 3 days and in cultures treated with OTC 5.0, 7.5 and 10.0 mg/L after 5 days. Effects of OTC on cells ultrastructure and physiology consisted in large cytoplasmic lipid inclusions and in a decrease of photosynthetic pigments amount.

Spatial variation in the detection rates of frequently studied pharmaceuticals in Asian, European and North American rivers

Pharmaceutical consumption has expanded rapidly during the last century and their persistent presence in the environment has become a major concern. Unfortunately, our understanding of the distribution of pharmaceuticals in surface water and their effects on aquatic biota and public health is limited. Here, we explore patterns in the detection rate of the most frequently studied pharmaceuticals in 64 rivers from 22 countries using bi-clustering algorithms and subsequently analyze the results in the context of regional differences in pharmaceutical consumption habits, social and environmental factors, and removal-efficiency of wastewater treatment plants (WWTP). We find that 20% of the pharmaceuticals included in this analysis are pervasively present in all the surface waterbodies. Several pharmaceuticals also display low overall positive detection rates; however, they exhibit significant spatial variability and their detection rates are consistently lower in Western European and North America (WEOG) rivers in comparison to Asian rivers. Our analysis suggests the important role of pharmaceutical consumption and population in governing these patterns, however the role of WWTP efficiency appeared to be limited. We were constrained in our ability to assess the role of hydrology, which most likely also plays an important role in regulating pharmaceuticals in rivers. Most importantly though, we demonstrate the ability of our algorithm to provide probabilistic estimates of the detection rate of pharmaceuticals that were not studied in a river, an exercise that could be useful in prioritizing pharmaceuticals for future study.

Aeromonas spp. Isolated from Pacific Abalone (Haliotis discus hannai) Marketed in Korea: Antimicrobial and Heavy-Metal Resistance Properties

Antimicrobial and heavy-metal resistance of 29 Aeromonas spp. (Aeromonas hydrophila n = 9, Aeromonas enteropelogenes n = 14, Aeromonas veronii n = 3, Aeromonas salmonicida n = 2, and Aeromonas sobria n = 1) isolated from Pacific abalone marketed in Korea were analyzed. All isolates were found to be resistant against ampicillin. High level of resistant to cephalothin (86%), rifampicin (73%), imipenem (42%), and oxytetracycline (35%) were also detected. Thirteen (45%) of the isolates showed multiple antimicrobial resistance (MAR) index ≥ 0.2. The PCR assays implied the presence of qnrS, qnrB, qnrA, tetB, tetA, aac (3')- IIa, aac(6')-Ib, aphAI-IAB, bla_CTX, bla_TEM, and intI1 genes among 76%, 28%, 14%, 17%, 3%, 3%, 41%, 10%, 41%, 28%, and 66% of the isolates, respectively. Class 1 integron gene cassette profiles aadA1(3%) and aadA2 (3%) were also identified. Lead (Pb) resistance was the highest (69%) among 5 heavy metals tested, whereas 38%, 27%, and 20% of the isolates were resistant to Cadmium (Cd), Chromium (Cr), and Copper (Cu), respectively. Heavy-metal resistance genes, CopA, CzcA, and merA were positive in 83%, 75%, and 41% of the isolates, respectively. In conclusion, observed genotypic and phenotypic resistance profiles of Aeromonas spp. against antimicrobials and heavy metals reveal the ability of serving as a source of antimicrobials and heavy-metal-resistant traits.

A critical review on antibiotics and hormones in swine wastewater: Water pollution problems and control approaches

Swine wastewater (SW) is an important source of antibiotics and hormones (A&H) in the environment due to their large-scale application in swine industry. A&H in SW can be released into the water environment through the direct discharge of SW, effluent from SW treatment plants, and runoff and leaching from farmland polluted by swine wastes. The presence of A&H in the water environment has become an increasing global concern considering their adverse effects to the aquatic organism and human. This review critically discusses: (i) the occurrence of A&H in global water environment and their potential risks to water organisms and human; (ii) the management and technical approaches for reducing the emission of A&H in SW to the water environment. The development of antibiotic alternatives and the enhanced implementation of vaccination and biosecurity are promising management approaches to cut down the consumption of antibiotics during swine production. Through the comparison of different biological treatment technologies for removing A&H in SW, membrane-based bioprocesses have relatively higher and more stable removal efficiencies. Whereas, the combined system of bioprocesses and AOPs is expected to be a promising technology for elimination and mineralization of A&H in swine wastewater. Further study on this system is therefore necessary.

