Profile and behavior of antiviral drugs in aquatic environments of the Pearl River Delta, China

Ecological implications and drivers of emerging contaminants in Dongting Lake of Yangtze River Basin, China: A multi-substance risk analysis

Emerging contaminants (ECs) are increasingly recognized as a global threat to biodiversity and ecosystem health. However, the cumulative risks posed by ECs to aquatic organisms and ecosystems, as well as the influence of anthropogenic activities and natural factors on these risks, remain poorly understood. This study assessed the mixed risks of ECs in Dongting Lake, a Ramsar Convention-classified Typically Changing Wetland, to elucidate the major EC classes, key risk drivers, and magnitude of anthropogenic and natural impacts. Results revealed that ECs pose non-negligible acute (30% probability) and chronic (70% probability) mixed risks to aquatic organisms in the freshwater lake ecosystem, with imidacloprid identified as the primary pollutant stressor. Redundancy analysis (RDA) and structural equation modeling (SEM) indicated that cropland and precipitation were major drivers of EC contamination levels and ecological risk. Cropland was positively associated with EC concentrations, while precipitation exhibited a dilution effect. These findings provide critical insights into the ecological risk status and key risk drivers in a typical freshwater lake ecosystem, offering data-driven support for the control and management of ECs in China.

Assessing the impact of antiviral drugs commonly utilized during the COVID-19 pandemic on the embryonic development of Xenopus laevis

The antiviral drugs favipiravir and oseltamivir are widely used to treat viral infections, including coronavirus 2019 (COVID-19), and their levels are expected to increase in the aquatic environment. In this study, the potential toxic and teratogenic effects of these drugs were evaluated using the frog embryo teratogenesis assay Xenopus (FETAX). In addition, glutathione S-transferase (GST), glutathione reductase (GR), catalase, carboxylesterase (CaE), and acetylcholinesterase (AChE) enzyme activities and malondialdehyde levels were measured as biochemical markers in embryos and tadpoles for comparative assessment of the sublethal effects of the test compounds. Prior to embryo exposure, drug concentrations in the exposure medium were measured with high-performance liquid chromatography. The 96-h median lethal concentration (LC50) was 137.9 and 32.3 mg/L for favipiravir and oseltamivir, respectively. The teratogenic index for favipiravir was 4.67. Both favipiravir and oseltamivir inhibited GR, CaE, and AChE activities in embryos, while favipiravir increased the GST and CaE activities in tadpoles. In conclusion, favipiravir, for which teratogenicity data are available in mammalian test organisms and human teratogenicity is controversial, inhibited Xenopus laevis embryo development and was teratogenic. In addition, sublethal concentrations of both drugs altered the biochemical responses in embryos and tadpoles, with differences between the developmental stages.

Acyclovir eco-geno-toxicity in freshwater organisms

This study explores the eco-geno-toxic impact of Acyclovir (ACV), a widely used antiviral drug, on various freshwater organisms, given its increasing detection in surface waters. The research focused on non-target organisms, including the green alga Raphidocelis subcapitata, the rotifer Brachionus calyciflorus, the cladoceran crustacean Ceriodaphnia dubia, and the benthic ostracod Heterocypris incongruens, exposed to ACV to assess both acute and chronic toxicity. The results indicate that while acute toxicity occurs at environmentally not-relevant concentrations, a significant chronic toxicity for C. dubia (EC50 = 0.03 µg/L, NOEC = 0.02·10-2 µg/L), highlighted substantial environmental concern. Furthermore, DNA strand breaks and reactive oxygen species detected in C. dubia indicate significant increase at concentrations exceeding 200 µg/L. Regarding environmental risk, the authors identified chronic exposures to acyclovir causing inhibitory effects on reproduction in B. calyciflorus at hundreds of µg/L and hundredths of µg/L for C. dubia as environmentally relevant environmental concentrations. The study concludes by quantifying the toxic and genotoxic risks of ACV showing a chronic risk quotient higher than the critical value of 1and a genotoxic risk quotient reaching this threshold, highlighting the urgent need for a broader risk assessment of ACV for its significant implications for aquatic ecosystems.

Chlorination of antiviral drug ribavirin: Kinetics, nontargeted identification, and concomitant toxicity evolution

Residual antiviral drugs in wastewater may increase the risk of generating transformation products (TPs) during wastewater treatment. Therefore, chlorination behavior and toxicity evolution are essential to understand the secondary ecological risk associated with their TPs. Herein, chlorination kinetics, transformation pathways, and secondary risks of ribavirin (RBV), one of the most commonly used broad-spectrum antivirals, were investigated. The pH-dependent second-order rate constants k increased from 0.18 M-1·s-1 (pH 5.8) to 1.53 M-1·s-1 (pH 8.0) due to neutral RBV and ClO- as dominant species. 12 TPs were identified using high-resolution mass spectrometry in a nontargeted approach, of which 6 TPs were reported for the first time, and their chlorination pathways were elucidated. The luminescence inhibition rate of Vibrio fischeri exposed to chlorinated RBV solution was positively correlated with initial free active chlorine, probably due to the accumulation of toxic TPs. Quantitative structure-activity relationship prediction identified 7 TPs with elevated toxicity, concentrating on developmental toxicity and bioconcentration factors, which explained the increased toxicity of chlorinated RBV. Overall, this study highlights the urgent need to minimize the discharge of toxic chlorinated TPs into aquatic environments and contributes to environmental risk control in future pandemics and regions with high consumption of antivirals.

Ozonation products of purine derivatives, the basic structures of antiviral micropollutants

Purine and its nucleobases adenine and guanine are the basic structures of a large group of antiviral agents such as acyclovir and penciclovir. Hence, their ozonation is of interest with regard to wastewater treatment due to the formation of products that could affect the aquatic environment. In this study, the transformation products of the mentioned substances are investigated under different defined reaction conditions in order to gain insight into the ozonation characteristics of this compound class. Results show that examining related molecules significantly improves product screening by compiling known products and analogues leading to comprehensive candidate lists, for the purines with a total number of >120 candidates (including possible duplicates for several purines) of which 49 were detected for the derivatives studied. One product, cyanuric acid, which was previously postulated for adenine, was tentatively confirmed and quantified for the first time for the reaction of purine and adenine with ozone. In addition, two prioritisation approaches are presented to identify the major products that are either formed under specific reaction conditions or are potentially relevant for structurally related pollutants. First, principal component analysis allowed the prioritisation of the products formed according to reaction conditions. In the analysis of guanine and the two antivirals, this approach showed that at neutral and basic pH the 2-imino-5-oxoimidazoline products dominated while at acidic pH either analogues of 5-amino-2,4-imidazolidinedione or 2,4-diamino-1,3-oxazol-5-(2H)-one were abundant. A second approach prioritising common products in the ozonation of all three basic structures revealed the formation of two products that had not been reported before: C4H8O3 and C3H2N2O3, presumably oxalylurea. Both molecules or their analogues may also be formed from related micropollutants. Overall, examining basic structures and exemplary micropollutants in combination was shown to be a worthwhile approach to gain knowledge on the ozonation of a whole range of compounds.

Ecological risk assessment of the typical anti-epidemic drugs in the Pearl River Delta by tracing their source and residual characteristics

Since the outbreak of the COVID-19 pandemic, the anti-epidemic drugs have been used in extraordinary quantities with high intensity, and concerns have grown about their potential ecological risks due to their continued release and persistence in the receiving environments. A systematic investigation, covering the samples from hospital wastewater, effluent from wastewater treatment plants and receiving water bodies in the Pearl River Delta Region (PRDR), was carried out and aimed at tracing the sources and fate of 30 typical anti-epidemic in different water matrixes and evaluating their ecological risk. The results showed that these typical anti-epidemic drugs residues were detected in most of the sampling sites, with the highest concentration measured in hospital wastewater, whose concentrations were as high as ppb level, while the highest concentration of the surface water samples in tributaries was lower than ppb level. Anti-epidemic drugs contained in hospital wastewater and effluent from WWTPs were the main sources of drug residues in the surface water of this region. In the surface water of PRDR, although the detected concentration anti-epidemic drugs were basically in the range of 0-10 ng/L. The risk quotient of several anti-epidemic drugs, including Ciprofloxacin (CFX), Ofloxacin (OFX), Erythromycin (ETM), Clindamycin (CLI), and Sulfamethoxazole (SMX), was calculated to be a high value, which indicated that they might cause non-negligible ecological risk to the aquatic environment.

