Risk assessment of chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin in aquatic environment: are the current environmental concentrations safe?

A Novel Method for the Assessment of Feeding Rate as a Phenotypic Endpoint for the Impact of Pollutants in Daphnids

Traditional approaches for monitoring aquatic pollution primarily rely on chemical analysis and the detection of pollutants in the aqueous environments. However, these methods lack realism and mechanistic insight and, thus, are increasingly supported by effect-based methods, which offer sensitive endpoints. In this context, daphnids, a freshwater species used extensively in molecular ecotoxicology, offer fast and noninvasive approaches to assess the impact of pollutants. Among the phenotypic endpoints used, feeding rate is a highly sensitive approach because it provides evidence of physiological alterations even in sublethal concentrations. However, there has been no standardized method for measuring feeding rate in daphnids, and several approaches follow different protocols. There is a diversity among tests employing large volumes, extensive incubation times, and high animal densities, which in turn utilize measurements of algae via fluorescence, radiolabeling, or counting ingested cells. These tests are challenging and laborious and sometimes require cumbersome instrumentation. In the present study, we optimized the conditions of a miniaturized fast, sensitive, and high-throughput assay to assess the feeding rate based on the ingestion of fluorescent microparticles. The protocol was optimized in neonates in relation to the concentration of microplastic and the number of animals to increase reproducibility. Daphnids, following exposures to nonlethal concentrations, were incubated with microplastics; and, as filter feeders, they ingest microparticles. The new approach revealed differences in the physiology of daphnids in concentrations below the toxicity limits for a range of pollutants of different modes of action, thus proving feeding to be a more sensitive and noninvasive endpoint in pollution assessment. Environ Toxicol Chem 2024;43:2211-2221. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Review on antibiotic pollution dynamics: insights to occurrence, environmental behaviour, ecotoxicity, and management strategies

Antibiotic contamination poses a significant global concern due to its far-reaching impact on public health and the environment. This comprehensive review delves into the prevalence of various antibiotic classes in environmental pollution and their interactions with natural ecosystems. Fluoroquinolones, macrolides, tetracyclines, and sulphonamides have emerged as prevalent contaminants in environmental matrices worldwide. The concentrations of these antibiotics vary across diverse environments, influenced by production practices, consumer behaviours, and socio-economic factors. Low- and low-middle-income countries face unique challenges in managing antibiotic contamination, with dominant mechanisms like hydrolysis, sorption, and biodegradation leading to the formation of toxic byproducts. Ecotoxicity reports reveal the detrimental effects of these byproducts on aquatic and terrestrial ecosystems, further emphasizing the gravity of the issue. Notably, monitoring the antibiotic parent compound alone may be inadequate for framing effective control and management strategies for antibiotic pollution. This review underscores the imperative of a comprehensive, multi-sectoral approach to address environmental antibiotic contamination and combat antimicrobial resistance. It also advocates for the development and implementation of tailored national action plans that consider specific environmental conditions and factors. Thus, an approach is crucial for safeguarding both public health and the delicate balance of our natural ecosystems.

Ecotoxicity of five veterinary antibiotics on indicator organisms and water and soil communities

This study explores the environmental effects of five common veterinary antibiotics widely detected in the environment, (chlortetracycline,CTC; oxytetracycline,OTC; florfenicol,FF; neomycin, NMC; and sulfadiazine, SDZ) on four bioindicators: Daphnia magna, Vibrio fischeri, Eisenia fetida, and Allium cepa, representing aquatic and soil environments. Additionally, microbial communities characterized through 16 S rRNA gene sequencing from a river and natural soil were exposed to the antibiotics to assess changes in population growth and metabolic profiles using Biolog EcoPlates™. Tetracyclines are harmful to Vibrio fisheri (LC50 ranges of 15-25 µg/mL), and the other three antibiotics seem to only affect D. magna, especially, SDZ. None of the antibiotics produced mortality in E. fetida at concentrations below 1000 mg/kg. NMC and CTC had the highest phytotoxicities in A. cepa (LC50 = 97-174 µg/mL, respectively). Antibiotics significantly reduced bacterial metabolism at 0.1-10 µg/mL. From the highest to the lowest toxicity on aquatic communities: OTC > FF > SDZ ≈ CTC > NMC and on edaphic communities: CTC ≈ OTC > FF > SDZ > NMC. In river communities, OTC and FF caused substantial decreases in bacterial metabolism at low concentrations (0.1 µg/mL), impacting carbohydrates, amino acids (OTC), and polymers (FF). At 10 µg/mL and above, OTC, CTC, and FF significantly decreased metabolizing all tested metabolites. In soil communities, a more pronounced decrease in metabolizing ability, detectable at 0.1 µg/mL, particularly affected amines/amides and carboxylic and ketonic acids (p < 0.05). These new ecotoxicity findings underscore that the concentrations of these antibiotics in the environment can significantly impact both aquatic and terrestrial ecosystems.

Degradation of norfloxacin by red mud-based prussian blue activating H2O2: A strategy for treating waste with waste

The massive accumulation of red mud (RM) and the abuse of antibiotics pose a threat to environment safety and human health. In this study, we synthesized RM-based Prussian blue (RM-PB) by acid solution-coprecipitation method to activate H2O2 to degrade norfloxacin, which reached about 90% degradation efficiency at pH 5 within 60 min and maintained excellent catalytic performance over a wide pH range (3-11). Due to better dispersion and unique pore properties, RM-PB exposed more active sites, thus the RM-PB/H2O2 system produced more reactive oxygen species. As a result, the removal rate of norfloxacin by RM-PB/H2O2 system was 8.58 times and 2.62 times of that by RM/H2O2 system and PB/H2O2 system, respectively. The reactive oxygen species (ROS) produced in the degradation process included ·OH, ·O2- and 1O2, with 1O2 playing a dominant role. The formation and transformation of these ROS was accompanied by the Fe(III)/Fe(II) cycle, which was conducive for the sustained production of ROS. The RM-PB/H2O2 system maintained a higher degradation efficiency after five cycles, and the material exhibited strong stability, with a low iron leaching concentration. Further research showed the degradation process was less affected by Cl-, SO42-, NO3-, and humic acids, but was inhibited by HCO3- and HPO42-. In addition, we also proposed the possible degradation pathway of norfloxacin. This work is expected to improve the resource utilization rate of RM and achieve treating waste with waste.

Ethylparaben Toxicity on Cladocerans Daphnia Similis and Ceriodaphnia Silvestrii and Species Sensitivity Analysis

Parabens, a group of preservatives with a wide industrial range, threaten human and aquatic biota health due to their toxicity and endocrine disruption potential. As conventional wastewater treatment may not be enough to keep natural environments safe, toxicity studies are useful tools for supporting ecological risk assessments. Here, we focused on assessing ethylparaben's, one of the most common kinds of paraben, toxicity in the cladocerans Daphnia similis and Ceriodaphnia silvestrii. The EC50 sensitivity for D. similis and C. silvestrii was 24 (21-28) mg L- 1 and 25 (19-33) mg L- 1, respectively. Inhibition of reproduction and late development of females were observed in C. silvestrii exposed to 8 mg L- 1. Furthermore, species sensitivity distribution was used to assess ecological risk, and ethylparaben demonstrated low potential risk for aquatic biota.

