Assessment of the Risks of Mixtures of Major Use Veterinary Antibiotics in European Surface Waters

Toxicity of selected pharmaceuticals and their mixtures to the aquatic indicators Daphnia magna and Aliivibrio fischeri

Despite the benefits derived from the use of pharmaceuticals, these compounds are currently considered contaminants of emerging concern because of their presence and persistence in the environment. This study aimed to determine the toxicity of 27 pharmaceuticals and the interaction effects of binary mixtures of selected compounds towards two model organisms: the microcrustacean Daphnia magna and the bacterium Aliivibrio fischeri (Microtox test). Six compounds, namely polymyxin B, polymyxin E, fluoxetine, diphenhydramine, clenbuterol and ketoprofen exhibited moderate toxicity towards D. magna. Additionally, three compounds (cefotaxime, polymyxin B, polymyxin E) also showed a moderate toxic effect on A. fischeri. The comparison of such results with model estimations showed inaccuracy in the predicted data, highlighting the relevance of experimental ecotoxicological assays. The assayed mixtures contained four selected drugs of high-hazard according to their reported concentrations in wastewater and surface water (diphenhydramine, trimethoprim, ketoprofen, and fluoxetine); data revealed interactions only in the fluoxetine-containing mixtures for D. magna, while all mixtures showed interactions (mostly synergistic) for Microtox. Chronic effects on the reproduction of D. magna were observed after exposure to fluoxetine and diphenhydramine, although higher sensitivity was determined for the latter, while the mixture of these compounds (which showed acute synergy in both models) also affected the reproduction patterns. Nonetheless, all the effects described at the acute or chronic level (for individual compounds or mixtures) were determined at concentrations higher than commonly reported at environmental levels. This work provides valuable ecotoxicological information for the risk assessment of pharmaceuticals and their mixtures in the environment.

Spontaneous interactions between typical antibiotics and soil enzyme: Insights from multi-spectroscopic approaches, XPS technology, molecular modeling, and joint toxic actions

A large amount of antibiotics enters the soil environment and accumulates therein as individuals and mixtures, threatening the soil safety. However, there is little information regarding the influence of single and mixed antibiotics on key soil proteins at molecular level. In this study, setting sulfadiazine (SD) and tetracycline hydrochloride (TC) as the representative antibiotics, the interactions between these agents and α-amylase (an important hydrolase in soil carbon cycle) were investigated through multi-spectroscopic approaches, X-ray photoelectron spectrometry, and molecular modeling. It was found that both SD and TC spontaneously bound to α-amylase with 1:1 stoichiometry mainly via forming stable chemical bonds. The interactions altered the polarity of aromatic amino acids, protein backbone, secondary structure, hydrophobicity and activity of α-amylase. The SD-TC mixtures were designed based on the direct equipartition ray to comprehensively characterize the possible concentration distribution, and interactive effects indicated that the mixtures antagonistically impacted α-amylase. These findings reveal the binding characteristics between α-amylase and typical antibiotics, which probably influence the ecological functions of α-amylase in soil. This study clarifies the potential harm of antibiotics on soil functional enzyme, which is significant for the environmental risk assessment of antibiotics and their mixtures.

Sustainable application of modified Luffa cylindrica biomass for removal of trimethoprim in water by adsorption with process optimization

The present study describes a set of methodological procedures (seldom applied together), including (i) development of an alternative adsorbent derived from abundant low-cost plant biomass; (ii) use of simple low-cost biomass modification techniques based on physical processing and chemical activation; (iii) design of experiments (DoE) applied to optimize the removal of a pharmaceutical contaminant from water; (iv) at environmentally relevant concentrations, (v) that due to initial low concentrations required determination by ultra-performance liquid phase chromatography coupled to mass spectrometry (UPLC-MS/MS). A central composite rotational design (CCRD) was employed to investigate the performance of vegetable sponge biomass (Luffa cylindrica), physically processed (crushing and sieving) and chemically activated with phosphoric acid, in the adsorption of the antibiotic trimethoprim (TMP) from water. The optimized model identified pH as the most significant variable, with maximum drug removal (91.1 ± 5.7%) achieved at pH 7.5, a temperature of 22.5 °C, and an adsorbent/adsorbate ratio of 18.6 mg µg-1. The adsorption mechanisms and surface properties of the adsorbent were examined through characterization techniques such as scanning electron microscopy (SEM), point of zero charge (pHpzc) measurement, thermogravimetric analysis (TGA), specific surface area, and Fourier-transform infrared spectroscopy (FTIR). The best kinetic fit was obtained by the Avrami fractional-order model. The hypothesis of a hybrid behavior of the adsorbent was suggested by the equilibrium results presented by the Langmuir and Freundlich models and reinforced by the Redlich-Peterson model, which achieved the best fit (R2 = 0.982). The thermodynamic study indicated an exothermic, spontaneous, and favorable process. The maximum adsorption capacity of the material was 2.32 × 102 µg g-1 at an equilibrium time of 120 min. Finally, a sustainable and promising adsorbent for the polishing of aqueous matrices contaminated by contaminants of emerging concern (CECs) at environmentally relevant concentrations is available for future investigations.

Advances in identifying and managing emerging contaminants in aquatic ecosystems: Analytical approaches, toxicity assessment, transformation pathways, environmental fate, and remediation strategies

Emerging contaminants (ECs) are increasingly recognized as threats to human health and ecosystems. This review evaluates advanced analytical methods, particularly mass spectrometry, for detecting ECs and understanding their toxicity, transformation pathways, and environmental distribution. Our findings underscore the reliability of current techniques and the potential of upcoming methods. The adverse effects of ECs on aquatic life necessitate both in vitro and in vivo toxicity assessments. Evaluating the distribution and degradation of ECs reveals that they undergo physical, chemical, and biological transformations. Remediation strategies such as advanced oxidation, adsorption, and membrane bioreactors effectively treat EC-contaminated waters, with combinations of these techniques showing the highest efficacy. To minimize the impact of ECs, a proactive approach involving monitoring, regulations, and public education is vital. Future research should prioritize the refining of detection methods and formulation of robust policies for EC management.

More movement with manure: increased mobility of erythromycin through agricultural soil in the presence of manure

Antibiotic residues in the environment threaten soil and aquatic organisms and human and livestock health through the building of antimicrobial resistance. Manure spreading associated with animal agriculture is one source of environmental antibiotic residues. To better understand the risk of contamination, we studied the adsorption of erythromycin, a model macrolide antibiotic used across human and animal medicine. We conducted a series of equilibrium batch experiments to determine the kinetics and extent of adsorption and a continuous-flow column adsorption experiment to observe non-equilibrium adsorption patterns. We determined that the adsorption equilibration time to soil was approximately 72 h in our batch experiments. Erythromycin adsorbed to soil relatively strongly (K = 8.01 × 10-2 L/mg; qmax = 1.53 × 10-3 mg/mg), adsorbed to the soil in the presence of manure with less affinity (K = 1.99 × 10-4 L/mg) at a soil: manure ratio of 10:1 by mass, and did not adsorb to manure across the solid ratios tested. We observed multi-phased adsorption of erythromycin to the soil during the non-equilibrium column experiment, which was largely absent from the treatments with both soil and manure present. These results suggest that erythromycin is more mobile in the environment when introduced with manure, which is likely the largest source of agriculturally sourced environmental antibiotics.

Effects of Antibiotic Resistance Genes and Antibiotics on the Transport and Deposition Behaviors of Bacteria in Porous Media

Antibiotics present in the natural environment would induce the generation of antibiotic-resistant bacteria (ARB), causing great environmental risks. The effects of antibiotic resistance genes (ARGs) and antibiotics on bacterial transport/deposition in porous media yet are unclear. By using E. coli without ARGs as antibiotic-susceptible bacteria (ASB) and their corresponding isogenic mutants with ARGs in plasmids as ARB, the effects of ARGs and antibiotics on bacterial transport in porous media were examined under different conditions (1-4 m/d flow rates and 5-100 mM NaCl solutions). The transport behaviors of ARB were comparable with those of ASB under antibiotic-free conditions, indicating that ARGs present within cells had negligible influence on bacterial transport in antibiotic-free solutions. Interestingly, antibiotics (5-1000 μg/L gentamicin) present in solutions increased the transport of both ARB and ASB with more significant enhancement for ASB. This changed bacterial transport induced by antibiotics held true in solution with humic acid, in river water and groundwater samples. Antibiotics enhanced the transport of ARB and ASB in porous media via different mechanisms (ARB: competition of deposition sites; ASB: enhanced motility and chemotaxis effects). Clearly, since ASB are likely to escape sites containing antibiotics, these locations are more likely to accumulate ARB and their environmental risks would increase.