Effects of organic matter and alkalinity on the ozonation of antiviral purine derivatives as exemplary micropollutant motif

Ozonation of micropollutants strongly depends on the water matrix. Natural organic matter is known to highly affect the hydroxyl radical exposure due to radical promoting and inhibiting effects. Other important matrix components in ozonation are carbonate species which scavenge hydroxyl radicals. However, additional factors such as the formation of other radicals might also play a role but are generally not covered in research or considered in modelling of micropollutant degradation. Hence, the ozonation of purine derivatives, the basic structure of various antiviral micropollutants, in different artificial water matrices is investigated in this study with focus on the impact of natural organic matter and increasing alkalinity on the degradation and product formation. The degradation of purine and adenine is inhibited by bicarbonate in the water matrix due to the anion's scavenging of hydroxyl radicals. This effect is already observed for low bicarbonate concentrations of 0.3 mM. However, formed carbonate radicals contribute to the compounds' degradation and also affect the stability of transformation products. This effect gains in relevance with increasing alkalinity and needs consideration in evaluating ozonation of very hard waters. Three ozonation products are evaluated in detail, which are affected by the matrix due to impacts on ozone stability, hydroxyl radical yield and carbonate radical formation. One product of adenine with the mass 147 was reported for the first time and only occurs in presence of matrix components. Under typical water treatment conditions rough predictions of pollutants' degradation are possible by the Rct concept using ozone and hydroxyl radical exposures. However, other reactive species such as carbonate radicals are not considered leading to deviations between modelled and experimental data at extreme conditions such as industrial wastewater. A general correlation between the Rct and the fraction f of hydroxyl radicals scavenged by bicarbonate (ln(Rct) = - 5.9  ×  f - 16.3) calculated from the concentration of organic matter and alkalinity was observed for various water samples allowing the estimation of micropollutant degradation during ozone treatment at moderate conditions by simple organic and inorganic carbon measurements.

Recent Developments in Semiconductor-Based Photocatalytic Degradation of Antiviral Drug Pollutants

The prevalence of antiviral drugs (ATVs) has seen a substantial increase in response to the COVID-19 pandemic, leading to heightened concentrations of these pharmaceuticals in wastewater systems. The hydrophilic nature of ATVs has been identified as a significant factor contributing to the low degradation efficiency observed in wastewater treatment plants. This characteristic often necessitates the implementation of additional treatment steps to achieve the complete degradation of ATVs. Semiconductor-based photocatalysis has garnered considerable attention due to its promising potential in achieving efficient degradation rates and subsequent mineralization of pollutants, leveraging the inexhaustible energy of sunlight. However, in recent years, there have been few comprehensive reports that have thoroughly summarized and analyzed the application of photocatalysis for the removal of ATVs. This review commences by summarizing the types and occurrence of ATVs. Furthermore, it places a significant emphasis on delivering a comprehensive summary and analysis of the characteristics pertaining to the photocatalytic elimination of ATVs, utilizing semiconductor photocatalysts such as metal oxides, doped metal oxides, and heterojunctions. Ultimately, the review sheds light on the identified research gaps and key concerns, offering invaluable insights to steer future investigations in this field.

Ranking the risks of eighty pharmaceuticals in surface water of a megacity: A multilevel optimization strategy

Pharmaceuticals in freshwater posed ecological risks to aquatic ecosystem, however, most risk assessments of pharmaceuticals were conducted at screening level, which were limited by the availability of the toxicity data. In this study, risks of 80 pharmaceuticals including 35 antibiotics, 13 antiviral drugs, 13 illicit drugs, and 19 antidepressants in surface water of Beijing were assessed with a proposed multilevel environmental risk optimization strategy. Target pharmaceuticals were detected in surface water samples with the detection frequency from 1.7 % to 100 % and the total concentrations from 31.1 ng/L to 2708 ng/L. Antiviral drugs were the dominant pharmaceuticals. Preliminary screening-level risk assessment indicated that 20 pharmaceuticals posed low to high risks with risk quotient from 0.14 (chloroquine diphosphate) to 27.8 (clarithromycin). Thirteen pharmaceuticals were recognized with low to high risks by an optimized risk assessment method. Of them, the refined probabilistic risk assessment of joint probability curves coupling with a quantitative structure activity relationship-interspecies correlation estimation (QSAR-ICE) model was applied. Clarithromycin, erythromycin and ofloxacin were identified to pose low risks with maximum risk products (RP) of 1.23 %, 0.41 % and 0.35 %, respectively, while 10 pharmaceuticals posed de minimis risks. Structural equation modeling disclosed that human land use and climate conditions influenced the risks of pharmaceuticals by indirectly influencing the concentrations of pharmaceuticals. The results indicated that the multilevel strategy coupling with QSAR-ICE model was appropriate and effective for screening priority pollutants, and the strategy can be used to prioritize pharmaceuticals and other emerging contaminants in the aquatic environment.

Antimicrobial Transformation Products in the Aquatic Environment: Global Occurrence, Ecotoxicological Risks, and Potential of Antibiotic Resistance

The global spread of antimicrobial resistance (AMR) is concerning for the health of humans, animals, and the environment in a One Health perspective. Assessments of AMR and associated environmental hazards mostly focus on antimicrobial parent compounds, while largely overlooking their transformation products (TPs). This review lists antimicrobial TPs identified in surface water environments and examines their potential for AMR promotion, ecological risk, as well as human health and environmental hazards using in silico models. Our review also summarizes the key transformation compartments of TPs, related pathways for TPs reaching surface waters and methodologies for studying the fate of TPs. The 56 antimicrobial TPs covered by the review were prioritized via scoring and ranking of various risk and hazard parameters. Most data on occurrences to date have been reported in Europe, while little is known about antibiotic TPs in Africa, Central and South America, Asia, and Oceania. Occurrence data on antiviral TPs and other antibacterial TPs are even scarcer. We propose evaluation of structural similarity between parent compounds and TPs for TP risk assessment. We predicted a risk of AMR for 13 TPs, especially TPs of tetracyclines and macrolides. We estimated the ecotoxicological effect concentrations of TPs from the experimental effect data of the parent chemical for bacteria, algae and water fleas, scaled by potency differences predicted by quantitative structure-activity relationships (QSARs) for baseline toxicity and a scaling factor for structural similarity. Inclusion of TPs in mixtures with their parent increased the ecological risk quotient over the threshold of one for 7 of the 24 antimicrobials included in this analysis, while only one parent had a risk quotient above one. Thirteen TPs, from which 6 were macrolide TPs, posed a risk to at least one of the three tested species. There were 12/21 TPs identified that are likely to exhibit a similar or higher level of mutagenicity/carcinogenicity, respectively, than their parent compound, with tetracycline TPs often showing increased mutagenicity. Most TPs with increased carcinogenicity belonged to sulfonamides. Most of the TPs were predicted to be mobile but not bioaccumulative, and 14 were predicted to be persistent. The six highest-priority TPs originated from the tetracycline antibiotic family and antivirals. This review, and in particular our ranking of antimicrobial TPs of concern, can support authorities in planning related intervention strategies and source mitigation of antimicrobials toward a sustainable future.

Antiviral drugs in wastewater are on the rise as emerging contaminants: A comprehensive review of spatiotemporal characteristics, removal technologies and environmental risks

Antiviral drugs (ATVs) are widely used to treat illnesses caused by viruses. Particularly, ATVs were consumed in such large quantities during the pandemic that high concentrations were detected in wastewater and aquatic environment. Since ATVs are not fully absorbed by the human or animal body, this results in large amounts of them being discharged into the sewage through urine or feces. Most ATVs can be degraded by microbes at wastewater treatment plants (WWTPs), while some ATVs either require deep treatment to reduce concentration and toxicity. Parent and metabolites residing in effluent posed a varying degree of risk when entering the aquatic environment, while increasing the potential of natural reservoirs for environmentally acquired antiviral drug resistance potential. There is a rising research on the behavior of ATVs in the environment has surged since the pandemic. In the context of multiple viral diseases worldwide, especially during the current COVID-19 pandemic, a comprehensive assessment of the occurrence, removal, and risk of ATVs is urgently needed. This review aims to discuss the fate of ATVs in WWTPs from various regions in the world with wastewater as the main analyzing object. The ultimate goal is to focus on ATVs with high ecological impact and regulate their use or develop advanced treatment technologies to mitigate the risk to the environment.