A systematic review of the evaluation of endocrine-disrupting chemicals in the Japanese medaka (Oryzias latipes) fish

Japanese medaka (Oryzias latipes) is an acceptable small laboratory fish model for the evaluation and assessment of endocrine-disrupting chemicals (EDCs) found in the environment. In this research, we used this fish as a potential tool for the identification of EDCs that have a significant impact on human health. We conducted an electronic search in PubMed (http://www.ncbi.nlm.nih.gov/pubmed) and Google Scholar (https://scholar.google.com/) using the search terms, Japanese medaka, Oryzias latipes, and endocrine disruptions, and sorted 205 articles consisting of 128 chemicals that showed potential effects on estrogen-androgen-thyroid-steroidogenesis (EATS) pathways of Japanese medaka. From these chemicals, 14 compounds, namely, 17β-estradiol (E2), ethinylestradiol (EE2), tamoxifen (TAM), 11-ketotestosterone (11-KT), 17β-trenbolone (TRB), flutamide (FLU), vinclozolin (VIN), triiodothyronine (T3), perfluorooctanoic acid (PFOA), tetrabromobisphenol A (TBBPA), terephthalic acid (TPA), trifloxystrobin (TRF), ketoconazole (KTC), and prochloraz (PCZ), were selected as references and used for the identification of apical endpoints within the EATS modalities. Among these endpoints, during classification, priorities are given to sex reversal (masculinization of females and feminization of males), gonad histology (testis-ova or ovotestis), secondary sex characteristics (anal fin papillae of males), plasma and liver vitellogenin (VTG) contents in males, swim bladder inflation during larval development, hepatic vitellogenin (vtg) and choriogenin (chg) genes in the liver of males, and several genes, including estrogen-androgen-thyroid receptors in the hypothalamus-pituitary-gonad/thyroid axis (HPG/T). After reviewing 205 articles, we identified 108 (52.68%), 46 (22.43%), 19 (9.26%), 22 (17.18%), and 26 (12.68%) papers that represented studies on estrogen endocrine disruptors (EEDs), androgen endocrine disruptors (AEDs), thyroid endocrine disruptors (TEDs), and/or steroidogenesis modulators (MOS), respectively. Most importantly, among 128 EDCs, 32 (25%), 22 (17.18%), 15 (11.8%), and 14 (10.93%) chemicals were classified as EEDs, AEDs, TEDs, and MOS, respectively. We also identified 43 (33.59%) chemicals as high-priority candidates for tier 2 tests, and 13 chemicals (10.15%) show enough potential to be considered EDCs without any further tier-based studies. Although our literature search was unable to identify the EATS targets of 45 chemicals (35%) studied in 60 (29.26%) of the 205 articles, our approach has sufficient potential to further move the laboratory-based research data on Japanese medaka for applications in regulatory risk assessments in humans.

Selection of priority emerging contaminants in surface waters of India, Pakistan, Bangladesh, and Sri Lanka

The challenge of emerging contaminants (ECs) in global surface water bodies and particularly in low- and middle-income countries such as India, Pakistan, Bangladesh, and Sri Lanka, is evident from the literature. The complexity arises from the high costs involved in EC analysis and the extensive list of ECs, which complicates the selection of essential compounds for scientific and regulatory investigations. Consequently, monitoring programs often include ECs that may have minimal significance within a region and do not pose known or suspected ecological or human health risks. This study aims to address this issue by employing a multi-risk assessment approach to identify priority ECs in the surface waters of the aforementioned countries. Through an analysis of occurrence levels and frequency data gathered from published literature, an optimized risk quotient (RQ) was derived. The findings reveal a priority list of 38 compounds that exhibit potential environmental risks and merit consideration in future water quality monitoring programs. Furthermore, the majority of antibiotics in India (12 out of 17) and Pakistan (7 out of 17) exhibit a risk quotient for antimicrobial resistance selection (RQAMR) greater than 1, highlighting the need for devising effective strategies to mitigate the escalation of antibiotic resistance in the environment.

Mechanistic insights into hormesis induced by erythromycin in the marine alga Thalassiosira weissflogii

Erythromycin (ERY) is a typical macrolide antibiotic with large production and extensive use on a global scale. Detection of ERY in both freshwaters and coaster seawaters, as well as relatively high ecotoxicity of ERY have been documented. Notably, hormesis has been reported on several freshwater algae under ERY stress, where growth was promoted at relatively lower exposures but inhibited at higher treatment levels. On the contrary, there is limited information of ERY toxicity in marine algae, hampering the risk assessment on ERY in the coaster waters. The presence of hormesis may challenge the current concept of dose-response adopted in chemical risk assessment. Whether and how exposure to ERY can induce dose-dependent toxicity in marine algae remain virtually unknown, especially at environmentally relevant concentrations. The present study used a model marine diatom Thalassiosira weissflogii (T. weissflogii) to reveal its toxicological responses to ERY at different biological levels and decipher the underlying mechanisms. Assessment of multiple apical endpoints shows an evident growth promotion following ERY exposure at an environmentally relevant concentration (1 µg/L), associated with increased contents reactive oxygen species (ROS) and chlorophyll-a (Chl-a), activated signaling pathways related to ribosome biosynthesis and translation, and production of total soluble protein. By contrast, growth inhibition in the 750 and 2500 µg/L treatments was attributed to reduced viability, increased ROS formation, reduced content of total soluble protein, inhibited photosynthesis, and perturbed signaling pathways involved in xenobiotic metabolism, ribosome, metabolism of amino acid, and nitrogen metabolism. Measurements of multiple apical endpoints coupled with de novo transcriptomics analysis applied in the present study, a systems biology approach, can generate detailed mechanistic information of chemical toxicity including dose-response and species sensitivity difference used in environmental risk assessment.

Direct and gut microbiota-mediated toxicities of environmental antibiotics to fish and aquatic invertebrates

The accumulation of antibiotics in the environment has ecological impacts that have received less attention than the human health risks of antibiotics, although the effects could be far-reaching. This review discusses the effects of antibiotics on the health of fish and zooplankton, manifesting in direct or dysbiosis-mediated physiological impairment. Acute effects of antibiotics in these organism groups are usually induced at high concentrations (LC₅₀ at ∼100-1000 mg/L) that are not commonly present in aquatic environments. However, when exposed to sub-lethal, environmentally relevant levels of antibiotics (ng/L-μg/L) disruption of physiological homeostasis, development, and fecundity can occur. Antibiotics at similar or lower concentrations can induce dysbiosis of gut microbiota which can affect the health of fish and invertebrates. We show that the data about molecular-level effects of antibiotics at low exposure concentrations are limited, hindering environmental risk assessment and species sensitivity analysis. Fish and crustaceans (Daphnia sp.) were the two groups of aquatic organisms used most often for antibiotic toxicity testing, including microbiota analysis. While low levels of antibiotics impact the composition and function of gut microbiota in aquatic organisms, the correlation and causality of these changes to host physiology are not straightforward. In some cases, negative or lack of correlation have occurred, and, unexpectedly, gut microbial diversity has been unaffected or increased upon exposure to environmental levels of antibiotics. Efforts to incorporate functional analyses of gut microbiota are beginning to provide valuable mechanistic information, but more data is needed for ecological risk assessment of antibiotics.

Freshwater crustacean exposed to active pharmaceutical ingredients: ecotoxicological effects and mechanisms

Concerns over the ecotoxicological effects of active pharmaceutical ingredients (APIs) on aquatic invertebrates have been raised in the last decade. While numerous studies have reported the toxicity of APIs in invertebrates, no attempt has been made to synthesize and interpret this dataset in terms of different exposure scenarios (acute, chronic, multigenerational), multiple crustacean species, and the toxic mechanisms. In this study, a thorough literature review was performed to summarize the ecotoxicological data of APIs tested on a range of invertebrates. Therapeutic classes including antidepressants, anti-infectives, antineoplastic agents, hormonal contraceptives, immunosuppressants, and neuro-active drugs exhibited higher toxicity to crustaceans than other API groups. The species sensitivity towards APIs exposure is compared in D. magna and other crustacean species. In the case of acute and chronic bioassays, ecotoxicological studies mainly focus on the apical endpoints including growth and reproduction, whereas sex ratio and molting frequency are commonly used for evaluating the substances with endocrine-disrupting properties. The multigenerational and "Omics" studies, primarily transcriptomics and metabolomics, were confined to a few API groups including beta-blocking agents, blood lipid-lowing agents, neuroactive agents, anticancer drugs, and synthetic hormones. We emphasize that in-depth studies on the multigenerational effects and the toxic mechanisms of APIs on the endocrine systems of freshwater crustacean are warranted.