Biosorption and biotransformation behaviours of veterinary antibiotics under aerobic livestock wastewater treatment processes

To study the fate of veterinary antibiotics released from swine wastewater treatment plants (SWTP), 10 antibiotics were investigated in each unit of a local SWTP periodically. Over a 14-month period of field investigation into target antibiotics, it was confirmed that tetracycline, chlortetracycline, sulfathiazole, and lincomycin were used in this SWTP, with their presence observed in raw manure. Most of these antibiotics could be effectively treated by aerobic activated sludge, except for lincomycin, which was still detected in the effluent, with a maximum concentration of 1506 μg/L. In addition, the potential for removing antibiotics was evaluated using lab-scale aerobic sequencing batch reactors (SBRs) that were dosed with high concentrations of antibiotics. The SBR results, however, showed that both sulfonamides and macrolides, as well as lincomycin, can achieve 100% removal in lab-scale aerobic SBRs within 7 days. This reveals that the potential removal of those antibiotics in field aeration tanks can be facilitated by providing suitable conditions, such as adequate dissolved oxygen, pH, and retention time. Furthermore, the biosorption of target antibiotics was also confirmed in the abiotic sorption batch tests. Biotransformation and hydrolysis were identified as the dominant mechanism for removing negatively charged sulfonamides and positively charged antibiotics (macrolides and lincomycin) in SBRs. This is due to their relatively low sorption affinity (resulting in negligible to 20% removal) onto activated sludge in abiotic sorption tests. On the other hand, tetracyclines exhibited significant sorption behavior both onto activated sludge and onto soluble organic matters in swine wastewater supernatant, accounting for 70%-91% and 21%-94% of removal within 24 h, respectively. S-shape sorption isotherms with saturation were observed when high amounts of tetracyclines were spiked into sludge, with equilibrium concentrations ranging from 0.4 to 65 mg/L. Therefore, the sorption of tetracyclines onto activated sludge was governed by electrostatic interaction rather than hydrophobic partition. This resulted in a saturated sorption capacity (Q_max) of 17,263 mg/g, 1637 mg/g, and 641.7 mg/g for OTC, TC, and CTC, respectively.

Synergistic Signal Amplification-Initiated Innovative Self-Powered Photoelectrochemical Aptasensing: An Ingenious Photocathode Activated by the High-Light-Harvesting Photoanode

Exploiting ingenious photoelectrodes and innovative signal amplification strategies has the potential to achieve high sensitivity in self-powered cathodic photoelectrochemical (PEC) analysis. In this work, a novel self-powered PEC sensing platform was constructed by integrating a synergistic signal amplification of an ingenious photocathode with a high light-harvesting photoanode. In the dual photoelectrode-based PEC system, the amplified photocurrent signals were induced by a synergistic enhancement: (1) the photocurrent of the BiOBr photocathode was improved by the incorporation of nitrogen-doped graphene; (2) the photocurrent of the self-powered sensor was activated by the high-light-harvesting Bi₂S₃-C₃N₄ photoanode. Subsequently, the rational mechanism for synergistic signal amplification was investigated. For the construction of the sensing interface, an aptamer was introduced as the recognition element to specifically capture the streptomycin (STR) target. Under optimal conditions, the constructed self-powered aptasensor has the merits of good linear range (1 × 10^-11 to 5 × 10^-7 M), acceptable limit of detection (1.18 × 10^-12 M), and excellent stability and selectivity for STR detection. Additionally, the proposed self-powered aptasensor showed acceptable accuracy for the detection of STR in water. Hopefully, this might stimulate more interest in designing and constructing novel platforms for exquisite photocathodic monitoring of various contaminants in the environment.

Combined toxicity of erythromycin and roxithromycin and their removal by Chlorella pyrenoidosa

The ecological effects of antibiotics in surface water have attracted increasing research attention. In this study, we investigated the combined ecotoxicity of erythromycin (ERY) and roxithromycin (ROX) on the microalgae, Chlorella pyrenoidosa, and the removal of ERY and ROX during the exposure. The calculated 96-h median effect concentration (EC₅₀) values of ERY, ROX, and their mixture (2:1 w/w) were 7.37, 3.54, and 7.91 mg∙L^-1, respectively. However, the predicted EC₅₀ values of ERY+ROX mixture were 5.42 and 1.51 mg∙L^-1, based on the concentration addition and independent action models, respectively. This demonstrated the combined toxicity of ERY+ ROX mixture showed an antagonistic effect on Chlorella pyrenoidosa. During the 14-d culture, low-concentration (EC₁₀) treatments with ERY, ROX, and their mixture caused the growth inhibition rate to decrease during the first 12 d and increase slightly at 14 d. In contrast, high-concentration (EC₅₀) treatments significantly inhibited microalgae growth (p < 0.05). Changes in the total chlorophyll contents, SOD and CAT activities, and MDA contents of microalgae suggested that individual treatments with ERY and ROX induced higher oxidative stress than combined treatments. After the 14-d culture time, residual Ery in low and high concentration Ery treatments were 17.75% and 74.43%, and the residual Rox were 76.54% and 87.99%, but the residuals were 8.03% and 73.53% in ERY+ ROX combined treatment. These indicated that antibiotic removal efficiency was higher in combined treatments than that in individual treatments, especially at low concentrations (EC₁₀). Correlation analysis suggested that there was a significant negative correlation between the antibiotic removal efficiency of C. pyrenoidosa and their SOD activity and MDA content, and the enhanced antibiotic removal ability of microalgae benefited from increased cell growth and chlorophyll content. Findings in this study contribute to predicting ecological risk of coexisting antibiotics in aquatic environment, and to improving biological treatment technology of antibiotics in wastewater.

Pharmaceuticals and personal care products (PPCPs) in surface water and fish from three Asian countries: Species-specific bioaccumulation and potential ecological risks

In Asian developing countries, undeveloped and ineffective sewer systems are causing surface water pollution by a lot of contaminants, especially pharmaceuticals and personal care products (PPCPs). Therefore, the risks for freshwater fauna need to be assessed. The present study aimed at: i) elucidating the contamination status; ii) evaluating the bioaccumulation; and iii) assessing the potential risks of PPCP residues in surface water and freshwater fish from three Asian countries. We measured 43 PPCPs in the plasma of several fish species as well as ambient water samples collected from India (Chennai and Bengaluru), Indonesia (Jakarta and Tangerang), and Vietnam (Hanoi and Hoa Binh). In addition, the validity of the existing fish blood-water partitioning model based solely on the lipophilicity of chemicals is assessed for ionizable and readily metabolizable PPCPs. When comparing bioaccumulation factors calculated from the PPCP concentrations measured in the fish and water (BAF_measured) with bioconcentration factors predicted from their pH-dependent octanol-water partition coefficient (BCF_predicted), close values (within an order of magnitude) were observed for 58-91 % of the detected compounds. Nevertheless, up to 110 times higher plasma BAF_measured than the BCF_predicted were found for the antihistamine chlorpheniramine in tilapia but not in other fish species. The plasma BAF_measured values of the compound were significantly different in the three fish species (tilapia > carp > catfish), possibly due to species-specific differences in toxicokinetics (e.g., plasma protein binding and hepatic metabolism). Results of potential risk evaluation based on the PPCP concentrations measured in the fish plasma suggested that chlorpheniramine, triclosan, haloperidol, triclocarban, diclofenac, and diphenhydramine can pose potential adverse effects on wild fish. Results of potential risk evaluation based on the PPCP concentrations measured in the surface water indicated high ecological risks of carbamazepine, sulfamethoxazole, erythromycin, and triclosan on Asian freshwater ecosystems.

Intensive poultry farming: A review of the impact on the environment and human health

Poultry farming is one of the most efficient animal husbandry methods and it provides nutritional security to a significant number of the world population. Using modern intensive farming techniques, global production has reached 133.4 mil. t in 2020, with a steady growth each year. Such intensive growth methods however lead to a significant environmental footprint. Waste materials such as poultry litter and manure can pose a serious threat to environmental and human health, and need to be managed properly. Poultry production and waste by-products are linked to NH₃, N₂O and CH₄ emissions, and have an impact on global greenhouse gas emissions, as well as animal and human health. Litter and manure can contain pesticide residues, microorganisms, pathogens, pharmaceuticals (antibiotics), hormones, metals, macronutrients (at improper ratios) and other pollutants which can lead to air, soil and water contamination as well as formation of antimicrobial/multidrug resistant strains of pathogens. Dust emitted from intensive poultry production operations contains feather and skin fragments, faeces, feed particles, microorganisms and other pollutants, which can adversely impact poultry health as well as the health of farm workers and nearby inhabitants. Fastidious odours are another problem that can have an adverse impact on health and quality of life of workers and surrounding population. This study discusses the current knowledge on the impact of intensive poultry farming on environmental and human health, as well as taking a look at solutions for a sustainable future.