Three-dimensional heterogeneous electro-Fenton system with reduced graphene oxide based particle electrode for Acyclovir removal

New pollutant pharmaceutical and personal care products (PPCPs), especially antiviral drugs, have received increasing attention not only due to their increase in usage after the outbreak of COVID-19 epidemics but also due to their adverse impacts on water ecological environment. Electro-Fenton technology is an effective method to remove PPCPs from water. Novel particle electrodes (MMT/rGO/Fe₃O₄) were synthesized by depositing Fe₃O₄ nanoparticles on reduced graphene oxide modified montmorillonite and acted as catalysts to promote oxidation performance in a three-dimensional Electro-Fenton (3D-EF) system. The electrodes combined the catalytic property of Fe₃O₄, hydrophilicity of montmorillonite and electrical conductivity of graphene oxides, and applied for the degradation of Acyclovir (ACV) with high efficiency and ease of operation. At optimal condition, the degradation rate of ACV reached 100% within 120 min, and the applicable pH range could be 3 to 11 in the 3D-EF system. The stability and reusability of MMT/rGO/Fe₃O₄ particle electrodes were also studied, the removal rate of ACV remained at 92% after 10 cycles, which was just slightly lower than that of the first cycle. Potential degradation mechanisms were also proposed by methanol quenching tests and FT-ICR-MS.

Evaluation of acyclovir adsorption on granular activated carbon from aqueous solutions: batch and fixed-bed parametric studies

The present study is aimed to assess the adsorptive potential of carbonaceous material for the acyclovir (ACVR) removal from the aquatic environment using batch and fixed-bed processes. In batch mode, the impact of various process conditions (contact time, pH, adsorbent dose, initial ACVR concentration, and temperature) on ACVR adsorption was investigated. Experimental results revealed that Langmuir isotherm and the pseudo-second-order kinetic model adequately represent the ACVR adsorption mechanism, indicating homogeneous adsorption. The process was found exothermic and spontaneous. Thermodynamic studies concluded that adsorption is a result of both physisorption and chemisorption. To understand the dynamic regime for the design of large-scale column studies, experimental data obtained from breakthrough curve were fitted to various analytical kinetic models. Yan model followed by Thomas model demonstrated a greater correlation of breakthrough data, confirming that the results are significant and are in line with Langmuir isotherm and pseudo-second-order kinetic. G-AC exhibits sufficient adsorption capacity for ACVR. Hence, it is concluded that it can be used in a fixed-bed column in continuous mode for the treatment of ACVR-contaminated wastewater.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-023-02810-7.

Comparison of ribavirin degradation in the UV/H2O2 and UV/PDS systems: Reaction mechanism, operational parameter and toxicity evaluation

Residues in surface water of ribavirin, which used extensively during the COVID-19 pandemic, have become an emerging issue due to its adverse impact on the environment and human health. UV/H₂O₂ and UV/peroxydisulfate (PDS) have different degradation effects on ribavirin, and the same operational parameter have different effects on the two processes. In this study, the reaction mechanism and degradation efficiency for ribavirin were studied to compare the differences under UV/H₂O₂ and UV/PDS processes. We calculated the total rate constants of ribavirin with HO^• and SO₄ ^•- in the liquid phase as 2.73 × 10⁸ and 9.39 × 10⁵ M^-1s^-1. The density functional theory (DFT) calculation results showed that HO^• and SO₄ ^•- react more readily with ribavirin via H-abstraction (HAA). The nitrogen-containing heterocyclic ring is difficult to undergo ring-opening degradation. The UV/PDS process was more stable and performed better than the UV/H₂O₂ for the ribavirin degradation when the same molar oxidant dosage was applied. HO^• plays an extremely important role in the degradation of ribavirin by UV/PDS. The reason for this phenomenon is the combination of the higher yield of HO^• produced in the UV/PDS process and the faster reaction rate of ribavirin with HO^•. The UV/H₂O₂ process is more sensitive to pH than UV/PDS. Alkaline condition can significantly inhibit the ribavirin degradation. The effects of natural organic matter (NOM) and ribavirin concentration were also compared. Eventually, the toxicity prediction of the product showed that the opening-ring products were more toxic than the parent compound.

Evaluating the "wrong-way-round" electrospray ionization of antiretroviral drugs for improved detection sensitivity

The presence of antiretroviral drugs (ARVDs) in the aquatic environment poses a significant health risk to the ecosystem. The dilution of these compounds during wastewater treatment processes, followed by discharge into the environment, results in extremely low concentrations in the range of ng/L. Therefore, to enable detection of these low concentrations, it is important to determine the most efficient electrospray ionization (ESI) mode using the right mobile phase modifier and to establish a selective extraction procedure. In this study, we compared the ESI intensity in the positive and negative mode using both formic acid (FA) and ammonium hydroxide (NH₄OH) as mobile phase modifiers. The results revealed a phenomenon known as the "wrong-way-round" (WWR) ESI in which high intensity [M + H]⁺ ions were detected under basic conditions using NH₄OH as modifier and, similarly, high intensity [M-H]^- ions were detected under acidic conditions using FA as modifier. Furthermore, mixed-mode strong cation (MCX) and mixed-mode strong anion (MAX) exchange sorbents were evaluated for extraction recoveries, which yielded extraction recoveries between 60 and 100%. Finally, the recoveries obtained using mixed-mode ion exchange sorbents compared to ion production during the ESI process provide evidence that ions produced in solution do not necessarily reflect the ions that are produced during the ESI process. Based on the results of this study, it is recommended to evaluate the optimal ionization mode under basic and acidic conditions, instead of defaulting to the use of acidic modifiers with positive ion detection.

Biocatalyst developed with recovered iron-rich minerals enhances the biotransformation of SARS-CoV-2 antiviral drugs in anaerobic bioreactors

The biotransformation of the SARS-CoV-2 antiviral drugs, ribavirin and tenofovir, was studied in methanogenic bioreactors. The role of iron-rich minerals, recovered from a metallurgic effluent, on the biotransformation process was also assessed. Enrichment of anaerobic sludge with recovered minerals promoted superior removal efficiency for both antivirals (97.4 % and 94.7 % for ribavirin and tenofovir, respectively) as compared to the control bioreactor lacking minerals, which achieved 58.5 % and 37.9 % removal for the same drugs, respectively. Further analysis conducted by liquid chromatography coupled to mass spectroscopy revealed several metabolites derived from the biotransformation of both antivirals. Interestingly, tracer analysis with ¹³CH₄ revealed that anaerobic methane oxidation coupled to Fe(III) reduction occurred in the enriched bioreactor, which was reflected in a lower content of methane in the biogas produced from this system, as compared to the control bioreactor. This treatment proposal is suitable within the circular economy concept, in which recovered metals from an industrial wastewater are applied in bioreactors to create a biocatalyst for promoting the biotransformation of emerging pollutants. This strategy may be appropriate for the anaerobic treatment of wastewaters originated from hospitals, as well as from the pharmaceutical and chemical sectors.

Evaluation of degradation performance toward antiviral drug ribavirin using advanced oxidation process and its relations to ecotoxicity evolution

The rapid spread of coronavirus disease 2019 has increased the consumption of some antiviral drugs, wherein these are discharged into wastewater, posing risks to the ecosystem and human health. Therefore, efforts are being made for the development of advanced oxidation processes (AOPs) to remediate water containing these pharmaceuticals. Here, the toxicity evolution of the antiviral drug ribavirin (RBV) was systematically investigated during its degradation via the UV/TiO₂/H₂O₂ advanced oxidation process. Under optimal conditions, RBV was almost completely eliminated within 20 min, although the mineralization rate was inadequate. Zebrafish embryo testing revealed that the ecotoxicity of the treated RBV solutions increased at some stages and decreased as the reaction time increased, which may be attributed to the formation and decomposition of various transformation products (TPs). Liquid chromatography-mass spectrometry analysis along with density functional theory calculations helped identify possible toxicity increase-causing TPs, and quantitative structure activity relationship prediction revealed that most TPs exhibit higher toxicity than the parent compound. The findings of this study suggest that, in addition to the removal rate of organics, the potential ecotoxicity of treated effluents should also be considered when AOPs are applied in wastewater treatment.