Responses of zebrafish (Danio rerio) cells to antibiotic erythromycin stress at the subcellular levels

Erythromycin (ERY) is one of the most used antibiotics frequently detected in different aquatic environments and may bring burdens to aquatic ecosystems. However, the impacts of antibiotics on aquatic systems other than the antibiotic resistance genes remain largely unknown. In the present study, the responses to ERY exposure at the subcellular-organelle levels were for the first time investigated and imaged over 24 h. Exposure to ERY hampered the zebrafish (Danio rerio) cell growth and decreased the cell viability in a time-dependent mode. Meanwhile, exposure to a low concentration of ERY (73.4 μg L^-1) induced reactive oxygen species (ROS) overproduction and lysosomal damage following lysosomal alkalization and swelling. In turn, the lysosomal stress was the major driver of altering the ROS level, superoxide dismutase (SOD) activity, and glutathione (GSH) content. Subsequently, mitochondria displayed dysfunction such as increased mitochondrial ROS, impaired mitophagy, and induced mitochondria-driven apoptosis, as well as impaired mitochondrial electron transport chain and loss of membrane potential. These results collectively demonstrated the subcellular sensitive machinery responses to ERY stress at environmentally relevant and slightly higher sub-lethal concentrations. ERY may induce switching from autophagy to apoptosis with corresponding changes in lysosomal activity, antioxidant activity, and mitochondrial activity. The findings provided important information on the physiological and subcellular responses of fish cells to ERY.

Influence of co-exposure to sulfamethazine on the toxicity and bioaccumulation kinetics of chlorpyrifos in zebrafish (Danio rerio)

Pesticides and antibiotics are frequently present in aquatic environment which may pose potential risks to aquatic organisms. However, the interaction of pesticides and antibiotics in co-exposure model remains unclear. Here, the effects of the co-exposure of sulfamethazine (SMZ) on the toxicity and bioaccumulation of the organophosphorus insecticide chlorpyrifos (CPF) in zebrafish (Danio rerio) were explored. The 96-h LC₅₀ of chlorpyrifos to zebrafish was 1.36 mg/L and sulfamethazine at 1 mg/L slightly increased the acute toxicity with the 96-h LC₅₀ of 1.20 mg/L which was not significant. The 30-day co-exposure of chlorpyrifos with sulfamethazine at 1 mg/L aggravated the oxidative stress, decreased CarE and AChE activity, and increased CYP450 activity significantly. Furthermore, the co-exposure reduced the accumulation of chlorpyrifos and sulfamethazine while prolonged their depuration duration. The results demonstrated the exposure risk of chlorpyrifos to zebrafish may be enhanced in the presence of sulfamethazine.

Effects of oxytetracycline on aerobic granular sludge process: Granulation, biological nutrient removal and microbial community structure

Formation of aerobic granular sludge (AGS), process performance and microbial community structure were investigated in lab-scale sequencing batch reactors (SBR) operated without and with oxytetracycline (OTC). Granulation of activated sludge and appearance of AGS was observed in parallel SBRs operated without and with OTC. However, formation of well-settling aerobic granules was relatively faster in the SBR fed with 100 μg/L OTC and observed within 2 weeks of start-up. Ammonium, total nitrogen, and phosphorus removals were quickly established in the AGS cultivated without OTC. In contrast, nitrogen and phosphorus removals were lower in the OTC fed SBR. But, a gradual improvement in nitrogen and phosphorus removals was observed. After 45 days, nitrogen and phosphorous removals were stabilized at 99% and 70%, respectively, due to establishment of OTC-tolerant community. qPCR revealed the impact of OTC on ammonium oxidizing bacteria, polyphosphate accumulating organisms and their enrichment during exposure to OTC. Ammonium and phosphorus were majorly removed via nitritation-denitritation and enhanced biological phosphorus removal (EBPR) pathways, respectively, in the presence of OTC. Brevundimonas (35%), Thaurea (14%) sp. Ca. Competibacter (5.6%), and Ca. Accumulibacter (4.2%) were enriched in OTC-fed AGS. Of the two OTC-tolerant strains isolated, Micrococcus luteus exhibited growth and efficient OTC biotransformation at different OTC concentrations. Moreover, M. luteus was predominantly growing in the form of aggregates. Key traits such as tolerance, biotransformation and high autoaggregation ability allowed a niche for this strain in the granules. This work has important implications in understanding the effect of antibiotics on AGS and designing AGS based treatment for antibiotic-laden wastewaters.

Tellurium-based chemical sensors

The various tellurium-based chemical sensors are described. This article focuses on four types of Tellurium sensors such as CdTe quantum dots-based sensor, Te thin films-based sensor, Te nanostructures or nanoparticles-based sensor, and TeO2-based sensor.

Antibiotic Chlortetracycline Causes Transgenerational Immunosuppression via NF-κB

The extensive and increasing global use of antibiotics results in the ubiquitous presence of antibiotics in the environment, which has made them "pseudo persistent organic contaminants." Despite numerous studies showing wide adverse effects of antibiotics on organisms, the chronic environmental risk of their exposure is unknown, and the molecular and cellular mechanisms of antibiotic toxicity remain unclear. Here, we systematically quantified transgenerational immune disturbances after chronic parental exposure to environmental levels of a common antibiotic, chlortetracycline (CTC), using zebrafish as a model. CTC strongly reduced the antibacterial activities of fish offspring by transgenerational immunosuppression. Both innate and adaptive immunities of the offspring were suppressed, showing significant perturbation of macrophages and neutrophils, expression of immune-related genes, and other immune functions. Moreover, these CTC-induced immune effects were either prevented or alleviated by the supplementation with PDTC, an antagonist of nuclear factor-κB (NF-κB), uncovering a seminal role of NF-κB in CTC immunotoxicity. Our results provide the evidence in fish that CTC at environmentally relevant concentrations can be transmitted over multiple generations and weaken the immune defense of offspring, raising concerns on the population hazards and ecological risk of antibiotics in the natural environment.

Fluoxetine Removal from Aqueous Solutions Using a Lignocellulosic Substrate Colonized by the White-Rot Fungus Pleurotus ostreatus

One of the main challenges in both the design of new wastewater treatment plants and the expansion and improvement of existing ones is the removal of emerging pollutants. Therefore, the search for economic and sustainable treatments is needed to enhance the removal of pharmaceuticals. The potential of a lignocellulosic substrate colonized by Pleurotus ostreatus, a waste from mushroom production, to remove fluoxetine from aqueous solutions was studied. Batch assays were performed to remove 600 µg∙L⁻¹ fluoxetine from aqueous solutions using the colonized mushroom substrate (CMS) and crude enzyme extracts. The removal efficiencies achieved were, respectively, ≥83.1% and 19.6% in 10 min. Batch assays with sterilized CMS and 1-aminobenzotriazole (to inhibit cytochrome P450 enzymes) showed that the higher removal efficiencies achieved in the CMS assays may be attributed to the synergistic contribution of biosorption onto the CMS and lignin modifying enzymes activity, namely laccase activity. A column assay was performed with the CMS, fed with 750 µg∙L⁻¹ fluoxetine aqueous solution. The removal efficiency was 100% during 30 min, decreasing to a final value of 70% after 8 h of operation. The results suggested that CMS can be a promising eco-friendly alternative to remove fluoxetine from aqueous solutions.