Metabolomic profiles in a green alga (Raphidocelis subcapitata) following erythromycin treatment: ABC transporters and energy metabolism

A recent study showed that erythromycin (ERY) exposure caused hormesis in a model alga (Raphidocelis subcapitata) where the growth was promoted at an environmentally realistic concentration (4 µg/L) but inhibited at two higher concentrations (80 and 120 µg/L), associated with opposite actions of certain signaling pathways (e.g., xenobiotic metabolism, DNA replication). However, these transcriptional alterations remain to be investigated and verified at the metabolomic level. This study uncovered metabolomic profiles and detailed toxic mechanisms of ERY in R. subcapitata using untargeted metabolomics. The metabolomic analysis showed that metabolomic pathways including ABC transporters, fatty acid biosynthesis and purine metabolism were associated with growth promotion in algae treated with 4 µg/L ERY. An overcompensation was possibly activated by the low level of ERY in algae where more resources were reallocated to efficiently restore the temporary impairments, ultimately leading to the outperformance of growth. By contrast, algal growth inhibition in the 80 and 120 µg/L ERY treatments was likely attributed to the dysfunction of metabolomic pathways related to ABC transporters, energy metabolism and metabolism of nucleosides. Apart from binding of ERY to the 50S subunit of ribosomes to inhibit protein translation as in bacteria, the data presented here indicate that inhibition of protein translation and growth performance of algae by ERY may also result from the suppression of amino acid biosynthesis and aminoacyl-tRNA biosynthesis. This study provides novel insights into the dose-dependent toxicity of ERY on R. subcapitata.

Removal of antibiotic resistance genes during livestock wastewater treatment processes: Review and prospects

Antibiotic resistance genes (ARGs) are emerging pollutants that have received extensive attention. Many different types of ARGs exist in livestock wastewater. If not effectively treated, they can threaten animal production, public health and the ecological safety of the surrounding environment. To address the high risk of livestock wastewater contamination by ARGs, the effects of different wastewater treatment processes on ARGs and their influencing factors and mechanisms are reviewed herein. Additionally, the current problems associated with removal of ARGs are discussed, and future research is proposed.

Ecotoxicological effects of human and veterinary antibiotics on water flea (Daphnia magna)

In the present study, we assessed the ecotoxicological effects of selected human and veterinary antibiotics to D. magna. Ecological risk assessment was done by calculating the risk quotients (RQs) of the antibiotics to the species. Results showed that enrofloxacin, a veterinary fluoroquinolone antibiotic, was the most toxic against D. magna with a 48 h EC₅₀ value of 28.59 mg/l. The binary mixture of fluoroquinolones was also more toxic to the species than binary mixtures of macrolides. Fecundity in organisms in negative control was higher than fecundity in organisms exposed to environmentally relevant concentrations of the four antibiotics. Enrofloxacin also has a moderate risk to the species with RQ values of 0.199 and 0.416 in surface waters and wastewaters, respectively. Antibiotics pose a greater ecological risk when present in mixtures in the aquatic environment. Environmental standards for pharmaceuticals should incorporate mixture toxicity data to ensure accurate protection of non-target organisms in polluted environments.

Assessment of the Potential Ecotoxicological Effects of Pharmaceuticals in the World's Rivers

During their production, use, and disposal, active pharmaceutical ingredients (APIs) are released into aquatic systems. Because they are biologically active molecules, APIs have the potential to adversely affect nontarget organisms. We used the results of a global monitoring study of 61 APIs alongside available ecotoxicological and pharmacological data to assess the potential ecotoxicological effects of APIs in rivers across the world. Approximately 43.5% (461 sites) of the 1052 sampling locations monitored across 104 countries in a recent global study had concentrations of APIs of concern based on apical, nonapical, and mode of action-related endpoints. Approximately 34.1% of the 137 sampling campaigns had at least one location where concentrations were of ecotoxicological concern. Twenty-three APIs occurred at concentrations exceeding "safe" concentrations, including substances from the antidepressant, antimicrobial, antihistamine, β-blocker, anticonvulsant, antihyperglycemic, antimalarial, antifungal, calcium channel blocker, benzodiazepine, painkiller, progestin, and lifestyle compound classes. At the most polluted sites, effects are predicted on different trophic levels and on different endpoint types. Overall, the results show that API pollution is a global problem that is likely negatively affecting the health of the world's rivers. To meet the United Nations' Sustainable Development Goals, work is urgently needed to tackle the problem and bring concentrations down to an acceptable level. Environ Toxicol Chem 2022;41:2008-2020. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Bibliometric analysis of microbial sulfonamide degradation: Development, hotspots and trend directions

Microbial sulfonamide degradation (MSD) is an efficient and safe treatment in both natural and engineered ecosystems. In order to systematically understand the research status and frontier trends of MSD, this study employed CiteSpace to conduct a bibliometric analysis of data from the Web of Science (WoS) and the China National Knowledge Infrastructure (CNKI) published from 2000 to 2021. During this time, China, Germany, Spain, the United States and Australia played leading roles by producing numerous high impact publications, while the Chinese Academy of Sciences was the leading research institution in this interdisciplinary research category. The Chemosphere was the top journal in terms of the number of citations. MSD research has gradually progressed from basic laboratory-based experiments to more complex environmental microbial communities and finally to deeper research on molecular mechanisms and engineering applications. Although multi-omics and synthetic community are the key techniques in the frontier research, they are also the current challenges in this field. A summary of published articles shows that Proteobacteria, Gammaproteobacteria, Burkholderiales and Alcaligenaceae are the most frequently observed MSD phylum, class, order and family, respectively, while Bacillus, Pseudomonas and Achromobacter are the top three MSD genera. To our knowledge, this study is the first to investigate the development and current challenges of MSD research, put forward future perspective, and form a relatively complete list of sulfonamide-degrading microorganisms for reference.

Profiling of the spatiotemporal distribution, risks, and prioritization of antibiotics in the waters of Laizhou Bay, northern China

We investigated the spatiotemporal distributions, risks, and prioritization of 15 widely used antibiotics in Laizhou Bay (LZB). Water samples (145) were collected from LZB and its estuaries and analyzed. Twelve antibiotics, with total concentrations of 241-1450 and 69-289 ng L^-1 in estuarine water and seawater, respectively, were detected, with the contributions of norfloxacin, ciprofloxacin, and amoxicillin exceeding 70%. Amoxicillin was firstly determined, which contributed to 20% and 46% of the total antibiotics during summer and spring, respectively. Higher antibiotic concentrations were observed in the sea located adjacent to aquaculture bases and the Yellow River Estuary, which are significantly influenced by mariculture and riverine inputs, respectively. Veterinary antibiotics showed higher total concentrations in summer compared to spring, indicating a higher degree of their usage in mariculture in summer. The antibiotic mixtures posed high risk to algae and low to medium risks to crustaceans and fish. Amoxicillin and norfloxacin were identified as high-risk pollutants. Additionally, amoxicillin and ciprofloxacin showed medium to high resistance development risks. Previous studies on antibiotics in the LZB did not determined amoxicillin and thus underestimated antibiotic contamination, ecological risk, and resistance development risk. Amoxicillin, norfloxacin, and ciprofloxacin should be prioritized in risk management.