Polystyrene microplastic particles in combination with pesticides and antiviral drugs: Toxicity and genotoxicity in Ceriodaphnia dubia

Freshwater ecosystems are recognized as non-negligible sources of plastic contamination for the marine environment that is the final acceptor of 53 thousand tons of plastic per year. In this context, microplastic particles are well known to directly pose a great threat to freshwater organisms, they also indirectly affect the aquatic ecosystem by adsorbing and acting as a vector for the transport of other pollutants ("Trojan horse effect"). Polystyrene is one of the most widely produced plastics on a global scale, and it is among the most abundant microplastic particles found in freshwaters. Nevertheless, to date few studies have focused on the eco-genotoxic effects on freshwater organisms caused by polystyrene microplastic particles (PS-MPs) in combination with other pollutants such as pharmaceuticals and pesticides. The aim of this study is to investigate chronic and sub-chronic effects of the microplastic polystyrene beads (PS-MP, 1.0 μm) both as individual xenobiotic and in combination (binary/ternary mixtures) with the acicloguanosine antiviral drug acyclovir (AC), and the neonicotinoid broad-spectrum insecticide imidacloprid (IMD) in one of the most sensitive non-target organisms of the freshwater food chain: the cladoceran crustacean Ceriodaphnia dubia. Considering that the individually selected xenobiotics have different modes of action and/or different biological sites, the Bliss independence was used as reference model for this research. Basically, when C. dubia neonates were exposed for 24 h to the mixtures during Comet assay, mostly an antagonistic genotoxic effect was observed. When neonates were exposed to the mixtures for 7 days, mostly an additive chronic toxic effect occurred at concentrations very close or even overlapping to the environmental ones ranging from units to tens of ng/L for PS-MPs, from tenths/hundredths to units of μg/L for AC and from units to hundreds of μg/L for IMD, revealing great environmental concern.

Hazardous drugs (NIOSH's list-group 1) in healthcare settings: Also a hazard for the environment?

Healthcare workers can be exposed to dangerous drugs during their daily practice. The National Institute for Occupational Safety and Health (NIOSH) considers "hazardous drugs" as those that had shown one or more of the following characteristic in studies with animals, humans or in vitro systems: carcinogenicity, teratogenicity or other toxicity for development, reproductive toxicity, organ toxicity at low doses, or genotoxicity. In the actual list (draft list 2020), drugs classified in group 1 are those with carcinogenic effects. Moreover, the global human and veterinary cancer is expected to grow, so antineoplastic drug consumption may consequently grow, leading to an increase of anticancer pharmaceuticals in the environment. Not all drugs pertaining to group 1 can be classified as "antineoplastic" or "cytostatic". Since most of the research on environment presence and ecotoxicological effects of pharmaceuticals has been focused on this therapeutic class, other carcinogenic drugs belonging to different therapeutic groups may have been omitted in previous studies. In this study we aim to review the presence in the environment of the hazardous drugs (NIOSH group 1) and their possible environmental impact. Of the 90 drugs considered, there is evidence of presence in the environment for 19. Drugs with more studies reporting positive detections are: the antibiotic chloramphenicol (55), the alkylating agents cyclophosphamide (39) and ifosfamide (30), and the estrogen receptor modulator tamoxifen (18). Although the original purpose of the NIOSH list and related documents is to provide guidance to healthcare professionals in order to adequately protect them from the hazards posed by these drugs in healthcare settings, we believe they can be useful for environmentalists too. Absence of data regarding the potential of environmental risk of certain hazardous drugs might tell us which drugs ought to be prioritized in the future.

Pharmaceutical compounds used in the COVID-19 pandemic: A review of their presence in water and treatment techniques for their elimination

During the COVID-19 pandemic, high consumption of antivirals, antibiotics, antiparasitics, antiprotozoals, and glucocorticoids used in the treatment of this virus has been reported. Conventional treatment systems fail to efficiently remove these contaminants from water, becoming an emerging concern from the environmental field. Therefore, the objective of the present work is to address the current state of the literature on the presence and removal processes of these drugs from water bodies. It was found that the concentration of most of the drugs used in the treatment of COVID-19 increased during the pandemic in water bodies. Before the pandemic, Azithromycin concentrations in surface waters were reported to be in the order of 4.3 ng L^-1, and during the pandemic, they increased up to 935 ng L^-1. Laboratory scale studies conclude that adsorption and advanced oxidation processes (AOPs) can be effective in the removal of these drugs. Up to more than 80% removal of Azithromycin, Chloroquine, Ivermectin, and Dexamethasone in aqueous solutions have been reported using these processes. Pilot-scale tests achieved 100% removal of Azithromycin from hospital wastewater by adsorption with powdered activated carbon. At full scale, treatment plants supplemented with ozonation and artificial wetlands removed all Favipiravir and Azithromycin, respectively. It should be noted that hybrid technologies can improve removal rates, process kinetics, and treatment cost. Consequently, the development of new materials that can act synergistically in technically and economically sustainable treatments is required.

Environmental and human health risk assessment of mixture of Covid-19 treating pharmaceutical drugs in environmental waters

This study identified ecological and human health risks exposure of COVID-19 pharmaceuticals and their metabolites in environmental waters. Environmental concentrations in aquatic species were predicted using surface water concentrations of pharmaceutical compounds. Predicted No-Effect Concentrations (PNEC) in aquatic organisms (green algae, daphnia, and fish) was estimated using EC₅₀/LC₅₀ values of pharmaceutical compounds taken from USEPA ECOSAR database. PNEC for human health risks was calculated using the acceptable daily intake values of drugs. Ecological PNEC revealed comparatively high values in algae (Chronic toxicity PNEC values, high to low: ribavirin (2.65 × 10⁵ μg/L) to ritonavir (2.3 × 10^-1 μg/L)) than daphnia and fish. Risk quotient (RQ) analysis revealed that algae (Avg. = 2.81 × 10⁴) appeared to be the most sensitive species to pharmaceutical drugs followed by daphnia (Avg.: 1.28 × 10⁴) and fish (Avg.: 1.028 × 10³). Amongst the COVID-19 metabolites, lopinavir metabolites posed major risk to aquatic species. Ritonavir (RQ = 6.55) is the major drug responsible for human health risk through consumption of food (in the form fish) grown in pharmaceutically contaminated waters. Mixture toxicity analysis of drugs revealed that algae are the most vulnerable species amongst the three trophic levels. Maximum allowable concentration level for mixture of pharmaceuticals was found to be 0.53 mg/L.

HIV-antiretrovirals in river water from Gauteng, South Africa: Mixed messages of wastewater inflows as source

South Africa has the highest number of people living with the human immunodeficiency virus (HIV). High usage of HIV-antiretroviral drugs (ARVs) for the treatment of the acquired immunodeficiency syndrome (AIDS) leads to the presence of ARVs in the environment. Wastewater is a major contributor of pharmaceuticals in surface and drinking water as wastewater treatment plants (WWTPs) are not designed to remove these compounds. Pharmaceuticals in the environment pose risks and the effects of ARVs on non-target organisms are largely unknown. The concentrations of ARVs in surface water upstream and downstream from WWTPs in rivers were determined. The samples were extracted by solid-phase extraction and analysed by using liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. Five ARVs were quantified, mostly in downstream samples of the WWTPs, indicating wastewater as a source of ARVs, but this was not apparent in all cases. Nevirapine, lopinavir, and efavirenz were frequently detected; the highest concentrations being lopinavir and efavirenz at 38 μg/L and 24 μg/L, respectively. Aquatic ecosystems are at risk due to the constant input of pharmaceuticals that include large amounts of everyday use and the release of ARVs. This study highlights the potential of increased water pollution worldwide should more people consume increased quantities of pharmaceuticals.