The use of non-target high-resolution mass spectrometry screening to detect the presence of antibiotic residues in urban streams of Greensboro North Carolina

Antibiotic pollution in aquatic systems is a concern for human and environmental health. The concern is largely due to the global occurrence of antibiotic-resistant bacteria. From 2017 to 2018 in the NC Piedmont, 15 ion masses associated with antibiotics were detected in rural streams and groundwater. Four of these masses were confirmed to be antibiotics through target analysis (sulfamethoxazole, sulfamerazine, erythromycin, danofloxacin). Concentrations of antibiotics were as high as 1.8 μg/L. As a follow-up, antibiotic residues in urban streams sites in Greensboro, NC, USA, were investigated. Urban streams are heavily influenced by the dense populations surrounding them. In the fall, winter, and spring seasons, surface water was collected from eight sites along two urban streams. Sampling was conducted at streams sites above and below municipal hospitals and wastewater treatment facilities in the study area. At the conclusion of the survey, nine ion masses associated with antibiotics used in both human and veterinary medicine were detected from surface water collected. Three of the four antibiotics targeted in rural stream samples were detected and confirmed in urban stream samples (sulfamerazine, danofloxacin, and erythromycin). Detection frequencies of the three antibiotics ranged from 0 to 46%. Concentrations of each target antibiotic was as followed: SMX (0 to <10 ng/L), SMR (0 to <11 ng/L), DAN (0 to <20 ng/L), and ETM (0 to <15 ng/L). Each target antibiotic concentration was below our methods quantification limits. Our risk assessment analysis showed that the target antibiotics posed no risk to fish, daphnia, and green algae within this region of NC (RQ < 0.1). Compared to rural streams in this region of NC, antibiotic pollution is less prevalent in urban streams. The differences between urban and rural streams may be driven by the varying land use and suggest more research should be dedicated to monitoring these contaminants in rural areas of the United States.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00688-9.

Aquatic concentration and risk assessment of pharmaceutically active compounds in the environment

Pharmaceutically active compounds are increasingly detected in raw and treated wastewater, surface water, and drinking water worldwide. These compounds can cause adverse effects to the ecosystem even at low concentrations and, to assess these impacts, toxicity tests are essential. However, the toxicity data are scarce for many PhACs, and when available, they are dispersed in the literature. The values of pharmaceuticals concentration in the environment and toxicity data are essential for measuring their environmental and human health risks. Thus this review verified the concentrations of pharmaceuticals in the aquatic environment and the toxicity related to them. The risk assessment was also carried out. Diclofenac, naproxen, erythromycin, roxithromycin, and 17β-estradiol presented a high environment risk and 17α-ethinylestradiol presented a high human health risk. This shows the potential of these pharmaceuticals to cause adverse effects to the ecosystem and humans and establishes the necessity of their removal through advanced technologies.

Environmental impacts of COVID-19 treatment: Toxicological evaluation of azithromycin and hydroxychloroquine in adult zebrafish

One of the most impact issues in recent years refers to the COVID-19 pandemic, the consequences of which thousands of deaths recorded worldwide, are still inferior understood. Its impacts on the environment and aquatic biota constitute a fertile field of investigation. Thus, to predict the impact of the indiscriminate use of azithromycin (AZT) and hydroxychloroquine (HCQ) in this pandemic context, we aim to assess their toxicological risks when isolated or in combination, using zebrafish (Danio rerio) as a model system. In summary, we observed that 72 h of exposure to AZT and HCQ (alone or in binary combination, both at 2.5 μg/L) induced the reduction of total protein levels, accompanied by increased levels of thiobarbituric acid reactive substances, hydrogen peroxide, reactive oxygen species and nitrite, suggesting a REDOX imbalance and possible oxidative stress. Molecular docking analysis further supported this data by demonstrating a strong affinity of AZT and HCQ with their potential antioxidant targets (catalase and superoxide dismutase). In the protein-protein interaction network analysis, AZT showed a putative interaction with different cytochrome P450 molecules, while HCQ demonstrated interaction with caspase-3. The functional enrichment analysis also demonstrated diverse biological processes and molecular mechanisms related to the maintenance of REDOX homeostasis. Moreover, we also demonstrated an increase in the AChE activity followed by a reduction in the neuromasts of the head when zebrafish were exposed to the mixture AZT + HCQ. These data suggest a neurotoxic effect of the drugs. Altogether, our study demonstrated that short exposure to AZT, HCQ or their mixture induced physiological alterations in adult zebrafish. These effects can compromise the health of these animals, suggesting that the increase of AZT and HCQ due to COVID-19 pandemic can negatively impact freshwater ecosystems.

Toxicokinetic Models for Bioconcentration of Organic Contaminants in Two Life Stages of White Sturgeon (Acipenser transmontanus)

The white sturgeon (Acipenser transmontanus) is an endangered ancient fish species that is known to be particularly sensitive to certain environmental contaminants, partly because of the uptake and subsequent toxicity of lipophilic pollutants prone to bioconcentration as a result of their high lipid content. To better understand the bioconcentration of organic contaminants in this species, toxicokinetic (TK) models were developed for the embryo-larval and subadult life stages. The embryo-larval model was designed as a one-compartment model and validated using whole-body measurements of benzo[a]pyrene (B[a]P) metabolites from a waterborne exposure to B[a]P. A physiologically based TK (PBTK) model was used for the subadult model. The predictive power of the subadult model was validated with an experimental data set of four chemicals. Results showed that the TK models could accurately predict the bioconcentration of organic contaminants for both life stages of white sturgeon within 1 order of magnitude of measured values. These models provide a tool to better understand the impact of environmental contaminants on the health and the survival of endangered white sturgeon populations.

Ecological Risk Assessment of Amoxicillin, Enrofloxacin, and Neomycin: Are Their Current Levels in the Freshwater Environment Safe?

Veterinary pharmaceuticals may cause unexpected adverse effects on non-target aquatic species. While these pharmaceuticals were previously identified as priority compounds in ambient water, their ecological risks are relatively unknown. In this study, a series of chronic toxicity tests were conducted for these pharmaceuticals using algae, two cladocerans, and a fish. After a 21-d exposure to amoxicillin, enrofloxacin, and neomycin, no observed effect concentration (NOEC) for the reproduction of Daphnia magna was detected at 27.2, 3.3, and 0.15 mg/L, respectively. For the survival of juvenile Oryzias latipes following the 40-d exposure, NOEC was found at 21.8, 3.2, and 0.87 mg/L, respectively. Based on the results of the chronic toxicity tests and those reported in the literature, predicted no-effect concentrations (PNECs) were determined at 0.078, 4.9, and 3.0 µg/L for amoxicillin, enrofloxacin, and neomycin, respectively. Their hazard quotients (HQs) were less than 1 at their average levels of occurrence in ambient freshwater. However, HQs based on the maximum detected levels of amoxicillin and enrofloxacin were determined at 21.2 and 6.1, respectively, suggesting potential ecological risks. As the potential ecological risks of these veterinary pharmaceuticals at heavily contaminated sites cannot be ignored, hotspot delineation and its management are required.

Fenton-like degradation of sulfathiazole using copper-modified MgFe-CO3 layered double hydroxide

The catalytic activity of layered double hydroxides, with and without insertion of copper, was evaluated in a heterogeneous Fenton process for degradation of the antibiotic sulfathiazole (STZ). The characterizations with different techniques revealed lamellar structures formed by stacking of layers containing magnesium, iron, and copper cations. The insertion of copper in the lamellar structure increased the specific area of the material and the degradation kinetics, achieving complete STZ removal after 90 min. X-ray photoelectron spectroscopy analysis showed the presence of Cu(II) and Cu(I) surface sites, which contributed to the generation of hydroxyl and hydroperoxyl/superoxide radicals. It also indicated an increase of Cu(I) content after use. For both materials, but specially for LDH without copper, addition of tert-butyl alcohol and p-benzoquinone hindered STZ degradation, indicating the importance of hydroxyl and hydroperoxyl/superoxide radicals in the degradation process, respectively. These results demonstrated the potential of copper-modified MgFe-CO₃ as a catalyst for the degradation of emerging contaminants, offering the benefits of easy preparation and high efficiency in the Fenton process.