Comparison of oxidative stress induced by clarithromycin in two freshwater microalgae Raphidocelis subcapitata and Chlorella vulgaris

Clarithromycin (CLA), a macrolide antibiotic, has been frequently detected in the global surface waters. Concerns have been raised over the potential impacts of CLA on the non-target aquatic species, particularly algae acting as the primary producers in the ecosystem. This study therefore evaluated the toxicological effects of CLA at a range of concentration levels (0, 5, 20, 40, 80 μg L^-1) on two green algae, Raphidocelis subcapitata (R. subcapitata) and Chlorella vulgaris (C. vulgaris). The algal growth, photosynthetic pigment contents, lipid peroxidation biomarker malondialdehyde (MDA), responses of antioxidants including superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione peroxidase (GP), and glutathione S-transferase (GST) were measured. After 7 d exposure, the growth of R. subcapitata was inhibited with the CLA exposure levels higher than 20 μg L^-1, whereas the inhibition in C. vulgaris was detected at the concentration level of 80 μg L^-1. The MDA contents in both species were elevated. To cope with the increased levels of ROS, the activities of enzymatic antioxidants (SOD, CAT, GP, and GST) and the content of non-enzymatic antioxidant (GSH) in R. subcapitata were all enhanced. However, in C. vulgaris, enhancement was detected only in the activities of antioxidant enzymes (SOD, CAT, and GP). In addition, chlorophyll a, b, and carotenoid contents were all significantly increased in R. subcapitata but decreased in C. vulgaris. The results suggested that R. subcapitata is more sensitive to CLA exposure than C. vulgaris. This study provides insights into the CLA - oxidative stress process in two algae.

Assessment of the Risks of the Major Use Antibiotics in China's Surface Waters Using a Probabilistic Approach

The occurrence of antibiotics in China's surface waters is an emerging concern. Although the ecological risk assessment for a small number of antibiotics is available in some regions, no attempt has been made to assess their risks at a national scale. The present work therefore proposed a probabilistic approach to characterize the ecological risks of 26 major use antibiotics, including sulfonamides, tetracyclines, beta-lactams, fluoroquinolones, and macrolides, in China's surface waters. Initially we performed exposure and hazard assessment for these substances by synthesizing and interpreting the available occurrence and ecotoxicity data. For 22 antibiotics with sufficient ecotoxicity data, we assessed their risks by constructing joint probability curves (JPCs), from which their expected ecological risk (EER) estimates were less than 1%; for all the 26 antibiotics, in conjunction with the exposure distribution curves (EDCs), an assessment factor (AF) approach was applied and the potential risks were only detected for amoxicillin, ciprofloxacin, and penicillin with risk quotients (RQs) of 1.04, 1.54, and 5.83, respectively. These results indicated that the ecological risks of most major use antibiotics posed to nontarget organisms in China's aquatic environment seem to be low. Nevertheless, there are large uncertainties in the risk characterization processes, likely because of the significant data gaps in the understanding of exposure and hazards of these antibiotics. Integr Environ Assess Manag 2019;00:1-10. © 2019 SETAC.

Emerging investigator series: towards a framework for establishing the impacts of pharmaceuticals in wastewater irrigation systems on agro-ecosystems and human health