The combined toxicity of binary mixtures of antibiotics against the cyanobacterium Microcystis is dose-dependent: insight from a theoretical nonlinear combined toxicity assessment method

The entry of antibiotics into aquatic ecosystems has a serious impact. Antibiotics usually exist as mixtures in natural water bodies. Therefore, it is particularly important to evaluate the mixed toxicity of antibiotic mixtures. The study of the combined toxicity of binary mixtures of antibiotics is the basis for exploring the mixed toxicity of multiple antibiotics. In this investigation, Microcystis aeruginosa (M. aeruginosa) was used as the test organism, and a theoretical nonlinear combined toxicity assessment method was adopted to evaluate the effects of binary mixtures of antibiotics consisting of tetracycline (TC), sulfadiazine (SD), and sulfamethoxazole (SMX) on cell growth, enzymatic activity, and gene expression. The median lethal concentrations of TC, SD, and SMX to M. aeruginosa were 0.52 mg L^-1, 1.65 mg L^-1, and 0.71 mg L^-1, respectively. The results from the theoretical nonlinear combined toxicity assessment method showed that SD + TC was synergistic at low concentrations and antagonistic at high concentrations, while the combinations of SMX + SD and SMX + TC were synergistic. The determination of enzymatic activity and gene expression indicated that the antibiotics could inhibit the growth of M. aeruginosa by destroying the cell membrane structure, inhibiting photosynthesis, impeding the cell division process and the electron transfer process, and destroying the molecular structure of proteins and DNA. Different combinations of antibiotics have different degrees of damage to the antioxidant system and cell membrane self-repair function of M. aeruginosa, which are the reasons for the different combined toxicity effects.

Performance Comparison between the Specific and Baseline Prediction Models of Ecotoxicity for Pharmaceuticals: Is a Specific QSAR Model Inevitable?

Assessing the ecotoxicity of pharmaceuticals is of urgent need due to the recognition of their possible adverse effects on nontarget organisms in the aquatic environment. The reality of ecotoxicity data scarcity promotes the development and application of quantitative structure activity relationship (QSAR) models. In the present study, we aimed to clarify whether a QSAR model of ecotoxicity specifically for pharmaceuticals is needed considering that pharmaceuticals are a class of chemicals with complex structures, multiple functional groups, and reactive properties. To this end, we conducted a performance comparison of two previously developed and validated QSAR models specifically for pharmaceuticals with the commonly used narcosis toxicity prediction model, i.e., Ecological Structure Activity Relationship (ECOSAR), using a subset of pharmaceuticals produced in China that had not been included in the training datasets of QSAR models under consideration. A variety of statistical measures demonstrated that the pharmaceutical specific model outperformed ECOSAR, indicating the necessity of developing a specific QSAR model of ecotoxicity for the active pharmaceutical contaminants. ECOSAR, which was generally used to predict the baseline or the minimum toxicity of a compound, generally underestimated the ecotoxicity of the analyzed pharmaceuticals. This could possibly be because some pharmaceuticals can react through specific modes of action. Nonetheless, it should be noted that 95% prediction intervals spread over approximately four orders of magnitude for both tested QSAR models specifically for pharmaceuticals.

Occurrence and bioaccumulation of sulfonamide antibiotics in different fish species from Hangbu-Fengle River, Southeast China

As a class of synthetic sulfur drugs, sulfonamides (SAs) have been used to treat diseases and promote organism growth. Different concentrations of SAs have been detected in the water environment, which has threatened the ecological environment. In this study, the contamination of 9 SAs in water, sediments, and 8 fish species from the Hangbu-Fengle River, China, were analyzed using UPLC-MS/MS. The total SA concentrations in surface water, sediments, and fish were ND-5.064 ng/L, ND-5.052 ng/g dry weight (d.w.), and ND-1.42 ng/g wet weight (w.w.), respectively. The major compounds were sulfadiazine (SDZ), sulfamerazine (SMZ), and sulfamethoxazole (SMX) in water and fish. The SA levels of in fish from different habitat preferences revealed a spatial difference, with the order of demersal species > pelagic species. Moreover, the SA concentrations were affected by trophic guilds, indicating their decrease in the order of piscivorous fish > omnivorous fish > planktivorous fish > herbivorous fish. The obtained bioaccumulation factors showed that SMZ and SMX have strong bioenrichments in Ophiocephalus argus Cantor and Pelteobagrus fulvidraco. The risk assessment indicated that SAs did not pose significant health threats to the organisms. This research is the first report of SA contamination in the Hangbu-Fenle River, which can provide an important scientific basis for their pollution prevention and ecological risk assessment in the aquatic environment.

Antibiotic residues in the aquatic environment - current perspective and risk considerations

Antimicrobial resistance is a major concern for human and animal health, projected to deteriorate with time and given current trends of antimicrobial usage. Antimicrobial use, particularly in healthcare and agriculture, can result in the release of antimicrobials into surface waters, promoting the development of antibiotic resistance in the environment, and potentially leading to human health risks. This study reviews relevant literature, and investigates current European and Irish antimicrobial usage trends in humans and animals, as well as potential pathways that antibiotics can take into surface waters following use. Reported levels in the aquatic environment are summarized, with particular focus on Ireland. There are relatively few studies examining Irish water bodies or sewage effluent for antibiotic residues, however, five antibiotics, namely azithromycin, ciprofloxacin, clarithromycin, metronidazole, and trimethoprim, have been measured in Irish waters, in concentrations predicted to select for resistance. Numerous isolates of multi-drug resistant bacteria have also been found in water bodies throughout Ireland and Europe. The value of risk assessment methodologies in understanding risks posed by antibiotic residues is reviewed including the advantages and disadvantages of specific approaches. Hazard quotient and bespoke Monte Carlo approaches are predominant risk assessment tools used to examine antimicrobial release and their complex pathways. This study highlights the need for monitoring of antimicrobial releases and the potential for resistance development, persistence and transmission while highlighting the role of risk assessment methodologies in assessing potential human and environmental health impacts.

Ultra-durable, multi-template molecularly imprinted polymers for ultrasensitive monitoring and multicomponent quantification of trace sulfa antibiotics

Traditional analysis methods are susceptible to interference caused by the complexity of sample matrices, and detector surface fouling arising from nonspecific adsorption of microorganisms (in biological samples) which leads in particular to a gradual loss of sensitivity. Imprinted materials can be used to effectively reduce interference originating in the matrices. However, the poor reproducibility and multicomponent quantification of trace antibiotics represent significant challenges to the detection process. Meanwhile, the high biological risk presented by bacterial antibiotic immunity and the persistence of antibiotics in foodstuffs, especially meat, both caused by the overuse of sulfonamide antibiotics, remain urgent issues. Here, we present the first example of a method for the accurate quantification of trace sulfa antibiotics (SAs) based on multi-template imprinted polymers (MMIPs). Levels of multiple SAs have been simultaneously successfully quantified by applying MMIP extraction coupled with UPLC-MS/MS analysis. This method shows excellent linearity of detection in the range of 0.1-500 μg L^-1, and ultrasensitivity with low limits of detection of 0.03 μg L^-1. The maximum SA residue recovered from sample tissues by using MMIPs was 5.48 μg g^-1. MMIP-coupled UPLC-MS/MS quantification of SAs is an accurate and repeatable method for the monitoring of SA accumulation in mouse tissue samples. It also provides an effective strategy for the tracking and quantification of drugs in other biological samples.

Prioritizing pharmaceuticals based on environmental risks in the aquatic environment in China

In last two decades, the number of detected activated pharmaceutical ingredients (APIs) in the natural environment worldwide has increased due to their widespread use in daily life. However, given the large number of APIs that are currently in use (approximate 850 are on the market in China), it is impractical to investigate the occurrence, ecotoxicological effects, and perform environmental risk assessment for all drugs. Therefore, it is crucial to rank and prioritize APIs in the environment to identify the compounds of high concern. In China, since information on API usage is not available, an attempt was made to use the number of products per API (the number of pharmaceutical commodities that contain a particular API) on the market multiplied by its daily dose (average daily dose of medication for adults used for the primary therapeutic purpose) to replace the usage in the exposure modeling. Coupled with the hazard assessment, including acute and chronic toxicity of aquatic ecological effects and potential effects related to the therapeutic mode of action, risk scores were estimated and used for ranking. Application of the approach was illustrated for 259 APIs with product number no less than 4. A list of 20 APIs was finally identified as a potential priority, including drugs of cardiovascular, nervous system, respiratory system, musculoskeletal system and antibiotics. In the future, this approach could be applied to prioritize APIs in other countries/regions where information on API usage are limited or non-existent.