Recent trends in advanced oxidation process-based degradation of erythromycin: Pollution status, eco-toxicity and degradation mechanism in aquatic ecosystems

Wide spread documentation of antibiotic pollution is becoming a threat to aquatic environment. Erythromycin (ERY), a macrolide belonging antibiotic is at the top of this list with its concentrations ranging between ng/L to a few μg/L in various global waterbodies giving rise to ERY-resistance genes (ERY-RGs) and ERY- resistance bacteria (ERY-RBs) posing serious threat to the aquatic organisms. ERY seems resistant to various conventional water treatments, remained intact and even increased in terms of mass loads after treatment. Enhanced oxidation potential, wide pH range, elevated selectivity, adaptability and greater efficiency makes advance oxidation processes (AOPs) top priority for degrading pollutants with aromatic rings and unsaturated bonds like ERY. In this manuscript, recent developments in AOPs for ERY degradation are reported along with the factors that affect the degradation mechanism. ERY, marked as a risk prioritized macrolide antibiotic by 2015 released European Union watch list, most probably due to its protein inhibition capability considered third most widely used antibiotic. The current review provides a complete ERY overview including the environmental entry sources, concentration in global waters, ERY status in STPs, as well as factors affecting their functionality. Along with that this study presents complete outlook regarding ERY-RGs and provides an in depth detail regarding ERY's potential threats to aquatic biota. This study helps in figuring out the best possible strategy to tackle antibiotic pollution keeping ERY as a model antibiotic because of extreme toxicity records.

Sulfonamide drugs: structure, antibacterial property, toxicity, and biophysical interactions

Sulfonamide (or sulphonamide) functional group chemistry (SN) forms the basis of several groups of drug. In vivo sulfonamides exhibit a range of pharmacological activities, such as anti-carbonic anhydrase and anti-t dihydropteroate synthetase allowing them to play a role in treating a diverse range of disease states such as diuresis, hypoglycemia, thyroiditis, inflammation, and glaucoma. Sulfamethazine (SMZ) is a commonly used sulphonamide drug in veterinary medicine that acts as an antibacterial compound to treat livestock diseases such as gastrointestinal and respiratory tract infections. Sulfadiazine (SDZ) is another frequently employed sulphonamide drug that is used in combination with the anti-malarial drug pyrimethamine to treat toxoplasmosis in warm-blooded animals. This study explores the research findings and the work behaviours of SN (SMZ and SDZ) drugs. The areas covered include SN drug structure, SN drug antibacterial activity, SN drug toxicity, and SN environmental toxicity.

Antibiotics Modulate Intestinal Regeneration

Simple Summary

The impact of the microbial community on host’s biological functions has uncovered the potential outcomes of antibiotics on host physiology, introducing the caveats of the antibiotic usage. Within animals, the digestive function is closely related to the microorganisms that inhabit this organ. The proper maintenance of the digestive system requires constant regeneration. These processes vary from self-renewal of some cells or tissues in some species to the complete regeneration of the organ in others. Whether antibiotics influence digestive organ regeneration remains unknown. We employ the sea cucumber, Holothuria glaberrima, for its capacity to regenerate the whole intestine after ejection from its internal cavity. We explored the antibiotics’ effects on several intestinal regeneration processes. In parallel, we studied the effect of antibiotics on the animals’ survival, toxicity, and gut bacteria growth. Our results show that tested antibiotics perturbed key cellular processes that occur during intestinal regeneration. Moreover, this happens at doses that inhibited bacteria growth but did not alter holothurian’s metabolic activity. We propose that antibiotics can perturb the cellular events of intestinal regeneration via their impact on the microbiota. These results highlight H. glaberrima as a promising model to study the importance of the microbiota during organ regeneration.

Abstract

The increased antibiotics usage in biomedical and agricultural settings has been well documented. Antibiotics have now been shown to exert effects outside their purposive use, including effects on physiological and developmental processes. We explored the effect of various antibiotics on intestinal regeneration in the sea cucumber Holothuria glaberrima. For this, holothurians were eviscerated and left to regenerate for 10 days in seawater with different penicillin/streptomycin-based cocktails (100 µg/mL PS) including: 100 µg/mL kanamycin (KPS), 5 µg/mL vancomycin (VPS), and 4 µg/mL (E4PS) or 20 µg/mL (E20PS) erythromycin. Immunohistological and histochemical analyses were performed to analyze regenerative processes, including rudiment size, extracellular matrix (ECM) remodeling, cell proliferation, and muscle dedifferentiation. A reduction in muscle dedifferentiation was observed in all antibiotic-treated animals. ECM remodeling was decreased by VPS, E4PS, and E20PS treatments. In addition, organisms subjected to E20PS displayed a significant reduction in the size of their regenerating rudiments while VPS exposure altered cell proliferation. MTT assays were used to discard the possibility that the antibiotics directly affect holothurian metabolic activity while bacterial cultures were used to test antibiotic effects on holothurian enteric microbiota. Our results demonstrate a negative effect on intestinal regeneration and strongly suggest that these effects are due to alterations in the microbial community.

Use of waste materials to prevent tetracycline antibiotics toxicity on the growth of soil bacterial communities

The increase of concentrations of tetracycline antibiotics in agricultural soils worldwide is of special concern, due to its potential toxic effects on soil bacterial communities. In the present work, the reuse of two waste/by-product materials as soil amendments was tested as a preventive practice for reducing tetracycline antibiotics toxicity in soils. Pine bark (PB), with high percentage of organic carbon, and crushed mussel shell (CMS), a frequent natural liming material, were added to 4 soils in doses 0, 6, 12 and 48 g of by-product per kg^-1 of soil (dry weight) of each one (separately). The soils and soil-waste mixtures were then spiked with tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC). After one day of incubation, the bacterial growth was estimated in soils and soil-mixtures using the leucine incorporation technique. The addition of PB to the soils showed two different behaviors, depending on the antibiotics. The toxicity of TC and OTC decreased with the addition of PB (toxicities going from 6 to 25% and from 5 to 36%, respectively). However, CTC toxicity did not change, or even increased in response to the PB amendment. Regarding soil amendment with CMS, it was not effective to prevent the toxicity of any of the three antibiotics studied.

Identification of the priority antibiotics based on their detection frequency, concentration, and ecological risk in urbanized coastal water

Antibiotics have raised significant concern as emerging pollutants for their increasing consumption, persistent input, and potential threat to ecological environment. Due to low concentrations and various types in coastal water, simultaneous quantification of all kinds of antibiotics is time-consuming and costly. In order to make antibiotic regular monitoring in coastal water possible, identifying the priority antibiotics in the environment is essential. Here, a method for screening the priority antibiotics in coastal water was proposed, considering individual antibiotic concentration, the positive correlation between individual and total antibiotic concentration, the detection frequency, and obvious ecological risk. Taking coastal water of the East China Sea as an example, on a list of 77 target antibiotics, 7 (SMX, TMP, SCP, SMP, CNX, ATM, and ETM) and 4 (SMX, SCP, SMP, and CNX) antibiotics were selected to be the priority antibiotics in 2017 and 2018, respectively. Furthermore, the 4 priority antibiotics in 2018 were all involved in the 7 priority antibiotics in 2017. The sum of the priority antibiotic concentrations accounted for 0.8% and 23.2% of total antibiotic concentrations, and the sum of their RQ accounted for 69.2% and 66.8% of total RQ values in 2017 and 2018, respectively. Among the above 7 priority antibiotics, ATM is mainly used in human clinical, SMX, SCP, and SMP are mainly consumed in veterinary medicine, TMP, CNX, and ETM are commonly used for humans and animals. The proposed method might provide an important reference for the monitoring and management of antibiotic pollution in coastal water.