Use of reclaimed wastewater for agricultural irrigation is seen as an attractive option to meet agricultural water demands of a growing number of countries suffering from water scarcity. However, reclaimed wastewater contains pollutants which are introduced to the agro-environment during the irrigation process. While water reuse guidelines do consider selected classes of pollutants, they do not account for the presence of pollutants of emerging concern such as pharmaceuticals and the potential risks these may pose. Here we use source-pathway-receptor analysis (S-P-R) to develop a holistic framework for evaluating the impacts of pharmaceuticals, present in wastewater used for agricultural irrigation, on human and ecosystem health and evaluate the data availability for the framework components. The developed framework comprised of 34 processes and compartments but a good level of knowledge was available for only five of these suggesting that currently it is not possible to fully establish the impacts of pharmaceuticals in wastewater irrigation systems. To address this, work is urgently needed to understand the fate and transport of pharmaceuticals in arable soil systems and the effects of chronic low-level exposure to these substances on microbes, invertebrates, plants, wildlife and humans. In addition, research pertaining to the fate, uptake and effects of pharmaceutical mixtures and metabolites is lacking as well as data on bio-accessibility of pharmaceuticals after ingestion. Scientific advancements in the five areas prioritised in terms of future research are needed before we are able to fully quantify the agricultural and human health risks associated with reclaimed wastewater use.

Degradation kinetics of cold plasma-treated antibiotics and their antimicrobial activity

Antibiotics, such as ofloxacin (OFX) and ciprofloxacin (CFX), are often detected in considerable concentrations in both wastewater effluents and surface water. This poses a risk to non-target organisms and to human health. The aim of this work was to study atmospheric cold plasma (ACP) degradation of antibiotics in water and meat effluent and to explore any residual antimicrobial activity of samples submitted to the plasma process. The results revealed that ACP successfully degraded the studied antibiotics and that the reaction mechanism is principally related to attack by hydroxyl radicals and ozone. According to the disk diffusion assay, the activity of both antibiotics was considerably reduced by the plasma treatment. However, a microdilution method demonstrated that CFX exhibited higher antimicrobial activity after ACP treatment than the corresponding control revealing a potentially new platform for future research to improve the efficiency of conventional antibiotic treatments. Importantly, short-term exposures to sub-lethal concentrations of the antibiotic equally reduced bacterial susceptibility to both ACP treated and untreated CFX. As a remediation process, ACP removal of antibiotics in complex wastewater effluents is possible. However, it is recommended that plasma encompass degradant structure activity relationships to ensure that biological activity is eliminated against non-target organisms and that life cycle safety of antibiotic compounds is achieved.

Sensitivities of seven algal species to triclosan, fluoxetine and their mixtures

Increasing release of pharmaceuticals and personal care products (PPCPs) into aquatic ecosystems is a growing environmental concern. Triclosan and fluoxetine are two widely used PPCPs and frequently detected in aquatic ecosystems. In this study, the sensitivities of 7 algal species from 4 genera to triclosan, fluoxetine and their mixture were evaluated. The results showed that the inhibitory effect on algal growth (EC₅₀-96h) of triclosan varied with 50 times differences among the 7 algal species. Chlorella ellipsoidea was the least susceptible species and Dunaliella parva was the most sensitive species to triclosan. The inhibitory effect of fluoxetine was less variable than triclosan. Slightly higher toxicity of fluoxetine than triclosan was shown in the 7 tested algal species. No consistent pattern of the effects from mixture of triclosan and fluoxetine was observed among the 7 algal species and among the 4 genera. Additive effects of the mixture occured in 4 species and antagonistic effects in the other 3 species but no synergistic effect was detected. The algal species might show some sign of phylogenetic response to triclosan, as evidenced by the wide range of differences in their sensitivity at the genus level. This study provides important data which could be beneficial for biomonitoring programs on the ecological risk (algal species diversity) of these two chemicals.

Phytotoxic activity of diclofenac: Evaluation using a model green alga Chlamydomonas reinhardtii with atrazine as a reference substance

Human activities have caused increasing inputs of pharmaceuticals to the environment and diclofenac (DF) is one of the most commonly detected in freshwater systems. The aim of this study was to determine the impact of DF on a freshwater green alga as a non-target organism. For DF toxicity evaluation, its effects on a model organism Chlamydomonas reinhardtii were compared with effects caused by the herbicide atrazine (AT). EC₅₀ values were about 135 mg/L for DF and 78 mg/L for AT, respectively. Both toxicants enhanced H₂O₂ production by the cells (144% and 178% of control for AT and DF, respectively) and stimulated catalase activity (≈200% of control). Activity of ascorbate peroxidase was elevated in AT-cells but not in DF-treated cells. DF did not influence dark respiration of the cells, whereas AT inhibited this process by about 50% compared to the control. Both toxicants caused photosynthesis inhibition. Analysis of parameters of chlorophyll a fluorescence in vivo showed diminishment of a performance index (PI) in both DF- and AT-treated cells (≈50% of control), but the reasons for the changes detected were different. AT diminished the efficiency of electron transport between PS II and PS I without significant inhibition of PS II or PS I reaction centers (RCs). In contrast to AT, DF seemed to influence directly PS II RCs. The fraction of active PS II RCs was lowered in DF-treated cells, but energy flux per active RC increased. Our study indicates that DF phytotoxicity results mainly from photosynthesis inhibition due to "silencing" of a fraction of PS II RCs.