Multi-phase distribution, spatiotemporal variation and risk assessment of antibiotics in a typical urban-rural watershed

The widespread consumption and continuous discharge of antibiotics have threatened the ecological health of urban-rural watershed. In this study, multi-phase distribution, spatiotemporal variation and ecological risk of 18 antibiotics in rivers and lakes from Suzhou City were investigated based on urban-rural gradient. The total antibiotic concentration in surface water, suspended particulate matter (SPM) and sediments was 39.28-2578 ng/L, 6.16-171.09 ng/L and 12.67-2249 ng/g, respectively. High detection frequency (>76%) and concentration of antibiotics in multi-phase suggested universal pollution. Quinolones (QNs) and tetracycline (TCs) were the dominant antibiotics detected. The partitioning coefficient (K_P) value of SPM-water was 1.43-29.93 times larger than sediment-water, indicating that SPM can greatly affect the fate and distribution of antibiotics. Significant positive correlations between antibiotics and environmental parameters (e.g. TOC, TP and TN) revealed combined contamination and similar pollution sources. Antibiotic pollution exhibited evident spatiotemporal variation. For spatial variation, urban area showed more serious antibiotic pollution and greater ecological risk than rural and suburb areas, especially for sediments. Besides, antibiotic level and risk in rivers were higher than lakes. For seasonal variation, in case of surface water, rural area exhibited higher content in winter, while greater content was detected in autumn and spring in urban and suburb areas, respectively. The highest antibiotic content in SPM and sediments was all measured in winter owing to weak degradation ability. Ecological risk assessment based on risk quotients (RQs) indicated that norfloxacin (NFX), ciprofloxacin (CFX) and anhydroerythromycin (ETM-H₂O) in surface water presented medium to high risk throughout the entire year, while sulfadiazine (SDZ) and enrofloxacin (EFX) in sediments showed higher accumulation potential. Thus, these five antibiotics were selected as the priority antibiotics for pollution control. In short, this study improves the understanding of antibiotic fates in the urban-rural watershed and provides scientific basis for the authorities to regulate antibiotic pollution.

Involvement of oxidative stress in the sensitivity of two algal species exposed to roxithromycin

Algal species Raphidocelis subcapitata and Chlorella vulgaris are commonly used to test the chemicals with an antibacterial mode of action during marketing authorization process. However, significant differences in the sensitivity toward antibiotic exposure have been reported. The selection of an inappropriate test species would thus underestimate the environmental hazard of target chemicals and pose a potential threat to the ecosystem. Since oxidative stress is a crucial factor determining the inhibition of algal growth, an investigation on oxidative stress and antioxidant defense mechanisms in these two species was performed to explore its roles in species sensitivity. Here, roxithromycin (ROX), a macrolide antibiotic extensively used to treat respiratory, urinary and soft tissue infections, was used for testing. After 7 days exposure to ROX at the low (0.01 mg L^-1) and high (0.09 mg L^-1) concentrations, R. subcapitata was inhibited while the growth of C. vulgaris was stimulated. We investigated the roles of oxidative stress in algae by measuring the oxidative stress biomarkers (MDA), non-enzymatic antioxidants (GSH), and antioxidant enzymes (SOD, CAT, GP, GST). The results suggested that when the growth of algae is inhibited, MDA content as well as activities of oxidative stress enzymes would increase, and thus, activating the antioxidant system. On the contrary, it was inferred that when the growth is stimulated, MDA content and oxidative stress enzymes activities would decrease.

Comprehensive insights into the occurrence, distribution, risk assessment and indicator screening of antibiotics in a large drinking reservoir system

Drinking water reservoir is threatened globally due to anthropogenic contamination and thus in need of more attention. Here, we comprehensively investigated the occurrence, distribution and risk assessment of representative antibiotics in a large drinking water reservoir (Fengshuba Reservoir, China). The total concentrations of antibiotics in the water phase, porewater phase, sediment phase and soil phase (drawdown area) were in the ranges of 195-569 ng/L, 47.1-333 ng/L, 114-272 μg/kg and 2.84-77.2 μg/kg, respectively. The dominant antibiotic was CIP in both the water and porewater phases, while it was OTC in the sediment phase. For the water phase, seasonal factor consisting hydrologic condition and pattern of antibiotic use could influence the occurrence level and environmental fate of antibiotics. In contrast, exogenous particles derived from the soils that had used manures during the spring planting season coupled with heavy rainfall was responsible for the occurrence level and composition of antibiotics in the sediment phase. Moreover, Chl-α, NO₃^-, TP and EC were the most dominant factor influencing the antibiotic distributions in the water phase, porewater phase, sediment phase and soil phase, respectively. Pseudo-partitioning coefficients indicated that PENV and PENG might accumulate more easily into the sediments from the aqueous phase compared with other antibiotics. Risk assessments suggested that TC might pose high risks to the aquatic ecosystem, but the antibiotics presented no risk to the health of consumers. Generally, TC could be used as a promising indicator for evaluating the occurrence and potential risk of antibiotics in Fengshuba Reservoir.

A Novel Reduced Graphene Oxide-Attapulgite (RGO-ATP) Supported Fe2O3 Catalyst for Heterogeneous Fenton-like Oxidation of Ciprofloxacin: Degradation Mechanism and Pathway

Ciprofloxacin, a third-generation fluoroquinolones (FQs) antibiotic, is observed to increasingly pollute the environment. In this study, a three-dimensional reduced graphene oxide-attapulgite-based catalyst Fe2O3/RGO-ATP was prepared and used to analyze the degradation of ciprofloxacin in a heterogeneous Fenton reaction. The heterogeneous catalyst Fe2O3/RGO-ATP was prepared by a one-step hydrothermal method, and the samples were characterized using BET(Brunauer-Emmett-Teller) surface area, Raman spectroscopy, X-ray diffraction (XRD), Fourier infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The effect of reaction time, temperature, pH, initial concentration, H2O2 dosage and reuse time on the degradation of ciprofloxacin by the catalyst Fe2O3/RGO-ATP was investigated. The optimum conditions of degradation of ciprofloxacin are observed to be 60 °C, pH 5, H2O2 concentration of 2.9724 mmol/L, and initial ciprofloxacin concentration of 50 mg/L. The catalyst could be reused several times with a decline in catalytic capacity. Fourier-transform ion cyclotron resonance mass spectrometer (FT) was also employed to study the degradation products of ciprofloxacin in the aqueous solution. The results show that the heterogeneous catalyst Fe2O3/RGO-ATP possessed an excellent ability for the catalytic degradation of ciprofloxacin. Direct hydroxyl oxidation is noted to be the main pathway of degradation of ciprofloxacin, and no defluorination reaction is observed during the degradation process.

Biological Activity-Based Prioritization of Pharmaceuticals in Wastewater for Environmental Monitoring: G Protein-Coupled Receptor Inhibitors

Pharmaceuticals raise concerns for aquatic species owing to their biological activities. It is estimated that nearly 40% of marketed pharmaceuticals target G protein-coupled receptors (GPCRs). Using an in vitro transforming growth factor-α (TGFα) shedding assay, we previously detected antagonistic activities of GPCR-acting pharmaceuticals against angiotensin (AT1), dopamine (D2), acetylcholine (M1), adrenergic family members (β1), and histamine (H1) receptors at up to μg-antagonist-equivalent quantities/L in wastewater in England and Japan. However, which pharmaceuticals were responsible for biological activities in wastewater remained unclear. Here, we used (1) the consumption of GPCR-acting pharmaceuticals, particularly antagonists, as calculated from prescriptions, (2) their urinary excretion, and (3) their potency measured by the TGFα shedding assay to prioritize them for analysis in wastewater in England and Japan. We calculated predicted activities of 48 GPCR-acting pharmaceuticals in influents in England and Japan and identified which were mainly responsible for antagonistic activities in wastewater against each GPCR. Mixtures of pharmaceuticals tested in this study were confirmed to behave additively. The combination of consumption and potency is useful in prioritizing pharmaceuticals for environmental monitoring and toxicity testing.

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.

Silver nanoparticle probe for colorimetric detection of aminoglycoside antibiotics: picomolar-level sensitivity toward streptomycin in water, serum, and milk samples

BACKGROUND

The low cost of aminoglycoside (AMG) antibiotics facilitates their excessive use in animal husbandry and the agriculture sector. This scenario has led to the occurrence of residues in the food chain. After several years of AMG use in antibacterial therapy, resistance to streptomycin has begun to appear. Most of the detection methods developed for AMG antibiotics lacks specificity. A broad target specific nanoprobe would be ideal for detecting the entire class of AMGs. A rapid and sensitive method for the detection of AMGs is urgently needed.

RESULTS

Gallic acid-coated silver nanoparticles (AgNPs) were demonstrated as a nanoprobe for the colorimetric detection of AMGs (yellow to orange / red). A linear dynamic range of 50-650 pmol L^-1 was achieved readily by ratiometric spectrophotometry (A₅₆₀ /A₄₀₀ ) with a limit of detection (LOD) as low as 36 pmol L^-1 . The amine-groups of the AMGs function as molecular linkers, so that electrostatic coupling interactions between neighboring particles drive the formation of AgNP aggregates. The assay can also be applied for the determination of streptomycin residues in serum and milk samples.