Antiretroviral Drugs in African Surface Waters: Prevalence, Analysis, and Potential Remediation

The sources, ecotoxicological impact, and potential remediation strategies of antiretroviral drugs (ARVDs) as emerging contaminants in surface waters are reviewed based on recent literature. The occurrence of ARVDs in water bodies raises concern because many communities in Africa depend on rivers for water resources. Southern Africa is a potential hotspot regarding ARVD contamination due to relatively high therapeutic application and detection thereof in water bodies. Efavirenz and nevirapine are the most persistent in effluents and are prevalent in surface water based on environmental concentrations. Whereas the highest concentration of efavirenz reported in Kenya was 12.4 µg L^-1 , concentrations as high as 119 and 140 µg L^-1 have been reported in Zambia and South Africa, respectively. Concentrations of ARVDs ranging from 670 to 34 000 ng L^-1 (influents) and 540 to 34 000 ng L^-1 (effluents) were determined in wastewater treatment plants in South Africa, compared with Europe, where reported concentrations range from less than limit of detection (LOD) to 32 ng L^-1 (influents) and less than LOD to 22 ng L^-1 (effluents). The present African-based review suggests the need for comprehensive toxicological and risk assessment of these emerging pollutants in Africa, with the intent of averting environmental hazards and the development of sustainable remediation strategies. Environ Toxicol Chem 2022;41:247-262. © 2021 SETAC.

Occurrence, removal and mass loads of antiviral drugs in seven wastewater treatment plants with various treatment processes

Antiviral drugs are among the most common and important classes of pharmaceuticals to treat viral infections, however their continuous emission and persistence in the receiving environment has attracted increasing attention about their potential ecological risks. Here we investigated the occurrence, fate and mass load of 9 antiviral drugs for acquired immunodeficiency syndrome and hepatitis B, in 7 wastewater treatment plants (WWTPs) with different treatment processes in Guangdong, China. Totally, 8 target antiviral drugs were detected in the WWTPs influent wastewater, effluent wastewater and sludge, with maximal concentrations up to 7624 ng/L (telbivudine), 568 ng/L (telbivudine), and 2013 ng/g wet weight (telbivudine), respectively. The removal efficiency varied widely between different antiviral drugs, with the mean aqueous removal efficiency and total removal efficiency ranging from -6.2% (nevirapine) to 100% (lamivudine) and -1.2% (nevirapine) to 100% (lamivudine), respectively. Mass balance analysis showed that their elimination was mostly attributed to the biodegradation/biotransformation. The total back-estimated usage and emission of 9 target antiviral drugs were 77.8 t/y and 13.2 t/y in Guangdong province, China, respectively. Based on the sewage epidemiology approach, the consumption and emission of antiviral drugs in seven studied WWTPs were ranged at 2.31 mg/d/1000 people (nevirapine) to 4970 mg/d/1000 people (telbivudine), and 0 (lamivudine) to 900 mg/d/1000 people (telbivudine), respectively. Preliminary risk assessment showed that the antiviral drugs of zidovudine, ritonavir, lopinavir, and telbivudine in the receiving rivers could pose high ecological risks for aquatic environment. The findings from the present study illustrate the persistence of nevirapine in WWTPs, and provide essential evidence for further study into the development of wastewater treatment technologies.

Transformation of antiviral ribavirin during ozone/PMS intensified disinfection amid COVID-19 pandemic

Due to the spread of coronavirus disease 2019 (COVID-19), large amounts of antivirals were consumed and released into wastewater, posing risks to the ecosystem and human health. Ozonation is commonly utilized as pre-oxidation process to enhance the disinfection of hospital wastewater during COVID-19 spread. In this study, the transformation of ribavirin, antiviral for COVID-19, during ozone/PMS‑chlorine intensified disinfection process was investigated. •OH followed by O₃ accounted for the dominant ribavirin degradation in most conditions due to higher reaction rate constant between ribavirin and •OH vs. SO₄•^- (1.9 × 10⁹ vs. 7.9 × 10⁷ M^-1 s^-1, respectively). During the O₃/PMS process, ribavirin was dehydrogenated at the hydroxyl groups first, then lost the amide or the methanol group. Chloride at low concentrations (e.g., 0.5- 2 mg/L) slightly accelerated ribavirin degradation, while bromide, iodide, bicarbonate, and dissolved organic matter all reduced the degradation efficiency. In the presence of bromide, O₃/PMS process resulted in the formation of organic brominated oxidation by-products (OBPs), the concentration of which increased with increasing bromide dosage. However, the formation of halogenated OBPs was negligible when chloride or iodide existed. Compared to the O₃/H₂O₂ process, the concentration of brominated OBPs was significantly higher after ozonation or the O₃/PMS process. This study suggests that the potential risks of the organic brominated OBPs should be taken into consideration when ozonation and ozone-based processes are used to enhance disinfection in the presence of bromide amid COVID-19 pandemic.

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

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

Predicted occurrence, ecotoxicological risk and environmentally acquired resistance of antiviral drugs associated with COVID-19 in environmental waters

Antiviral drugs have been used to treat the ever-growing number of coronavirus disease, 2019 (COVID-19) patients. Consequently, unprecedented amounts of such drug residues discharging into ambient waters raise concerns on the potential ecotoxicological effects to aquatic lives, as well as development of antiviral drug-resistance in wildlife. Here, we estimated the occurrence, fate and ecotoxicological risk of 11 therapeutic agents suggested as drugs for COVID-19 treatment and their 13 metabolites in wastewater and environmental waters, based on drug consumption, physical-chemical property, and ecotoxicological and pharmacological data for the drugs, with the aid of quantitative structure-activity relationship (QSAR) modelling. Our results suggest that the removal efficiencies at conventional wastewater treatment plants will remain low (<20%) for half of the substances, and consequently, high drug residues (e.g. 7402 ng/L ribavirin, 4231 ng/L favipiravir, 730 ng/L lopinavir, 319 ng/L remdesivir; each combined for both unchanged forms and metabolites; and when each drug is administered to 100 patients out of 100,000 populations on a day) can be present in secondary effluents and persist in the environmental waters. Ecotoxicological risk in receiving river waters can be high (risk quotient >1) by a use of favipiravir, lopinavir, umifenovir and ritonavir, and medium (risk quotient >0.1) by a use of chloroquine, hydroxychloroquine, remdesivir, and ribavirin, while the risk will remain low (risk quotient <0.1) for dexamethasone and oseltamivir. The potential of wild animals acquiring antiviral drug resistance was estimated to be low. Our prediction suggests a pressing need for proper usage and waste management of antiviral drugs as well as for improving removal efficiencies of drug residues in wastewater.

Risk assessment and investigation of landfill leachate as a source of emerging organic contaminants to the surrounding environment: a case study of the largest landfill in Jinan City, China

Emerging organic contaminants (EOCs) have been widely studied in landfill leachates but not in the surrounding environment of landfills. In this study, two sampling campaigns were conducted to determine 45 EOCs in landfill leachates and environmental samples near a landfill in East China. Our study focused on the seasonal occurrence and spatial distribution of the target EOCs, as well as their ecological risks. The results showed 13 out of 45 EOCs were detectable and achieved individual concentrations that ranged from 2.0 to 5080 ng/L in the landfill leachates. Most of the detected EOCs exhibited higher concentrations in the leachates collected in summer than in winter. Effective removal of the EOCs by a two-stage disc tube reverse osmosis (DTRO) system led to a significant reduction in their concentration levels (< LOQ ~ 49 ng/L) in treated leachates. Eight EOCs (< LOQ ~ 62.7 ng/L) were detected in the groundwater adjacent to the landfill and had a similar composition pattern to raw leachates. The contamination levels of the target EOCs in groundwater decreased with the distance of sampling sites from the landfill. In soil samples, the occurrence of target EOCs was not consistent with raw or treated landfill leachates. Spatially, no apparent difference in the EOC concentrations was observed in the soil nearby the landfill. Crop plants sorbed the EOCs contained in soil (< LOQ ~ 30.4 ng/L), but they were not able to bioconcentrate the contaminants in either roots or edible parts. Risk assessment suggested that the individual EOC likely posed medium to high risks to aquatic organisms in groundwater while negligible impacts to human health through consumption of vegetables. To the best of our knowledge, this is the first report on the contribution of landfill leachates to EOC contamination in both aquatic and soil environments in East China. Our findings emphasized the importance of investigating EOCs in landfill leachates and accumulative environmental risks of EOCs in the neighboring environment of landfills in China.