Select antibiotics in leachate from closed and active landfills exceed thresholds for antibiotic resistance development

Though antibiotic resistance (ABR) represents a major global health threat, contributions of landfill leachate to the life cycle of antibiotics and ABR development are poorly understood in rapidly urbanizing regions of developing countries. We selected one of the largest active landfills in Asia and two landfills that have been closed for 20 years to examine antibiotic occurrences in leachates and associated hazards during wet and dry season sampling events. We focused on some of the most commonly used human antibiotics in Hong Kong, one of the most populous Asian cities and the fourth most densely populated cities in the world. Seven antibiotics (cephalexin [CLX], chloramphenicol [CAP], ciprofloxacin [CIP], erythromycin [ERY], roxithromycin [ROX], trimethoprim [TMP], sulfamethoxazole [SMX]) were quantitated using HPLC-MS/MS generally following previously reported methods. Whereas CLX, CAP, ROX and SMX in leachates did not exceed ABR predicted no effect concentrations (PNECs), exceedances were observed for CIP, ERY and TMP in some study locations and on some dates. In fact, an ABR PNEC for CIP was exceeded in leachates during both sampling periods from all study locations, including leachates that are directly discharged to coastal systems. These findings highlight the importance of developing an advanced understanding of pharmaceutical access, usage and disposal practices, effectiveness of intervention strategies (e.g., leachate treatment technologies, drug take-back schemes), and contributions of landfill leachates to the life cycle of antibiotics and ABR development, particularly in rapidly urbanizing coastal regions with less advanced waste management systems than Hong Kong.

Intraspecific variability of ciprofloxacin accumulation, tolerance, and metabolism in Chinese flowering cabbage (Brassica parachinensis)

To investigate the mechanism of genotype differences in ciprofloxacin (CIP) accumulation, this study was designed to compare the tolerance and metabolic responses to CIP exposure between low (Cutai) and high (Sijiu) CIP-accumulation cultivars of Brassica parachinensis. Decreases in biomass and chlorophyll content were significantly greater (p < 0.05) and toxicities were more severe within cell ultrastructures of Cutai compared to Sijiu. A sequential growth test also revealed that Sijiu was more tolerant to CIP stress compared to Cutai. Meanwhile, significantly higher (p < 0.05) root parameters and higher areas of the stele and xylem may be responsible for the increased uptake and transport of CIP in Sijiu. Ultra performance liquid chromatography-electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) analysis revealed that CIP was metabolized to three major metabolites by the hydroxylation and breakdown of the piperazinyl substituent in the CIP molecule. The enhanced metabolic transformation of CIP in Sijiu indicated a more efficient capacity to detoxify, which in turn favored an increased accumulation of CIP in this cultivar. Thus, the present study demonstrated that the stronger tolerance and metabolism of Sijiu to CIP were responsible for its high CIP accumulation, suggesting an evolutionary mechanism for adaptation to environmental stress.