CONCLUSION

This study revealed the potential of an AgNP probe for the rapid and cost-effective detection of low-molecular-weight target analytes, such as the AMGs. A ligand-induced aggregation of AgNPs coated with gallic acid was reported to be a rapid and sensitive assay for AMGs. Analysis of streptomycin was demonstrated with excellent picomolar-level sensitivity. Thus, the validated method can find practical applications in the ultrasensitive detection of AMGs in complex and diagnostic settings. © 2019 Society of Chemical Industry.

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.

Responses of seeds of typical Brassica crops to tetracycline stress: Sensitivity difference and source analysis

Antibiotics can induce adverse effects on plants. Brassica crop seeds, for their advantages, are used widely in seed germination test to investigate phytotoxicity of substances. However, their performances on evaluating antibiotics remain to be studied to select sensitive species for control of potential risks. In this work, common species of Chinese cabbage (Brassica rapa L.), edible rape (Brassica napus L.), and cabbage (Brassica oleracea L.) with three cultivars each were selected to compare and analyze the sensitivity difference of their seeds to tetracycline (TC) stress. Results showed that the ratio of axis to cotyledon (RAC) by fresh weight was an alternative endpoint besides radicle length (RL) in the test. The species sensitivity distribution (SSD) based on the effective concentrations causing x% inhibition (EC_x) in RL of seeds exposed to TC was applied to compare the sensitivity of seeds and estimate the hazardous concentration for x% species (HC_x). From the species-dependent sensitivity and the sensitivity difference of cultivars in the same species of seeds to TC, the performance of Chinese cabbage was the best in the study. The sensitivity of seeds to TC could be evaluated by EC₂₀ related to seed physical traits and germination indices, while the extent of seeds affected by TC could be evaluated by EC₅₀ related to the composition of seed storage reserves. We recommended that it was a new idea to analyze responses of different seeds to TC at large scale according to seed innate characteristics.

Effects of sunlight, microbial activity, and temperature on the declines of antibiotic lincomycin in freshwater and saline aquaculture pond waters and sediments

The residues of lincomycin (LIN), an antibiotic administered to aquatic animals, are often detected in aquatic environments. This study investigated effects of three environmental factors, sunlight, microbial activity, and temperature, on declines of spiked LIN in waters and sediment slurry samples collected from freshwater tilapia (Oreochromis mossambicus) and marine shrimp (Litopenaeus vannamei) culture ponds. The results showed that sunlight, temperature, and microbial activity all accelerated LIN transformation in the water and slurry samples. In matrixes of all water and slurry samples, LIN transformation was significantly faster under light conditions [half-life (t_1/2) = 24-53 days] than under dark conditions (t_1/2 = 154-2897 days). Microbial activity also accelerated LIN transformation; the t_1/2 of LIN was shorter after nonsterile treatment (t_1/2 = 12-809 days) than after sterile treatment (t_1/2 = 154-2897 days). Moreover, LIN transformation was faster at 28 °C (t_1/2 = 18-38 days) than at 20 and 12 °C (t_1/2 = 34 and 462 days, respectively) in both slurry samples. The results revealed that LIN transformation in aquaculture pond water and sediment was either slow or stagnant. Sunlight, microbial activity, and temperature can accelerate LIN transformation to reduce LIN residue levels.

DOM as an indicator of occurrence and risks of antibiotics in a city-river-reservoir system with multiple pollution sources

Multiple sources contribute to the presence of antibiotic residues in water environments, and the environmental risks caused by antibiotics were paid more and more attention. This work aims to establish a relationship between optical properties of dissolved organic matter (DOM) and sources and risks of antibiotics. Occurrence of antibiotics and DOM in a city-river-reservoir freshwater system containing distinct antibiotic sources was investigated during three seasons using LC-MS and fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC), respectively. The results showed that antibiotics and DOM in the water had trends of increasing levels from the upstream to the midstream in the system. Five classes of antibiotics had statistically significant correlations with the humic-like component (C3) in the water (Pearson, p < 0.05). Especially, norfloxacin (NFX), which was dominant in the aquaculture source, significantly increased the fluorescence of C3 according to the fluorescence titration (R² = 0.86, p < 0.01). Furthermore, fluorescence signature in the aquaculture pond posed broad humic acid-like peaks with relatively higher abundances compared to other areas. These results suggested that C3 could be recognized as an indicator of NFX from aquaculture sources. Meanwhile, C3 can largely account for ecological risks of tetracyclines according to the results of redundancy analysis. This work highlights the roles of EEM-PARAFAC on tracing the source of antibiotics and the correlations between environmental risks of antibiotics and DOM in the aquatic environment.

Concentration and reduction of antibiotic residues in selected wastewater treatment plants and receiving waterbodies in Durban, South Africa

In the province of KwaZulu-Natal, South Africa the incidence of resistant tuberculosis, upper respiratory tract diseases as well as diarrhoeal and parasitic infections is high. Treatment of these diseases with antibiotics is partly reflected by the excretion of the respective antibiotics and their subsequent occurrence in wastewater. Their quantitative reduction in wastewater treatment reflects their potential environmental as well as human impact, the latter due to the use of the recipient water for domestic purposes and for irrigation. Information of the occurrence and reduction of different classes of antibiotics in wastewater treatment is sparse, especially the particle bound fraction of these. Due to this, analyses of aqueous and particle bound antibiotics in untreated wastewater of four selected wastewater treatment plants (WWTPs) and their receiving water bodies was carried out in Durban, South Africa. The treatment step especially considered was the biological one, represented by activated sludge and trickling filters. The treatment further included secondary clarifiers and final chlorine disinfection. Composite samples were collected during the period February 2017 to May 2017 and analysed with online solid phase extraction - high performance liquid chromatography mass spectrometry (SPE-HPLC-MS). For the 13 assessed antibiotics, the limit of detection (LOD) and the limit of quantification (LOQ) ranged from 0.07 to 0.33 ng L^-1 and 0.23 to 1.09 ng L^-1 respectively, while the total percentage recovery was in the range of 51 to 111%. The percentage of individual antibiotics bound to the particulate fraction normally lost by sample (influent) filtration, if not analysed in parallel, was in the range of 2.6%-97.3% (n = 32). In this fraction (sludge from centrifuge sample), the concentration of bound antibiotics of all the target antibiotics were detected in the influent of all WWTP in concentration ranges between 1.3 ng L^-1 (Azithromycin; AZI) to 81,748 ng L^-1 (Ciprofloxacin; CIP). The antibiotics with the highest median concentrations in receiving water bodies of the respective WWTP were; Sulfamethoxazole; SUL (239 ng L^-1) WWTP "K", Ciprofloxacin; CIP (708 ng L^-1) WWTP "S" and Albendazole; ALB (325 ng L^-1 and 683 ng L^-1) WWTP "P" and "I" respectively. The overall percentage removal efficiency for the four WWTPs ranged from 21% to 100%. The biological treatment steps, activated sludge and trickling filters, were effective in removing antibiotics especially with the trickling filter and the impact of the sedimentation stage after activated sludge treatment.

Presence and environmental risk assessment of selected antibiotics in coastal water adjacent to mariculture areas in the Bohai Sea

The presence and concentrations of 25 antibiotics in Dalian coastal water of the Bohai Sea were investigated using solid-phase extraction coupled with high-performance liquid chromatography tandem mass spectrometry. Results showed that antibiotics were widely detected in this region with total concentration ranging from 22.6 to 2402.4 ng/L. Enrofloxacin and trimethoprim were 100% detected followed by sulfamethoxazole with a detection rate of 90.9%. No significant correlations were found between antibiotics concentrations and sample parameters such as dissolved organic carbon, salinity, and distance from the coast, suggesting that concentrations and distributions of the antibiotics in this area were source-dependent. Antibiotic concentration in the sample from an offshore cage-culture area was the highest. Based on composition profiles, mariculture was supposed to be an important source of antibiotics. According to the assessment, individual antibiotic posed low to moderate risk, while the antibiotic mixture presented high risk. Enrofloxacin, clarithromycin and sulfamethoxazole, the top three contributors to the mixture risk quotients for each site, need priority control in this area. Besides, levels of enrofloxacin were high enough to exert a selective pressure on bacteria that may lead to an increase in the prevalence of resistance.