Emerging contaminants in South African water environment- a critical review of their occurrence, sources and ecotoxicological risks

The release of emerging contaminants (ECs) to the environment is a serious concern due to its health implications on humans, aquatic species, and the development of anti-microbial resistance. This review focuses on the critical analysis of available literature on the prevalence of ECs in the aquatic environment and their removal from wastewater treatment plants (WWTPs) in South Africa. Besides, a risk assessment is performed on the reported ECs from the South African surface water to augment the knowledge towards mitigation of EC pollution, and prioritisation of ECs to assist future monitoring plans and regulation framework. A zone wise classification approach was carried out to identify the spatial inferences and data deficiencies that revealed a non-uniformity in the monitoring of ECs throughout South Africa, with few zones rendering no data. The overarching data mining further revealed that unmanaged urine diverted toilets could be a potential source of EC pollution to groundwater in South Africa. Based on the available literature, it can be deduced that the complete adoption of EC management practices from developed countries might only contribute partly in the mitigation of EC pollution in South Africa. Therefore, an EC monitoring programme specific to the country is recommended which should be based on their occurrence levels, sources and removal in WWTPs.

Application of multi-parameter population model based on endogenous population biomarkers and flow volume in wastewater epidemiology

The consumption or prevalence of acesulfame, caffeine, paracetamol and amantadine was estimated by wastewater-based epidemiology based on a multi-parameter population model in 20 sewage treatment plants (STPs) in Hebei province, China. To minimize the uncertainties contributed by population estimation in WBE, a multi-parameter population model was established based on the population biomarkers equivalent population and flow volume-population with the weight factors calculated by the analytic hierarchy process (AHP). 4-Pyridoxic acid (4-PA), cotinine, trans-3'-hydroxycotinine (trans-3'-OH-Cot) and 1,4-methylimidazole acetic acid (MIAA) were selected as population biomarkers. The estimated model population showed the highest correlations (r² = 0.97, p < 0.01) and lowest variation (one way-ANOVA, p = 0.82, mean variation: -0.1%) comparing to the census data, suggestion better population estimation. The estimated consumption of acesulfame, caffeine, paracetamol and amantadine was 6.7 ± 2.4 mg/day/inh, 50.5 ± 38.5 mg/day/inh, 61.5 ± 52.7 mg/day/inh and 0.52 ± 0.33 mg/day/inh, respectively. Meanwhile, the prevalence of paracetamol and amantadine was calculated to be 5.3% ± 4.5% and 0.28% ± 0.18%, respectively. The estimated results were consistent with that of previous researches in China and were also in accordance with the consumption calculated by sales data (acesulfame and paracetamol). Moreover, uncertainty study showed decrease in population-associated uncertainties by using a multi-parameter population model. The results demonstrated that the multi-parameter population model constructed in this research is feasible to apply in WBE and might lead to lower uncertainties in population estimation.

A chronicle of SARS-CoV-2: Seasonality, environmental fate, transport, inactivation, and antiviral drug resistance

In this review, we present the environmental perspectives of the viruses and antiviral drugs related to SARS-CoV-2. The present review paper discusses occurrence, fate, transport, susceptibility, and inactivation mechanisms of viruses in the environment as well as environmental occurrence and fate of antiviral drugs, and prospects (prevalence and occurrence) of antiviral drug resistance (both antiviral drug resistant viruses and antiviral resistance in the human). During winter, the number of viral disease cases and environmental occurrence of antiviral drug surge due to various biotic and abiotic factors such as transmission pathways, human behaviour, susceptibility, and immunity as well as cold climatic conditions. Adsorption and persistence critically determine the fate and transport of viruses in the environment. Inactivation and disinfection of virus include UV, alcohol, and other chemical-base methods but the susceptibility of virus against these methods varies. Wastewater treatment plants (WWTPs) are major reserviors of antiviral drugs and their metabolites and transformation products. Ecotoxicity of antiviral drug residues against aquatic organisms have been reported, however more threatening is the development of antiviral resistance, both in humans and in wild animal reservoirs. In particular, emergence of antiviral drug-resistant viruses via exposure of wild animals to high loads of antiviral residues during the current pandemic needs further evaluation.

Prospects and challenges of photocatalysis for degradation and mineralization of antiviral drugs

Among the outbreak of influenza and other pandemics such as SARS-CoV-2 recently over the globe, antiviral drugs were significantly concerned with controlling the disease and these pandemics. They have been developed for seven decades around more than 90 drugs categorized licensed to treat nine human infectious diseases. Based on their functional group, antiviral compounds will mitigate infectivity and symptoms and reduce the illness period by arresting the viral replication cycle at different stages. Antiviral drugs have been developed complexly and met many biothreat challenges due to their high biosafety level requirement. In recent years, the spreading of novel virus strains that are a threat to human life, the development in researching and manufacturing new types of antiviral drugs increases and the use by patients and clinicians have increased. Antiviral compounds have been reported only partly removed during wastewater treatment. They were available in wastewater treatment plant effluents and found in surface water from rivers and streams, underground water, and even in drinking water. Photocatalytic degradation of antiviral drugs was exploding to clear the environmental waters from the antiviral drugs. The principle of photocatalysis is based on the excitation of the catalyst material by irradiation of light. The catalyst produces free radicals under the action of photons, which will destroy the pollutants adsorbed on its surface. The photocatalytic degradation mechanism of antiviral drugs can be understood through decomposing in a heterogeneous photocatalytic system and which species are involved in the active decomposition of the drug and then photocatalytically degrading into intermediates or mineralization products. The intermediates and the reaction pathway of antiviral compound photocatalytic degradation are complicated. However, some of the degradation processes are complete, and inorganic compounds (CO₂ and H₂O) are their final products.

Is Disposal of Unused Pharmaceuticals as Municipal Solid Waste by Landfilling a Good Option? A Case Study in China

Properly disposing of unused pharmaceuticals is essential to minimize emissions of active pharmaceutical ingredients (APIs). The aim of this study was to determine whether disposing of unused pharmaceuticals in household solid waste is a cost-effective way of attenuating pharmaceutical emissions. We calculated attenuation rates (ARs) for unused pharmaceuticals by performing mass balance calculations for disposal to landfill. The results indicated that the average ARs for disposal as household solid waste reached 63% to 100% for our investigated pharmaceuticals at the worst scenario, indicating that disposal as household solid waste strongly attenuated emissions of APIs. Disposing of unused pharmaceuticals as household solid waste could be a cost-effective disposal method from the view of reducing APIs emission, but should be used with caution.

Municipal Solid Waste Landfills: An Underestimated Source of Pharmaceutical and Personal Care Products in the Water Environment

Pharmaceutical and personal care products (PPCPs) have been the focus of increasing concern in recent decades due to their ubiquity in the environment and potential risks. Out-of-date PPCPs are usually discharged into municipal solid wastes (MSWs), enter the leachates in MSW landfills, and have serious adverse effects on the surrounding water environment. However, the occurrence and removal of PPCPs from landfill leachates have rarely been examined to date. This lack of knowledge makes the landfill an underestimated source of PPCPs in the environment. In this review, we collected the relevant publications of PPCPs in landfill leachates, systematically summarized the occurrence of PPCPs in landfill leachates globally, evaluated the removal performances for various PPCPs by different types of on-site full-scale leachate treatment processes, and assessed the impacts of landfill leachates on PPCPs in the adjacent groundwater. In particular, influencing factors for PPCPs in landfill leachates, including the physicochemical properties of PPCPs, climate conditions, and characteristics of landfill sites (i.e., landfill ages) as well as sociological factors (i.e., economic development), were extensively discussed to understand their occurrence patterns. Future perspectives were also proposed in light of the identified knowledge gaps. To the best of our knowledge, this is the first review regarding the occurrence and removal of PPCPs from landfill leachates worldwide.