Effects of temperature, genetic variation and species competition on the sensitivity of algae populations to the antibiotic enrofloxacin

Primary producers are amongst the most sensitive organisms to antibiotic pollution in aquatic ecosystems. To date, there is little information on how different environmental conditions may affect their sensitivity to antibiotics. In this study we assessed how temperature, genetic variation and species competition may affect the sensitivity of the cyanobacterium Microcystis aeruginosa and the green-algae Scenedesmus obliquus to the antibiotic enrofloxacin. First, we performed single-species tests to assess the toxicity of enrofloxacin under different temperature conditions (20°C and 30°C) and to assess the sensitivity of different species strains using a standard temperature (20°C). Next, we investigated how enrofloxacin contamination may affect the competition between M. aeruginosa and S. obliquus. A competition experiment was performed following a full factorial design with different competition treatments, defined as density ratios (i.e. initial bio-volume of 25/75%, 10/90% and 1/99% of S. obliquus/M. aeruginosa, respectively), one 100% S. obliquus treatment and one 100% M. aeruginosa treatment, and four different enrofloxacin concentrations (i.e. control, 0.01, 0.05 and 0.10mg/L). Growth inhibition based on cell number, bio-volume, chlorophyll-a concentration as well as photosynthetic activity were used as evaluation endpoints in the single-species tests, while growth inhibition based on measured chlorophyll-a was primarily used in the competition experiment. M. aeruginosa photosynthetic activity was found to be the most sensitive endpoint to enrofloxacin (EC50-72h =0.02mg/L), followed by growth inhibition based on cell number. S. obliquus was found to be slightly more sensitive at 20°C than at 30°C (EC50-72h cell number growth inhibition of 38 and 41mg/L, respectively), whereas an opposite trend was observed for M. aeruginosa (0.047 and 0.037mg/L, respectively). Differences in EC50-72h values between algal strains of the same species were within a factor of two. The competition experiment showed that M. aeruginosa growth can be significantly reduced in the presence of S. obliquus at a density ratio of 75/25% M. aeruginosa/S. obliquus, showing a higher susceptibility to enrofloxacin than in the single-species test. The results of this study confirm the high sensitivity of cyanobacteria to antibiotics and show that temperature and inter-strain genetic variation may have a limited influence on their response to them. The results of the competition experiment suggest that the structure of primary producer communities can be affected, at least temporarily, at antibiotic concentrations close to those that have been measured in the environment.

Recovery of Lemna minor after exposure to sulfadimethoxine irradiated and non-irradiated in a solar simulator

Sulfonamides are the second most widely used group of veterinary antibiotics which are often detected in the environment. They are eliminated from freshwaters mainly through photochemical degradation. The toxicity of sulfadimethoxine (SDM) was evaluated with the use of Lemna minor before and after 1- and 4-h irradiation in a SunTest CPS+ solar simulator. Eight endpoints consisting of: number and total area of fronds, fresh weight, chlorophylls a and b, carotenoids, activity of catalase and guaiacol peroxidase, and protein content were determined. The total frond area and chlorophyll b content were the most sensitive endpoints with EC50 of 478 and 554 μg  L^-1, respectively. The activity of guaiacol peroxidase and catalase increased at SDM concentrations higher than 125 and 500 μg  L^-1, respectively. The SDM photodegradation rate for first order kinetics and the half-life were 0.259 h^-1 and 2.67  h, respectively. The results show that the toxicity of irradiated solutions was caused by SDM only, and the photoproducts appeared to be either non-toxic or much less toxic to L. minor than the parent compound. To study the recovery potential of L. minor, after 7 days exposure in SDM solutions, the plants were transferred to fresh medium and incubated for the next 7 days. L. minor has the ability to regenerate, but a 7-day recovery phase is not sufficient for it to return to an optimal physiological state.

Integrating human and environmental health in antibiotic risk assessment: A critical analysis of protection goals, species sensitivity and antimicrobial resistance

Antibiotics are vital in the treatment of bacterial infectious diseases but when released into the environment they may impact non-target organisms that perform vital ecosystem services and enhance antimicrobial resistance development with significant consequences for human health. We evaluate whether the current environmental risk assessment regulatory guidance is protective of antibiotic impacts on the environment, protective of antimicrobial resistance, and propose science-based protection goals for antibiotic manufacturing discharges. A review and meta-analysis was conducted of aquatic ecotoxicity data for antibiotics and for minimum selective concentration data derived from clinically relevant bacteria. Relative species sensitivity was investigated applying general linear models, and predicted no effect concentrations were generated for toxicity to aquatic organisms and compared with predicted no effect concentrations for resistance development. Prokaryotes were most sensitive to antibiotics but the range of sensitivities spanned up to several orders of magnitude. We show reliance on one species of (cyano)bacteria and the 'activated sludge respiration inhibition test' is not sufficient to set protection levels for the environment. Individually, neither traditional aquatic predicted no effect concentrations nor predicted no effect concentrations suggested to safeguard for antimicrobial resistance, protect against environmental or human health effects (via antimicrobial resistance development). Including data from clinically relevant bacteria and also more species of environmentally relevant bacteria in the regulatory framework would help in defining safe discharge concentrations for antibiotics for patient use and manufacturing that would protect environmental and human health. It would also support ending unnecessary testing on metazoan species.