Water depollution using metal-organic frameworks-catalyzed advanced oxidation processes: A review

This paper presents a review on the environmental applications of metal-organic frameworks (MOFs), which are inorganic-organic hybrid highly porous crystalline materials, prepared from metal ion/clusters and multidentate organic ligands. The emphases are made on the enhancement of the performance of advanced oxidation processes (AOPs) (photocatalysis, Fenton reaction methods, and sulfate radical (SO₄^-)-mediated oxidations) using MOFs materials. MOFs act as adsorption and light absorbers, leading to superior performance of photocatalytic processes. More recent examples of photocatalytic degradation of dyes are presented. Additionally, it is commonly shown that Fe-based MOFs exhibited excellent catalytic performance on the Fenton-based and SO₄^•--mediated oxidations of organic pollutants (e.g., dyes, phenol and pharmaceuticals). The significantly enhanced generation of reactive species such as OH and/or SO₄^- by both homogeneous and heterogeneous catalysis was proposed as the possible mechanism for water depollution. Based on the existing literature, the challenge and future perspectives in MOF-based AOPs are addressed.

Combined effects of sulfamethazine and sulfamethoxazole on a freshwater microalga, Scenedesmus obliquus: toxicity, biodegradation, and metabolic fate

This study investigated the environmental effects of two common emerging contaminants, sulfamethazine (SMZ) and sulfamethoxazole (SMX), and their mixture using a green microalga, Scenedesmus obliquus. The calculated EC₅₀ values of SMZ, SMX, and their mixture (11:1 wt/wt) after 96 h were 1.23, 0.12, and 0.89 mg L^-1, respectively. The toxicity of the mixture could be better predicted using a concentration addition model than an independent action model. The risk quotients of SMZ, SMX, and their mixture were >1 during the experiment, indicating their high potential risks on aquatic microorganisms. Despite their toxicity, S. obliquus exhibited 17.3% and 29.3% removal of 0.1 mg L^-1 and 0.2 mg L^-1 after 11 days of cultivation. The changes of SMZ and SMX removal were observed when combined, which showed a significantly improved removal of SMZ (up to 3.4 folds) with addition of SMX (0.2 mg L^-1). The metabolic pathways of SMZ and SMX were proposed according to mass spectroscopic analysis, which showed six metabolites of SMX and seven intermediates of SMZ, formed as a result of ring cleavage, hydroxylation, methylation, nitrosation, and deamination.

Benthic Diatom Communities in an Alpine River Impacted by Waste Water Treatment Effluents as Revealed Using DNA Metabarcoding

Freshwater ecosystems are continuously affected by anthropogenic pressure. One of the main sources of contamination comes from wastewater treatment plant (WWTP) effluents that contain wide range of micro- and macropollutants. Chemical composition, toxicity levels and impact of treated effluents (TEs) on the recipient aquatic ecosystems may strongly differ depending on the wastewater origin. Compared to urban TEs, hospital ones may contain more active pharmaceutical substances. Benthic diatoms are relevant ecological indicators because of their high species and ecological diversity and rapid response to human pressure. They are routinely used for water quality monitoring. However, there is a knowledge gap on diatom communities’ development and behavior in treated wastewater in relation to prevailing micro- and macropollutants. In this study, we aim to (1) investigate the response of diatom communities to urban and hospital TEs, and (2) evaluate TEs effect on communities in the recipient river. Environmental biofilms were colonized in TEs and the recipient river up- and downstream from the WWTP output to study benthic diatoms using DNA metabarcoding combined with high-throughput sequencing (HTS). In parallel, concentrations of nutrients, pharmaceuticals and seasonal conditions were recorded. Diatom metabarcoding showed that benthic communities differed strongly in their diversity and structure depending on the habitat. TE sites were generally dominated by few genera with polysaprobic preferences belonging to the motile guild, while river sites favored diverse communities from oligotrophic and oligosaprobic groups. Seasonal changes were visible to lower extent. To categorize parameters important for diatom changes we performed redundancy analysis which suggested that communities within TE sites were associated to higher concentrations of beta-blockers and non-steroidal anti-inflammatory drugs in urban effluents vs. antibiotics and orthophosphate in hospital effluents. Furthermore, indicator species analysis showed that 27% of OTUs detected in river downstream communities were indicator for urban or hospital TE sites and were absent in the river upstream. Finally, biological diatom index (BDI) calculated to evaluate the ecological status of the recipient river suggested water quality decrease linked to the release of TEs. Thus, in-depth assessment of diatom community composition using DNA metabarcoding is proposed as a promising technique to highlight the disturbing effect of pollutants in Alpine rivers.

Assessment of Soil to Mitigate Antibiotics in the Environment Due to Release of Wastewater Treatment Plant Effluent

With low levels of human antibiotics in the environment due to release of wastewater treatment plant (WWTP) effluent, concern is rising about impacts on human health and antibiotic resistance development. Furthermore, WWTP effluent may be released into waterways used as drinking water sources. The aim of this study was to analyze three antibiotics important to human health (sulfamethoxazole, ofloxacin, and trimethoprim) in soil and groundwater at a long-term wastewater reuse system that spray irrigates effluent. Soil samples were collected (i) at a site that had not received irrigation for 7 mo (approximate background concentrations), and then at the same site after (ii) one irrigation event and (iii) 10 wk of irrigation. Water samples were collected three times per year to capture seasonal variability. Sulfamethoxazole was typically at the highest concentrations in effluent (22 ± 3.7 μg L) with ofloxacin and trimethoprim at 2.2 ± 0.6 and 1.0 ± 0.02 μg L, respectively. In the soil, ofloxacin had the highest background concentrations (650 ± 204 ng kg), whereas concentrations of sulfamethoxazole were highest after continuous effluent irrigation (730 ± 360 ng kg). Trimethoprim was only quantified in soil after 10 wk of effluent irrigation (190 ± 71 ng kg). Groundwater concentrations were typically <25 ng L with high concentrations of 660 ± 20 and 67 ± 7.0 ng L for sulfamethoxazole and ofloxacin, respectively. Given that antibiotics interacted with the soil profile and groundwater concentrations were frequently about 1000-fold lower than effluent, soil may be an adequate tertiary treatment for WWTP effluent leading to improved water quality and protection of human health.

Occurrence, fate and mass loadings of antibiotics in two swine wastewater treatment systems

Antibiotics are widely applied in livestock industry to prevent or treat animal diseases. However, those antibiotics are poorly metabolized in livestock animals, most of them being excreted via feces or urine. Hence we need to understand the removal of antibiotics in swine farm wastewater treatment systems. This study investigated occurrence and fate of various antibiotics in two full-scale swine farm wastewater treatment systems (Farm A: anaerobic digester-A²/O-lagoon; Farm B: upflow anaerobic sludge blanket (UASB)-(A/O)²-lagoon). The results showed the presence of 25 antibiotics out of 40 target antibiotics in the wastewater and sludge samples from the two farms. In Farm A, sulfamonomethoxine, sulfachlorpyridazine, oxytetracycline and lincomycin were predominant in the influent with concentrations up to 166 ± 3.64 μg/L, while in the dewatered sludge chlortetracycline, oxytetracycline, tetracycline and norfloxacin were the predominant target compounds with concentrations up to 29.2 ± 3.74 μg/g. In Farm B, high concentrations (up to 3630 ± 1040 μg/L) of sulfachlorpyridazine, sulfamonomethoxine and lincomycin were detected in the influent, and the predominant target antibiotics detected in the dewater sludge were similar to those in Farm A, with concentrations up to 28.6 ± 0.592 μg/g. The aqueous removal rates for the total antibiotics were >99.0% in the wastewater treatment plants of both farms. Among a series of treatment units, the anaerobic digester in Farm A and UASB in Farm B made a significant contribution to the elimination of the target antibiotics from the animal wastewater. The daily mass loadings of total antibiotics in the manure, influent, dewatered sludge and effluent were 17.1, 28.0, 2.53, and 0.0730 g/d for Farm A and 24.5, 354, 3.17, and 0.293 g/d for Farm B. The full-scale swine wastewater treatment facilities could effectively remove antibiotics from swine wastewater, but the dewatered sludge needs to be further treated before disposal on land.