Impact of long-term parental exposure to Tamiflu metabolites on the development medaka offspring (Oryzias latipes)

Despite the widespread use of the antiviral drug, Tamiflu®, little is known about the long-term toxic effects of drug or its metabolites in an aquatic ecosystem. This study integrated epidemiological and ecotoxicological methods to determine environmentally relevant concentrations of Tamiflu. A model based on the species medaka (Oryzias latipes) was then used to determine the health status and reproductivity of adults exposed to the drug as well as the embryonic development of offspring. The proposed ecotoxicological model was also used to quantitatively and qualitatively evaluate the toxicodynamic parameters related to egg production, hatchability, and development. Our results revealed that at an environmentally relevant exposure, Tamiflu and its metabolites had no adverse effects on growth, survival, or fecundity of adult medaka. Nonetheless, we observed a reduction in hatchability under exposure to 300 μg L^-1 and a reduction in body length under exposure exceeding 90 μg L^-1. Under exposure to 300 μg L^-1, the estimated spawning time to reach 50% of the maximum percentage of cumulative egg production (ET50) far exceeded that of the control group (without exposure to Tamiflu). We also observed a ∼ 3-fold decrease in maximum egg hatching (E_max). Based on an integrated epidemiological and ecotoxicological model, predictions of environmental concentrations of Tamiflu and its metabolites revealed that the influenza subtypes associated with increases in environmental concentrations: A(H3N2) > A(H1N1) > type B (in order of their effects). We also determined that A(H3N2) posed a potential risk to hatchability and development. Note however, the environmental concentrations of Tamiflu and its metabolites in most countries are lower than the effect concentrations derived in this study, indicating no hazards for aquatic environments. We recommend the use of hatchability and embryonic development as indicators in assessing the effects of long-term parental exposure to Tamiflu metabolites.

Bioaccumulation and glutathione S-transferase activity on Rhinella arenarum tadpoles after short-term exposure to antiretrovirals

The aim of the present study was to investigate the bioaccumulation and toxicological effects of four antiretrovirals (lamivudine, stavudine, zidovudine and nevirapine) on Rhinella arenarum tadpoles, after short-term (48 h) exposure to these drugs at sublethal concentrations. The analytical procedure involved a simple extraction method followed by ultra-high performance liquid chromatography with diode array detection and chemometric analysis for data processing. Under the conditions studied, the analytes investigated, particularly nevirapine, showed possible bioaccumulation in tadpoles. Besides, an increase in the bioaccumulation was observed when increasing the exposure concentration. In addition, the enzymatic biomarkers measured to evaluate the toxicological effects showed that acethylcholinesterase activity was similar to that of the control group, while glutathione S-transferase activity was increased, indicating potential oxidative stress damage. Our results also allowed demonstrating the usefulness of chemometric algorithms to quantitate analytes in complex matrices, such as those absorbed by tadpoles in aquatic ecosystems. The results also evidenced the short-term antiretroviral bioaccumulation in tadpoles and the alteration of antioxidant systems, highlighting the need of environmental studies to elucidate the ecotoxicological risk of antiretrovirals in humans and wildlife.

Effects of dissolved organic matter derived from freshwater and seawater on photodegradation of three antiviral drugs

Dissolved organic matter (DOM) is the most important light absorber that may induce indirect photolytic transformation of organic pollutants in natural waters. In this study, effects of DOM derived from freshwater and seawater on the photodegradation of three antiviral drugs acyclovir, lamivudine and zidovudine were investigated. Results show that the photodegradation of acyclovir is promoted mainly by excited triplet states DOM (³DOM*), and the photodegradation of lamivudine is accelerated by ³DOM*, •OH and ¹O₂ together; however, the photodegradation of zidovudine is inhibited by DOM mainly via light screening. Compared with DOM from freshwater, promotion effect of DOM extracted from seawater (SDOM) on the photodegradation of acyclovir and lamivudine is weaker, which is attributed to lower productivity of reactive intermediates. On the other hand, inhibitory effect of SDOM on the photodegradation of zidovudine is also weaker, which is due to weaker light screening caused by lower light absorption. Photodegradation half-lives of the three antiviral drugs are predicted to be all more than 20 days in freshwater and seawater bodies of the Yellow River estuarine region. These findings are significant for understanding the phototransformation processes of antiviral drugs and other organic pollutants in estuarine and coastal regions.

Antiviral drugs in aquatic environment and wastewater treatment plants: A review on occurrence, fate, removal and ecotoxicity

The environmental release of antiviral drugs is of considerable concern due to potential ecosystem alterations and the development of antiviral resistance. As a result, interest on their occurrence and fate in natural and engineered systems has grown substantially in recent years. The main scope of this review is to fill the void of information on the knowledge on the worldwide occurrence of antiviral drugs in wastewaters and natural waters and correlate their levels with their environmental fate. According to the conducted literature survey, few monitoring data exists for several European countries, such as Germany, France, and the UK. Lesser data are available for Asia, where approximately 80% of the studies focus on Japan. Several articles study the occurrence of mostly antiretroantivirals in sub-Saharan African countries, while there is a lack of data for other developing regions of the world, including the rest of Africa, South America, and the biggest part of Asia. An importantly smaller number of studies exists for North America, while no studies exist for Oceania. The against innfluenza drug oseltamivir along with its active carboxy metabolite is found to be the most studied antiviral drug. The distribution of antiviral drugs across all geographic regions varies from low ng L^-1 to high μg L^-1 levels, in some cases, even in surface waters. This overarching review reveals that monitoring of antiviral drugs is necessary, and some of those compounds may require toxicological attention, in the light of either spatial and temporal high concentration or potential antiviral resistance. Based on the information provided herein, the need for a better understanding of the water quality hazards posed by antiviral drugs existence in wastewater outputs and freshwater ecosystems is demosntrated. Finally, the future challenges concerning the occurrence, fate, and potential ecotoxicological risk to organisms posed by antiviral drug residues are discussed.

Porous Ti/SnO2-Sb anode as reactive electrochemical membrane for removing trace antiretroviral drug stavudine from wastewater

Electrochemical degradation of trace antiretroviral drug stavudine was investigated by using a reactive electrochemical membrane (REM) with Ti/SnO₂-Sb anode. From the results it was evident that the stavudine degradation followed pseudo-first-order kinetics, with the values of the degradation rate constant and half-life being 0.24 min^-1 and 2.9 min, respectively, at a current density of 8 mA cm^-2. The degradation rate was obviously decreased under alkaline condition (pH = 11.0) and the degradation was also inhibited in the presence of NO₃^- and Cl^-. Five intermediates were identified in the electrochemical degradation of stavudine, and the degradation pathways were proposed. Density functional theory calculation revealed that the double bond carbon atom nearby hydroxymethyl group was the site attacked by OH and the cleavage of CN bond was the rate-determining step in the electrochemical degradation of stavudine. The nitrogen in stavudine was mainly converted to nitrate and ammonium. Quantitative structure-activity relationship model indicated that the toxicity of some intermediates was higher than the parent compound stavudine. The electric energy consumption for 90% stavudine degradation ranged from 0.87 to 2.29 Wh L^-1 at the experimental conditions, indicating that stavudine can be degraded efficiently by the REM with Ti/SnO₂-Sb anode.

High-efficiency electrochemical degradation of antiviral drug abacavir using a penetration flux porous Ti/SnO2-Sb anode

Electrochemical degradation of antiviral drug abacavir was investigated by using a penetration flux porous Ti/SnO₂-Sb anode prepared by sol-gel method. The effects of applied current density, initial pH, and inorganic anions on the degradation kinetics were systematically studied. Degradation efficiency more than 97% was performed in only 10 min at a current density of 0.2 mA cm^-2. The corresponding degradation rate constant and the lowest electrical energy per order were calculated to be 0.36 min^-1 and 6.5 mWh L^-1, respectively. Extending the reaction duration to 5 h, 53.3% of TOC removal was observed. The results indicated that effective degradation of abacavir appeared in the penetration flux porous Ti/SnO₂-Sb anode with a very low energy consumption. Furthermore, the electrochemical intermediate products and the reaction site during abacavir degradation were detected and recognized. The quantitative structure-activity relationship model revealed that the potential risks of abacavir to the aquatic organism, such as fish, greatly decreased after flowing through the penetration flux porous Ti/SnO₂-Sb anode.