Macro, colloidal and nanobiochar for oxytetracycline removal in synthetic hydrolyzed human urine

Macro (BC), colloidal (CBC) and nanobiochar (NBC) were examined for the particle size effect for adsorptive removal of oxytetracycline (OTC) and co-occurring nutrients, which are present in synthetic hydrolyzed human urine. The surface morphologies and functionality of biochars were characterized using Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) specific surface area and Fourier Transform Infra-Red (FTIR) Spectroscopy. Experiments for the removal of OTC were performed at the natural pH (pH 9.0) of hydrolyzed human urine using solid-solutions of 3 types of chars (1 g/L) with a contact time of 5 h, at initial OTC concentration of 50 mg/L where isotherm experiments were investigated with OTC concentrations from 25 to 1000 mg/L. The highest maximum adsorption capacity of 136.7 mg/g was reported for CBC, while BC reported slightly low value (129.34 mg/g). Interestingly, NBC demonstrated a two-step adsorption process with two adsorption capacities (16.9 and 113.2 mg/g). Colloidal biochar depicted the highest adsorption for NH₄⁺, PO₄^3-, and SO₄^2- nutrients. All 3 types of chars showed strong retention with a poor desorption (6% in average) of OTC in synthetic hydrolyzed urine medium. CBC and NBC demonstrated both physisorption and chemisorption, whereas the OTC removal by BC was solely via physisorption. Nevertheless, CBC biochar demonstrated the best performance in adsorptive removal of OTC and nutrients in hydrolyzed human urine and its capability towards wastewater treatment. As the removal of nutrients were low, the treated urine can possibly be used as a safe fertilizer.

A review of the toxicity in fish exposed to antibiotics

Antibiotics are widely used in the treatment of human and veterinary diseases and are being used worldwide in the agriculture industry to promote livestock growth. However, a variety of antibiotics that are found in aquatic environments are toxic to aquatic organisms. Antibiotics are not completely removed by wastewater treatment plants and are therefore released into aquatic environments, which raises concern about the destruction of the ecosystem owing to their non-target effects. Since antibiotics are designed to be persistent and work steadily in the body, their chronic toxicity effects have been studied in aquatic microorganisms. However, research on the toxicity of antibiotics in fish at the top of the aquatic food chain is relatively poor. This paper summarizes the current understanding of the reported toxicity studies with antibiotics in fish, including zebrafish, to date. Four antibiotic types; quinolones, sulfonamides, tetracyclines, and macrolides, which are thought to be genetically toxic to fish have been reported to bioaccumulate in fish tissues, as well as in aquatic environments such as rivers and surface water. The adverse effects of these antibiotics are known to cause damage to developmental, cardiovascular, and metabolic systems, as well as in altering anti-oxidant and immune responses, in fish. Therefore, there are serious concerns about the toxicity of antibiotics in fish and further research and strategies are needed to prevent them in different regions of the world.

Resistance of cyanobacteria Microcystis aeruginosa to erythromycin with multiple exposure

Here we report a set of experiments in which water blooming cyanobacteria Microcystis aeruginosa was repeatedly exposed to erythromycin. Growth inhibition increased with increasing erythromycin concentration (1-150 μg/L) upon first exposure. Maximum inhibition rate (76.06%), occurred under 150 μg/L erythromycin. Moreover, 96-h 50% effective concentration (EC₅₀) was 22.97 μg/L, indicating that the growth of M. aeruginosa was affected by erythromycin under common environmental concentrations. Photosynthesis was hindered by chlorophyll and photosystem II limitations. Malondialdehyde, reactive oxygen species, and superoxide dismutase contents increased significantly under certain concentrations of erythromycin, but superoxide dismutase was suppressed by 150 μg/L erythromycin. Synthesis of intracellular and extracellular microcystins was promoted by 10-60 and by 20-60 μg/L erythromycin, respectively, but both were inhibited by 100-150 μg/L. Principal component analysis and Pearson's correlation revealed the accumulation of reactive oxygen species as the dominant mechanism of erythromycin toxicity to cells. M. aeruginosa repeatedly subjected to erythromycin exposure showed obvious resistance against the antibiotic, especially when treated twice with 60 μg/L erythromycin. The 96-h EC₅₀ was 81.29 μg/L. As compared to the first exposure to erythromycin, photosynthetic and antioxidant activities increased, while growth inhibition and oxidation stress decreased upon multiple exposures. Production and release of microcystins were enhanced by repeated exposure to the antibiotic. Thus, erythromycin persistence in water should be examined, as repeated exposure may lead to serious environmental and human health hazards.

The Effect of Acute Erythromycin Exposure on the Swimming Ability of Zebrafish (Danio rerio) and Medaka (Oryzias latipes)

Erythromycin is a widely used antibiotic, and erythromycin contamination may pose a threat to aquatic organisms. However, little is known about the adverse effects of erythromycin on swimming ability. To quantify erythromycin-induced damage to fish swimming ability, Oryzias latipes and Danio rerio were acutely exposed to erythromycin. The swimming ability of the experimental fish was measured after exposure to varying doses of erythromycin (2 µg/L, 20 µg/L, 200 µg/L, and 2 mg/L) for 96 h. Burst speed (U_burst) and critical swimming speed (U_crit) of experimental fish significantly decreased. In addition, gene expression analysis of O. latipes and D. rerio under erythromycin treatment (2 mg/L) showed that the expression of genes related to energy metabolism in the muscle was significantly reduced in both species of fish. However, the gene expression pattern in the head of the two species was differentially impacted; D. rerio showed endocrine disruption, while phototransduction was impacted in O. latipes. The results of our study may be used as a reference to control erythromycin pollution in natural rivers.

Effect of molecular structure on the adsorption affinity of sulfonamides onto CNTs: Batch experiments and DFT calculations

In order to investigate the adsorption behaviors of sulfonamides onto hydroxylated multi - walled carbon nanotubes (CNTs) with a porous structure and large specific surface area, six typical sulfonamides including sulfanilamide (SAM), sulfamerazine (SMR), sulfadimethoxine (SMX), sulfadiazine (SDZ), sulfamethazine (SMT) and sulfametoxydiazine (SMD) were selected to be adsorbed respectively on CNTs, and in the same time the structural parameters of the six sulfonamides molecules were calculated according to the density functional theory (DFT). Based upon above mentioned experiments and the structural parameters, the quantitative correlation between the structural parameters of sulfonamides molecules and their adsorption affinity (e.g. adsorption capacity and adsorption rate constant) onto CNTs was established, respectively. The adsorption data of sulfonamides fitted well with the pseudo - second - order kinetic model and the Langmuir isotherm model. The order of both pseudo - second - order kinetic constant and maximum adsorption capacity of the six sulfonamides were SAM < SMR < SMX < SDZ < SMT < SMD. The frontier molecular orbital energy (E_HOMO) and dipole moment (μ) could be used as indicators for the adsorption affinity of sulfonamides onto CNTs. Accordingly, the possible adsorption mechanism was proposed.

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.