The role of graphene oxide and graphene oxide-based nanomaterials in the removal of pharmaceuticals from aqueous media: a review

In this review paper, the ill effects of pharmaceuticals (PhAs) on the environment and their adsorption on graphene oxide (GO) and graphene oxide-based (GO-based) nanomaterials have been summarised and discussed. The adsorption of prominent PhAs discussed herein includes beta-blockers (atenolol and propranolol), antibiotics (tetracycline, ciprofloxacin and sulfamethoxazole), pharmaceutically active compounds (carbamazepine) and analgesics such as diclofenac. The adsorption of PhAs strictly depends upon the experimental conditions such as pH, adsorbent and adsorbate concentrations, temperature, ionic strength, etc. To understand the adsorption mechanism and feasibility of the adsorption process, the adsorption isotherms, thermodynamics and kinetic studies were also considered. Except for some cases, GO and its derivatives show excellent adsorption capacities for PhAs, which is crucial for their applications in the environmental pollution cleanup.

Effects of erythromycin, trimethoprim and clindamycin on attached microbial communities from an effluent dominated prairie stream

In this study, differing metrics were utilized to measure effects of erythromycin (ER), trimethoprim (TR) and clindamycin (CL) on the structure and function of attached Wascana Creek, SK microbial communities. All three test antibiotics, especially ER, affected community structure and function of biofilms grown in rotating annular reactors. Biofilm thickness, bacterial biomass, and lectin binding biovolume (exopolymeric substances) were consistently less in ER treated biofilms when compared to the control. As well negative effects on protozoan numbers, and carbon utilization were detected. Finally, PCA analyses of DGGE results indicated that bacterial community diversity in ER exposed biofilms was always different from the control. ER exhibited toxic effects even at lower concentrations. Observations on TR and CL exposed biofilms indicated that bacterial biomass, lectin binding biovolume and carbon utilization were negatively affected as well. In terms of bacterial community diversity, however, CL exposed biofilms tended to group with the control while TR grouped with nutrient additions suggesting both nutritive and toxic effects. This study results represent an important step in understanding antibiotic effects, especially ER, on aquatic microbial communities. And because ER is so ubiquitous in receiving water bodies worldwide, the Wascana study results suggest the possibility of ecosystem disturbance elsewhere.

CAPSULE ABSTRACT

Erythromycin (ER) is ubiquitous in waterbodies receiving sewage effluent. Structure and function of microbial communities from an effluent dominated stream were negatively affected by ER, at realistic concentrations.

Aquatic environmental risk assessment for human use of the old antibiotic sulfamethoxazole in Europe

Sulfamethoxazole (SMX) is an old sulfonamide antibiotic that was launched first in combination with trimethoprim in 1969 by F.Hoffmann-La Roche. Although sales figures for SMX have been declining over the past 20 yr, the compound is still widely used; moreover, many measured environmental concentrations (MECs) are available from Europe, the United States, Asia, Australia, and Africa. To assess aquatic risks of SMX in Europe, the exposure of European surface waters was predicted based on actual sales figures from IMS Health, incorporating environmental fate data on one side, and based on collated MECs representing more than 5500 single measurements in Europe on the other. Environmental effects were assessed using chronic and subchronic ecotoxicity data for 16 groups of aquatic organisms, from periphyton communities to cyanobacteria, algae, higher plants, various invertebrates, and vertebrates. Predicted no-effect concentrations (PNECs) were derived using both deterministic and probabilistic methodology. The predicted environmental concentration (PEC)/PNEC and MEC/PNEC comparisons overall showed no appreciable risk, except in a low incidence (<0.55%) of cases in which exceptionally high MECs led to MEC/PNEC risk characterization ratios greater than 1. The PNECs derived in the present study can be used to extend aquatic environmental risk assessment for SMX to other continents. No risk appears for indirect human exposure to SMX via the environment.