Antibiotics in surface water and sediments from Hanjiang River, Central China: Occurrence, behavior and risk assessment

Thirteen antibiotics including sulfonamides (SAs), tetracyclines (TETs) and fluoroquinolones (FQs) were measured in Hanjiang River (HR) during two periods. The total concentrations of 13 antibiotics in surface water and sediments ranged from 3.1 to 109 ng/l and from 10 to 45 ng/g dry weight, respectively. SAs were dominant in water while the concentrations of TETs were the highest in sediments in two seasons. For their spatial distribution, total concentrations of 13 antibiotics in both matrices were significantly higher in the lower section of HR (p < 0.02, F > 5.15) due to wastewater release, agricultural activities and water transfer project. Obvious seasonal variations of sulfadiazine, sulfameter, trimethoprim and oxytetracycline in water were observed (p < 0.05, F > 4.62). Phase partition of antibiotics between water and sediments suggested a greater affinity of TETs and FQs to sediments. In addition, significantly positive relationships were found between SAs (sulfameter, sulfamethoxazole and trimethoprim) and sediment TOC (p < 0.05). Risk assessment indicated that the hazard quotients of antibiotics were higher in the sediment than those in the water. Moreover, antibiotic mixtures posed higher ecological risks to aquatic organisms.

Sustained antibacterial activity of berberine hydrochloride loaded supramolecular organoclay networks with hydrogen-bonding junctions

The environmental risk from antibiotics is an issue of increasing concern. So, carboxymethyl β-cyclodextrin-functionalized montmorillonite nanosheets were for the first time successfully synthesized through a cheap, environmentally friendly and scalable approach and confirmed by FTIR, XRD and TGA. FE-SEM investigation showed that the resulting functional material could be further self-assembled into dense supramolecular organoclay networks (D-networks). The antibacterial properties of the D-networks loaded with natural berberine hydrochloride (BBH) were investigated toward E. coli and S. aureus by using colony growth on agar plates, bacterial growth curves based on optical densities, and confocal and fluorescence microscopy. Our studies demonstrated that the BBH loaded D-network antibacterial activity was concentration dependent and significantly exceeded that of free BBH. FE-SEM observation confirmed that E. coli and S. aureus can directly contact the D-networks and confocal and fluorescence microscopy showed that free BBH was only very poorly internalized, while the BBH released from the BBH-loaded D-network could be internalized efficiently into bacterial cells, resulting in an increment of the intracellular BBH level compared with the free BBH group. Time-dependent antibacterial activity was observed and it was found that the BBH-loaded D-network dispersion at the BBH dosage of 600 μg mL^-1 almost completely suppressed the growth of E. coli, leading to a viability loss of up to 98.45 ± 1.22%, while the BBH-loaded D-network dispersion at the BBH concentration of 250 μg mL^-1 exhibited a growth inhibition of 97.81 ± 0.83% toward S. aureus over three days. Our results suggest that supramolecular organoclay networks, in the future, may function as promising antibacterial drug carrier systems to promote BBH delivery in E. coli and S. aureus, which can reduce the environmental risk of antibiotics.

Multiclass screening of >200 pharmaceutical and other residues in aquatic foods by ultrahigh-performance liquid chromatography-quadrupole-Orbitrap mass spectrometry

A quick screening method of more than 200 pharmaceutical and other residues in aquatic foods based on ultrahigh-performance liquid chromatography-quadrupole-Orbitrap mass spectrometry (UHPLC-Q/Orbitrap MS) was established. In this method, after the addition of 200 μL of 1 M EDTA-Na₂, 2 g of each sample homogenate was extracted successively with 10 mL of acetonitrile and 10 mL of ethyl acetate. The extracts were combined, dried under nitrogen flow, and redissolved in 0.1% formic acid in acetonitrile/water (4:6, v/v) for analysis. The prepared samples were analyzed by UHPLC- Q/Orbitrap MS system in Full MS/ddMS² (full-scan data-dependent MS/MS) mode. Compound identification was performed through comparison of the sample data with the database for standard chemicals, including the retention time, precursor ion, product ions, and isotope pattern for all 206 compounds. Five different aquatic food matrices (carp, shrimp, crab, eel, and mussel) spiked with the analytes at 1, 10, and 50 ng/g were evaluated to assess recoveries, precision, matrix effects, stability, and detection limits using the method. UHPLC analyses required 25 min, and 178-200 analytes met identification criteria at 50 ng/g depending on the matrix. Furthermore, practical application of this method for real samples displayed strong screening capability. Graphical abstract A quick screening method of >200 pharmaceutical and other residues in aquatic foods based on ultrahighperformance liquid chromatography-quadrupole-Orbitrap mass spectrometer was established. Fivedifferent aquatic food matrices, including carp, shrimp, crab, eel and mussel, were studied to evaluatescreen limit at 1, 10 and 50 μg·kg-1 level. Results suggest the high reliability, high time-efficiency and goodsimplicity of the method.

Occurrence and indicators of pharmaceuticals in Chinese streams: A nationwide study

Pharmaceutically active compounds (PhACs) are excreted by humans and animals and released into the aquatic environment through wastewater, which can have potential negative impacts on ecological systems. To conduct a nationwide investigation of the occurrence of PhACs in water resources in China, an analytical procedure based on solid-phase extraction (SPE) and LC-MS/MS was used to measure 45 PhACs in surface water samples from a network of 29 rivers across 31 provinces in China in 2014 and 2015. PhACs were prevalent in all sampled streams. The concentrations of commonly detected PhACs were comparable to those detected in other countries. High total concentrations (mean > 1 μg L^-1) of all tested PhACs were primarily detected in areas under extreme water stress, specifically northern and eastern coastal areas. Source apportionment based on the profiles of the target compounds found that 54% of the PhACs in China originated from freshly discharged untreated sewage. Metformin (MET) and its biodegradation product, guanylurea (GUL), were used as a pair of indicators to predict PhAC contamination levels and differentiate between biotreated and unbiotreated wastewater. High MET/GUL can be used to indicate untreated wastewater, whereas low MET/GUL values are a strong indicator of treated wastewater. Furthermore, wastewater biotreatment ratios were calculated. We estimated that the biotreatment ratios of most of the provinces in China were less than 50%. We conclude that more attention should be paid to untreated sewage water, especially water in rural areas rather than the existing concentration on urban sewage treatment-oriented management.

Electrochemical synthesis of ferrate(VI) using sponge iron anode and oxidative transformations of antibiotic and pesticide

Passivation of anode is a main challenge in the electrochemical synthesis of ferrate(VI) (Fe^VIO₄^2-, Fe(VI)). A series of electrochemical approaches were employed including polarization curve, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) to analyze the physicochemical processes involved in electrochemical synthesis of Fe(VI) using sponge iron and cast iron anodes. The results demonstrate that the sponge iron anode achieved higher yield of Fe(VI) compared to grey cast iron anode. The optimum condition to generate Fe(VI) using sponge iron was 35-50°C and 30mA/cm². Significantly, the sponge iron anode could generate Fe(VI) for a long duration (>10h) under these conditions; possibly suitable for large scale synthesis of Fe(VI). The prepared Fe(VI) solution was used to treat antibiotic (sulfamethoxazole (SMX)) and pesticide (atrazine (ATZ)) in water. At a molar ratio of Fe(VI) to SMX as 20:1 in the pH range from 5.0 to 9.0, almost complete oxidative transformation of SMX could be obtained. Comparatively, oxidative transformation of ATZ was incomplete (∼70%) even when [Fe(VI)]:[ATZ]=87 at pH 5.0-9.0. Fluorescence spectra and cytotoxicity studies suggest that the oxidative transformation products of both SMX and ATZ possess lower toxicity than the parent antibiotic and pesticide, respectively.

Metal-mediated oxidation of fluoroquinolone antibiotics in water: A review on kinetics, transformation products, and toxicity assessment

Fluoroquinolones (FQs) are among the most potent antimicrobial agents, which have seen their increasing use as human and veterinary medicines to control bacterial infections. FQs have been extensively found in surface water and municipal wastewaters, which has raised great concerns due to their negative impacts to humans and ecological health. It is of utmost importance that FQs are treated before their release into the environment. This paper reviews oxidative removal of FQs using reactive oxygen (O₃ and OH), sulfate radicals (SO₄^-), and high-valent transition metal (Mn^VII and Fe^VI) species. The role of metals in enhancing the performance of reactive oxygen and sulfur species is presented. The catalysts can significantly enhance the production of OH and/or SO₄^- radicals. At neutral pH, the second-order rate constants (k, M^-1s^-1) of the reactions between FQs and oxidants follow the order as k(OH)>k(O₃)>k(Fe^VI)>k(Mn^VII). Moieties involved to transform target FQs to oxidized products and participation of the catalysts in the reaction pathways are discussed. Generally, the piperazinyl ring of FQs was found as the preferential attack site by each oxidant. Meanwhile, evaluation of aquatic ecotoxicity of the transformation products of FQs by these treatments is summarized.