Hysterical tetracycline in intensive poultry farms accountable for substantial gene resistance, health and ecological risk in Egypt- manure and fish

Although the poultry production sector plays a key role in sustaining the majority of animal protein demand in Egypt, the deleterious effects of widespread antibiotic resistance on health and environment are currently not well recognized. Litter and dropping samples from broiler and layer poultry farms as well as, tilapia samples from the Nile River and aquaculture farms were collected from Upper Egypt. Samples were extracted and examined for tetracycline residues [tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DC)] using HPLC. In addition, tetracycline resistance genes [tet (M), tet (W), tet (Q) and tet (G)] were screened from pooled intestinal contents collected from twelve broiler farms in Upper Egypt. The antibiotic resistance genes results revealed that tet (W) was confirmed to be expressed in all intestinal samples. In contrast, tet (Q) and tet (M) were detected only in 42% and 17% of the samples, respectively. CTC and OTC were the antimicrobial compounds with the highest concentrations in poultry litter and droppings, with concentrations of 6.05 and 2.47 μg g^-1 (CTC) and 5.9 and 1.33 μg g^-1 (OTC), respectively. However, the concentrations of DC were significantly higher than those of the other compounds in both aquaculture and Nile River tilapia. The tetracycline residue levels in aquaculture tilapia were significantly higher than those in Nile River tilapia. The hazard quotients (HQs) exceeded 1 for OTC, CTC and DC, which highlights the great risk of using broiler litter to fertilize agricultural land. Moreover, the presence of DC and CTC indicates that consumption of aquaculture tilapia poses a considerable health risk. Therefore, poultry litter or droppings containing tetracycline residues and tet resistance determinants used for aquaculture or as farmland fertilizers could be major sources of antibiotic resistance in fish, humans and environment.

Probabilistic ecological risk assessment of heavy metals using the sensitivity of resident organisms in four Korean rivers

The environment has been continuously exposed to heavy metals by various routes, from both natural and artificial sources. In particular, heavy metals in water can affect aquatic organisms adversely, even at very low concentrations, and can lead to the disturbance of the ecosystem balance and biodiversity. Ecological risk assessments are conducted to protect the environment from such situations, primarily by deriving the predicted no-effect concentration (PNEC) from the species sensitivity distribution (SSD). This study developed the SSDs based on the species living in Korean freshwater for four heavy metals including cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). The species compositions of the SSDs were examined, and three types of PNECs were derived by applying different assessment factors (AF). In addition, the occurrence and concentrations of heavy metals in Korean rivers were investigated, and the ecological risk assessment was carried out to compare the SSDs with the environmental concentrations. The SSDs were developed using a sufficient number of species, but the missing data of plants and insects provided an incomplete species composition. The results show that Cd and Pb in the environmental concentrations of rivers would not cause any risk to aquatic organisms from the derived PNEC. However, some organisms might be adversely affected by the concentrations of Zn, and a small amount of risk was expected under the conservative PNEC. The distribution of Cu in the rivers was not considered to be safe for aquatic organisms because the average environmental concentrations potentially affected the proportion of the SSD, and the environmental concentrations exceeded the PNECs. The concentrations of Cu and Zn in industrial waters indicated a considerable risk to aquatic organisms, and the probability of exceeding the PNECs appeared to be quite high. Therefore, this study indicates that additional actions and parallel field studies are required based on the risk posed to aquatic organisms by Cu and Zn in four Korean rivers.

Graphene modified anatase/titanate nanosheets with enhanced photocatalytic activity for efficient degradation of sulfamethazine under simulated solar light

Graphene modified anatase/titanate nanosheets (G/A/TNS) synthesized through hydrothermal treatment were used for solar-light-driven photocatalytic degradation of a typical pharmaceutically active compound, sulfamethazine (SMT). The optimal material was synthesized with 0.5 wt% of graphene loading (G/A/TNS-0.5), which could efficiently degrade 96.1% of SMT at 4 h. G/A/TNS-0.5 showed enhanced photocatalytic activity compared with the neat anatase and unmodified anatase/titanate nanosheets (A/TNS). UV-vis diffuse reflection spectra indicated that G/A/TNS-0.5 had a lower energy band gap (E_g) of 2.8 eV than A/TNS (3.1 eV). The grafted graphene acted as an electron transfer mediator after photoexcitation, resulting in inhibition on rapid recombination of electron-hole pairs. More importantly, architecture of graphene and titanate nanosheets both with two-dimensional structures greatly facilitated the photoexcited electron transfer. •OH and ¹O₂ were the primary reactive oxygen species (ROS) to SMT degradation. Fukui index (f^-) derived from density functional theory (DFT) calculation predicted the active sites on SMT molecule, and then SMT degradation pathway was proposed by means of intermediates identification and theoretical calculation. Furthermore, G/A/TNS-0.5 could be well reused and 90.5% of SMT was also degraded after five runs. The developed new photocatalysts show great potential for degradation of emerging organic contaminants through photocatalysis under solar light.

The Use of Algae and Fungi for Removal of Pharmaceuticals by Bioremediation and Biosorption Processes: A Review

The occurrence and fate of pharmaceuticals in the aquatic environment is recognized as one of the emerging issues in environmental chemistry. Conventional wastewater treatment plants (WWTPs) are not designed to remove pharmaceuticals (and their metabolites) from domestic wastewaters. The treatability of pharmaceutical compounds in WWTPs varies considerably depending on the type of compound since their biodegradability can differ significantly. As a consequence, they may reach the aquatic environment, directly or by leaching of the sludge produced by these facilities. Currently, the technologies under research for the removal of pharmaceuticals, namely membrane technologies and advanced oxidation processes, have high operation costs related to energy and chemical consumption. When chemical reactions are involved, other aspects to consider include the formation of harmful reaction by-products and the management of the toxic sludge produced. Research is needed in order to develop economic and sustainable treatment processes, such as bioremediation and biosorption. The use of low-cost materials, such as biological matrices (e.g., algae and fungi), has advantages such as low capital investment, easy operation, low operation costs, and the non-formation of degradation by-products. An extensive review of existing research on this subject is presented.

Optimization of screening-level risk assessment and priority selection of emerging pollutants - The case of pharmaceuticals in European surface waters

Pharmaceuticals in surface waters have raised significant concern in recent years for their potential environmental effects. This study identified that at present a total of 477 substances (including 66 metabolites and transformation products) have been analyzed in European surface waters. Around 60% (284) of these compounds belonging to 16 different therapeutic groups were positively detected in one or more of 33 European countries. To conveniently and effectively prioritize potential high-risk compounds, an optimized method that considers the frequency of concentrations above predicted no effects levels was developed on the basis of the traditional method, and it was then used to identify and screen candidate priority pollutants in European surface waters. The results proved the feasibility and advantages of the optimized method. Pharmaceuticals detected in European surface waters were classified into 5 categories (high, moderate, endurable, negligible and safe) depending on their potential environmental effects and the distribution of pharmaceuticals. Circa 9% (45 out of 477) analyzed compounds showed a potential environmental risk to aquatic ecosystems. Among these 45 compounds, 12 compounds were indicated to have high environmental risk in aquatic environments, while 17 and 7 compounds showed moderate and small-scale environmental risks, respectively.

Carbon-based materials as adsorbent for antibiotics removal: Mechanisms and influencing factors

With the development of the removal of organic pollutants in the soil and water environment, antibiotics have been considered as emerging pollutants and received considerable attention among the scientific community. Thus, there is a need for an effective, economical, fast, operational feasible and environmental-friendly technology to remove antibiotics. Adsorption technology would be one of the most promising option on the basis that it best meets the criteria we set out above. From the most primitive activated carbon to the most innovative modified biochar, carbon-based materials have played a significant role in the adsorption process of antibiotics all the time. This paper reviews the adsorption behavior of some representative antibiotics (e.g., chloramphenicols, sulfonamides, tetracyclines, flouroquinolones) over various carbonaceous materials (i.e., activated carbon, carbon nanotubes, graphene, and biochar). Nevertheless, in addition to the structural characteristics and adsorption capacities of carbon-based materials, a special emphasis was placed on the underlying adsorption mechanisms and roles of different influencing factors in the adsorption process. Moreover, the knowledge gaps and research challenges have been highlighted, including design and optimization of the carbonaceous materials for antibiotics adsorption.