Evaluation of the potential for trophic transfer of roxithromycin along an experimental food chain

Pharmaceuticals have been recognized as a new class of environmental pollutants in recent years. But data about their potential for transfer and biomagnification in aquatic food chains are still lacking. In this study, bioaccumulation of the macrolide antibiotic roxithromycin (ROX) was determined in an experimental aquatic food chain involving the green algae Scenedesmus obliquus, the water flea Daphnia magna and the crucian carp Carassius auratus. After 48 h of exposure, S. obliquus accumulated ROX from media, with bioconcentration factors (BCFs) of 74.6, 46.3, and 24.5 l kg(-1) at nominal exposure concentrations of 4, 20, and 100 μg l(-1), respectively. After 48 h of feeding ROX-contaminated algae, D. magna was able to accumulate ROX in all three concentration treatments, but biomagnification did not occur at this trophic level, as biomagnification factors (BMFs) varied from 0.21 to 0.29 in different concentration treatments were well below one. In tissues (muscle, gill, liver, and bile) of C. auratus fed with contaminated daphnia for 8 days, no biomagnification was observed. However, this species did accumulate a certain degree of ROX through food chain transfer, and the tissue burden was greatest in the liver > muscle > gill and lowest in the bile. This work suggests that the trophic transfer should be a matter of concern for ecological risk assessments of pharmaceutical substances in aquatic food webs.

Physiological effects of tetracycline antibiotic pollutants on non-target aquatic Microcystis aeruginosa

This study aimed to evaluate the aquatic toxicity of three typical tetracycline antibiotics, including tetracycline, oxytetracycline, and chlortetracycline, on the cyanobacterium Microcystis aeruginosa. The cell density, chlorophyll a content, protein content, and enzymatic antioxidant activities were determined. The results showed that the cell growth was significantly inhibited by the three compounds at a low concentration. The chlorophyll a and protein content decreased significantly after exposure to 0.05 mg L(-1) of each compound for 9 d. When exposed to 0.2-1 mg L(-1) of tetracycline, the superoxide dismutase (SOD) activity increased, but peroxidase (POD) and catalase (CAT) activities decreased. In contrast, when exposed to oxytetracycline and chlortetracycline at different concentrations ranging from 0.2 to 1 mg L(-1) and from 0.01 to 0.05 mg L(-1), the SOD activity decreased, but the POD and CAT activities increased. These findings indicate that tetracycline antibiotics influence cell growth and protein synthesis, and they also induce oxidative stress in M. aeruginosa at environmentally similar concentrations. Thus, this study may provide further insights into the toxic effects of tetracycline antibiotics and the controlled use of antibiotics.

Accounting for dissociation and photolysis: a review of the algal toxicity of triclosan

Triclosan, an antimicrobial agent commonly used in down-the-drain consumer products, is toxic to freshwater microalgae. However, the rapid photolysis and pH-dependent dissociation of this compound may give rise to uncertainty in growth inhibition tests with freshwater microalgae, if these are not well characterized. Methods are presented to minimize these uncertainties by stabilizing pH with an organic buffering agent (Bis-Tris) and by the application of ultraviolet (UV) covers to remove UV wavelengths. Toxicity tests with these methods were in compliance with the validity criteria of the Organisation for Economic Co-operation and Development test 201, and no negative effects were seen in controls relative to the unmodified method. The methods were used for toxicity tests with triclosan at pH levels of 7.0, 8.0, and 8.5, yielding effective concentration, 10% values of 0.5 µg/L, 0.6 µg/L, and 12.1 µg/L, respectively. The observed change in toxicity with pH was proportional to the change in bioconcentration factor (BCF) as calculated using the cell model (a dynamic flux model based on the Fick-Nernst-Planck equations, in this case parameterized for an algal cell). Effect concentrations produced with the methods presented in the present study offer robust data on which to base risk assessment, and it is suggested that similar approaches be used to minimize uncertainty when other compounds that dissociate and photolyse are tested.

Biochemical and standard toxic effects of acetaminophen on the macrophyte species Lemna minor and Lemna gibba

Acetaminophen is globally one of the most prescribed drugs due to its antipyretic and analgesic properties. However, it is highly toxic when the dosage surpasses the detoxification capability of an exposed organism, with involvement of an already described oxidative stress pathway. To address the issue of the ecotoxicity of acetaminophen, we performed acute exposures of two aquatic plant species, Lemna gibba and Lemna minor, to this compound. The selected biomarkers were number of fronds, biomass, chlorophyll content, lipid peroxidation (TBARS assay), and proline content. Our results showed marked differences between the two species. Acetaminophen caused a significant decrease in the number of fronds (EC50 = 446.6 mg/L), and the establishment of a dose-dependent peroxidative damage in L. minor, but not in L. gibba. No effects were reported in both species for the indicative parameters chlorophyll content and total biomass. However, the proline content in L. gibba was substantially reduced. The overall conclusions point to the occurrence of an oxidative stress scenario more prominent for L. minor. However, the mechanisms that allowed L. gibba to cope with acetaminophen exposure were distinct from those reported for L. minor, with the likely involvement of proline as antioxidant.

Fish on Prozac (and Zoloft): ten years later

A decade has now passed since our research group initially reported several adverse effects of fluoxetine to aquatic organisms commonly employed for developing environmental quality criteria, evaluating whole effluent toxicity, and monitoring ambient toxicity of surface waters and sediments. Our subsequent observation of fluoxetine, sertraline and their active metabolites (norfluoxetine and desmethylsertraline, respectively) accumulating in muscle, liver and brain tissues of three different fish species from an effluent-dominated stream was termed "Fish on Prozac." Here I briefly review some scientific lessons learned from our study of antidepressants and the environment, including opportunities for research, management, environmental education and public outreach. Intrinsic chemical properties of antidepressants and other pharmaceuticals have afforded research in areas ranging from analytical chemistry and comparative pharmacology, to influences of ionization, chirality and adverse outcome pathways on hazard and risk assessment, and further promises to support sustainable molecular design of less hazardous chemicals. Using probabilistic hazard assessment and fish plasma modeling approaches, selective serotonin reuptake inhibitors and tricyclic antidepressants are predicted to result in therapeutic hazard to fish (internal fish plasma level equaling mammalian therapeutic dose) when exposed to water (inhalational) at or below 1μg/L, a common trigger value for environmental assessments. Though many questions remain unanswered, studies of antidepressants in urbanizing aquatic systems have provided, and will continue to develop, an advanced understanding of environmental hazards and risks from pharmaceuticals and other contaminants.

Occurrences and fate of selected human antibiotics in influents and effluents of sewage treatment plant and effluent-receiving river Yamuna in Delhi (India)

Antibiotics consumption has increased worldwide, and their residues are frequently reported in aquatic environments. It is believed that antibiotics reach aquatic water bodies through sewage. Medicine consumed for healthcare practices are often released into sewage, and after sewage treatment plant, it reaches the receiving water bodies of lakes or rivers. In the present study, we determined the fate of some commonly used antibiotics in a sewage treatment plant (STP) located in Delhi and the environmental concentration of these antibiotics in the Yamuna River, which receives the sewage and industrial effluent of Delhi. There are many reports on antibiotics occurrences in STP and river water worldwide, but monitoring data from the Indian subcontinent is sparse. Samples were taken from a STP and from six sampling sites on the Yamuna River. Several antibiotics were tested for using offline solid-phase extraction followed by high-performance liquid chromatography equipped with photodiode array analysis. Recoveries varied from 25.5-108.8 %. Ampicillin had the maximum concentration in wastewater influents (104.2 ± 98.11 μg l(-1)) and effluents (12.68 ± 8.38 μg l(-1)). The fluoroquinolones and cephalosporins had the lower concentrations. Treatment efficiencies varied between 55 and 99 %. Significant amounts of antibiotics were discharged in effluents and were detected in the receiving water body. The concentration of antibiotics in the Yamuna River varied from not detected to 13.75 μg l(-1) (ampicillin) for the compounds investigated.