Pharmaceutical residues in streams near concentrated animal feeding operations of Korea - Occurrences and associated ecological risks

Concentrated animal feeding operations (CAFOs) have been suggested to be the most significant source of pharmaceutical release into the environment. However, limited information is available on the occurrence of veterinary pharmaceutical residues and the associated ecological risks to the aquatic environment near CAFO areas. In this study, ten commonly used veterinary antibiotics, including sulfonamides, tetracyclines, and cephalosporins, along with three analgesics, were measured in water samples collected from the streams that run near two CAFOs in Korea in 2013 (n = 16) and 2014 (n = 10). In addition, the associated ecological risks were estimated by calculating risk quotient. The pharmaceuticals were detected in a higher amount in the samples collected downstream from the CAFO than in those collected upstream. Acetaminophen, sulfamethazine, sulfathiazole, and oxytetracycline were detected at maximum concentrations of 38.8 μg/L, 21.3 μg/L, 17.4 μg/L, and 16.9 μg/L, respectively. Relatively higher concentrations of pharmaceuticals were observed in locations adjacent to the CAFO and the downstream area, suggesting the influence of the CAFO. Except for acetaminophen, lower concentrations of the target pharmaceuticals were detected in the samples collected during the high-flow season. The concentrations of most of the target pharmaceuticals exceeded the risk quotient of one, suggesting potential ecological effects in the areas affected by CAFOs. Our observations show that the water environment near a CAFO could be heavily affected by veterinary pharmaceuticals and analgesic drugs that are also frequently used among humans. Hence, the ecological consequences of pharmaceutical residues in the water bodies near CAFOs warrant further investigation.

Impact of erythromycin on a non-target organism: Cellular effects on the freshwater microalga Pseudokirchneriella subcapitata

The increasing and indiscriminate use of antibiotics is the origin of their introduction in aquatic systems through domestic and livestock effluents. The occurrence of erythromycin (ERY), a macrolide antibiotic, in water bodies raises serious concerns about its potential toxic effect in aquatic biota (non-target organisms), particularly in microalgae, the first organisms in contact with aquatic contaminants. This study aimed to evaluate the possible toxic effects of ERY on relevant cell targets of the freshwater microalga Pseudokirchneriella subcapitata. Algal cells incubated with significant environmental ERY concentrations presented disturbance of the photosynthetic apparatus (increased algal autofluorescence and reduction of chlorophyll a content) and mitochondrial function (hyperpolarization of mitochondrial membrane). These perturbations can apparently be attributed to the similarity of the translational machinery of these organelles (chloroplasts and mitochondria) with the prokaryotic cells. P. subcapitata cells treated with ERY showed a modification of metabolic activity (increased esterase activity) and redox state (alteration of intracellular levels of reactive oxygen species and reduced glutathione content) and an increased biovolume. ERY induced an algistatic effect: reduction of growth rate without loss of cell viability (plasma membrane integrity). The present study shows that chronic exposure (72 h), at low (μg L^-1) ERY concentrations (within the range of concentrations detected in surface and ground waters), induce disturbances in the physiological state of the alga P. subcapitata. Additionally, this work alerts to the possible negative impact of the uncontrolled use of ERY on the aquatic systems.

Assessment of toxic effects of the antibiotic erythromycin on the marine fish gilthead seabream (Sparus aurata L.) by a multi-biomarker approach

Erythromycin (ERY) is one of the most common antibiotics used in human and veterinary practices, leading to ubiquitous environmental distribution and possible toxicity to non-target organisms. The purpose of this study was to determine sub-lethal effects of ERY towards the marine fish Sparus aurata (gilthead seabream). S. aurata were acutely (0.3-323 μg/L, 96 h) and chronically (0.7-8.8 μg/L, 28 d) exposed to ERY. Detoxification [7-ethoxyresorufin O-deethylase (EROD), glutathione S-transferases (GSTs), uridine-diphosphate-glucuronosyltransferase (UGT)], oxidative stress [catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GRed)], lipid peroxidation [thiobarbituric acid reactive substances - (TBARS)], genotoxicity [genetic damage index (GDI) and erythrocytic nuclear abnormalities (ENAs)], neurotransmission [acetylcholinesterase (AChE)] and energy metabolism [lactate dehydrogenase (LDH)] biomarkers were evaluated. Results showed that ERY did not promote significant effects in detoxification biomarkers, but induced slight pro-oxidative effects (decrease of GPx activity in the liver after acute exposure and an increase in gills after chronic exposure; and an increase of hepatic GRed activity following chronic exposure). There was a significant decrease in TBARS after chronic exposure, which contradicts a full scenario of oxidative stress. In terms of genotoxicity, both ERY exposures caused only a significant increase of GDI. Neurotransmission and energy metabolism were not also affected by ERY. Although few toxic effects of ERY have been previously documented (involving different metabolic pathways, as tested in this work), these were mainly observed for freshwater species. These findings suggest low vulnerability of S. aurata to ERY at levels close to the ones found in the wild.

Toxicity of erythromycin to Oncorhynchus mykiss at different biochemical levels: detoxification metabolism, energetic balance, and neurological impairment

During the last decades, the presence of antibiotics in different aquatic compartments has raised increasing interest and concern, since these compounds are usually persistent and bioactive pseudo pollutants. Erythromycin (ERY) is a macrolide antibiotic, prescribed for human and veterinary medicines but also used in aquaculture and livestock production. Taking into account the recorded environmental levels of ERY, its toxicity to non-target organisms has become a still poorly studied issue, particularly in fish. In this sense, this study investigated the acute and chronic effects of realistic levels of ERY on Oncorhynchus mykiss (rainbow trout), namely, through the quantification of the activity of enzymes involved in different biochemical pathways, such as detoxification (phase I-7-ethoxyresorufin O-deethylase (EROD); phase II-glutathione S-transferases (GSTs), uridine-diphosphate-glucuronosyltransferases (UGTs)), neurotransmission (acetylcholinesterase (AChE)), and energy production (lactate dehydrogenase (LDH)). Both types of exposure caused significant increases in EROD activity in liver of O. mykiss; an increase in GST activity in gills after chronic exposure was also observed. UGT branchial activity was significantly depressed, following the long-term exposure. Thus, EROD, GST, and UGT enzymatic forms seem to be involved in the biotransformation of ERY. In terms of neurotransmission and preferential pathway of energy homeostasis, the exposed organisms appear not to have been affected, as there were no significant alterations in terms of AChE and LDH activities, respectively. The here-obtained data suggest that the observed alterations in terms of detoxification enzymes may have prevented the establishment of a set of toxic responses, namely, neurotoxic and metabolic disorders.

Assessment of Three Antimicrobial Residue Concentrations in Broiler Chicken Droppings as a Potential Risk Factor for Public Health and Environment

Tetracyclines, sulfonamides and amphenicols are broad spectrum antimicrobial drugs that are widely used in poultry farming. However, a high proportion of these drugs can be excreted at high concentrations in droppings, even after the end of a therapy course. This work intended to assess and compare concentrations of florfenicol (FF), florfenicol amine (FFa), chlortetracycline (CTC), 4-epi-chlortetracycline (4-epi-CTC), and sulfachloropyridazine (SCP) in broiler chicken droppings. To this end, 70 chickens were housed under controlled environmental conditions, and assigned to experimental groups that were treated with therapeutic doses of either 10% FF, 20% CTC, or 10% SCP. Consequently, we implemented and designed an in-house validation for three analytical methodologies, which allowed us to quantify the concentrations of these three antimicrobial drugs using liquid chromatography coupled to mass spectrometry (LC-MS/MS). Our results showed that FF and FFa concentrations were detected in chicken droppings up to day 10 after ceasing treatment, while CTC and 4-epi-CTC were detected up to day 25. As for SCP residues, these were detected up to day 21. Noticeably, CTC showed the longest excretion period, as well as the highest concentrations detected after the end of its administration using therapeutic doses.