Simultaneous quantification of commonly prescribed antiretroviral drugs and their selected metabolites in aqueous environmental samples by direct injection and solid phase extraction liquid chromatography - tandem mass spectrometry

The widespread implementation of antiretroviral therapy medication has made antiretroviral drugs (ARVDs) a significant pharmaceutical class in regions of high HIV infection rates. However, relatively little is known regarding the environmental occurrence of these emerging contaminants, and this is especially true for their metabolites. In this work, we report analytical methods to study the simultaneous occurrence of a range of common ARVDs and some of their known metabolites in surface water and wastewater. A novel direct injection liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is reported for the analysis of ARVDs of different therapeutic classes and their selected metabolites in wastewater samples. In addition, a solid phase extraction (SPE) procedure was developed for pre-concentration of ARVs and metabolites from surface water samples. The respective methods proved suitable for the quantitative analysis of six parent ARVDs from three ARV classes, as well as three metabolites. Method validation showed average recoveries of 86% for the direct injection method, and 64% for the SPE method. With the exception of Zidovudine and the metabolites of Zidovudine and Ritonavir, all target ARVDs were detected in wastewater samples from two wastewater treatment plants in the Western Cape, South Africa. Higher concentrations were generally measured in influent compared to effluent samples, in the dry compared to the wet season as well as in chlorinated compared to uv-irradiated effluents. This study contributes for the first time quantitative data on the environmental occurrence of the known metabolites of Nevirapine (12-hydroxy-Nevirapine) and Efavirenz (8,14-dihydroxy-Efavirenz).

Experiments and numerical simulation on the degradation processes of carbamazepine and triclosan in surface water: A case study for the Shahe Stream, South China

We examined the occurrence and fate of pharmaceuticals and personal care products in surface water by combining laboratory experiments with numerical simulations. The degradation processes of two typical PPCPs (triclosan and carbamazepine) collected from the Shahe Stream were studied. Hydrolysis, biodegradation, and photolysis were the three major routes of triclosan (TCS) and carbamazepine (CBZ) degradation. A central composite design method was used to investigate the effects of related natural parameters (including pH, dissolved oxygen, salinity, temperature, light intensity, and humic acid) on the TCS and CBZ degradation processes in the laboratory. Our results showed that the main degradation pathway of CBZ and TCS was direct photolysis during the daytime and that the maximal biodegradation rates of CBZ and TCS occurred at 22 °C when the optimum temperature function was used. Based on our experimental results, the observed degradation of CBZ and TCS followed pseudo-first-order kinetics, and the degradation kinetic equations under the influence of multiple natural parameters were established with estimated average degradation rate constants of 1.2452E-7 s^-1 and 3.1260E-5 s^-1 for CBZ and TCS, respectively. The degradation rate constants were incorporated into a one-dimensional, simply integrated hydrodynamic and water quality model. The proposed numerical model was applied to depict the transportation and transformation of CBZ and TCS in surface water and was validated by observational data from the Shahe Stream. The results showed that our model reproduced the observed patterns of CBZ and TCS concentrations reasonably, with slight overestimations compared to the observed data; the relative errors between the simulated and the observed concentrations were 5.85%-6.82% for CBZ and -156.85%--7.18% for TCS. According to our simulation, the spatial distribution of TCS in surface water was determined by biochemical degradation processes that were most affected by temperature under natural conditions; in contrast, the distribution of CBZ was largely controlled by diffusion.

Environmental fate and ecotoxicological effects of antiretrovirals: A current global status and future perspectives

The therapeutic efficacy of antiretroviral drugs as well as challenges and side effects against the human immunodeficiency virus is well documented and reviewed. Evidence is available in literature indication that antiretrovirals are only partially transformed and become completely excreted from the human body in their original form and/or as metabolites in urine and feces. The possibility of massive release of antiretrovirals through human excreta that enters surface water through surface runoff and wastewater treatment plant effluents is now of environmental concern because the public might be experiencing chronic exposure to antiretrovirals. The primary concern of this review is limited data concerning environmental fate and ecotoxicity of antiretrovirals and their metabolites. The review aims to provide a comprehensive insight into the evaluation of antiretrovirals in environmental samples. The objective is therefore to assess the extent of analysis of antiretrovirals in environmental samples and also look at strategies including instrumentation and predictive models that have been reported in literature on the fate and ecotoxicological effects due to presence of antiretrovirals in different environmental compartments. The review also looks at current challenges and offers possible areas of exploration that could help minimize the presence of antiretrovirals in the environment.

LC-MS/MS determination of antiretroviral drugs in influents and effluents from wastewater treatment plants in KwaZulu-Natal, South Africa

South Africa has the largest occurrence of the human immune deficiency virus (HIV) in the world but has also implemented the largest antiretroviral (ARV) treatment programme. It was therefore of interest to determine the presence and concentrations of commonly used antiretroviral drugs (ARVDs) and, also, to determine the capabilities of wastewater treatment plants (WWTPs) for removing ARVDs. To this end, a surrogate standard based LC-MS/MS method was optimized and applied for the detection of thirteen ARVDs used in the treatment and management of HIV/acquired immune deficiency syndrome (HIV/AIDS) in two major and one modular WWTP in the eThekwini Municipality in KwaZulu-Natal, South Africa. The method was validated and the detection limits fell within the range of 2-20 ng L^-1. The analytical recoveries for the ARVDs were mainly greater than 50% with acceptable relative standard deviations. The concentration values ranged from <LOD - 53000 ng L^-1 (influent), <LOD - 34000 ng L^-1 (effluent) in a decentralized wastewater treatment facility (DEWATS); <LOD - 24000 ng L^-1 (influent), <LOD - 33000 ng L^-1 (effluent) in Northern WWTP and 61-34000 ng L^-1 (influent), <LOD - 20000 ng L^-1 (effluent) in Phoenix WWTP. Whilst abacavir, lamivudine and zidovudine were almost completely removed from the effluents, atazanavir, efavirenz, lopinavir and nevirapine persisted in the effluents from all three WWTPs. To estimate the ecotoxicological risks associated with the discharge of ARVDs, a countrywide survey focussing on the occurrence of ARVDs in WWTPs, surface and fresh water bodies, and aquatic organisms, is necessary.

Removal of antiretroviral drugs stavudine and zidovudine in water under UV254 and UV254/H2O2 processes: Quantum yields, kinetics and ecotoxicology assessment

The concentration of antiretroviral drugs in wastewater treatment plants (WWTP) effluents and surface waters of many countries has increased significantly due to their widespread use for HIV treatment. In this study, the removal of stavudine and zidovudine under UV₂₅₄ photolysis or UV₂₅₄/H₂O₂ was investigated in a microcapillary film (MCF) photoreactor, using minimal water samples quantities. The UV₂₅₄ quantum yield of zidovudine, (2.357 ± 0.0589)·10^-2 mol ein^-1 (pH 4.0-8.0), was 28-fold higher that the yield of stavudine (8.34 ± 0.334)·10^-4 mol ein^-1 (pH 6.0-8.0). The second-order rate constant k_OH,iof reaction of hydroxyl radical with the antiretrovirals (UV₂₅₄/H₂O₂ process) were determined by kinetics modeling: (9.98 ± 0.68)·10⁸ M^-1 s^-1 (pH 4.0-8.0) for zidovudine and (2.03 ± 0.18)·10⁹ M^-1 s^-1 (pH 6.0-8.0) for stavudine. A battery of ecotoxicological tests (i.e. inhibition growth, bioluminescence, mutagenic and genotoxic activity) using bacteria (Aliivibrio fischeri, Salmonella typhimurium), crustacean (Daphnia magna) and algae (Raphidocelis subcapitata) revealed a marked influence of the UV dose on the ecotoxicological activity. The UV₂₅₄/H₂O₂ treatment process reduced the ecotoxicological risk associated to direct photolysis of the antiretrovirals aqueous solutions, but required significantly higher UV₂₅₄ doses (≥2000 mJ cm^-2) in comparison to common water UV disinfection processes.

Photodegradation and ecotoxicology of acyclovir in water under UV254 and UV254/H2O2 processes

The photochemical and ecotoxicological fate of acyclovir (ACY) through UV₂₅₄ direct photolysis and in the presence of hydroxyl radicals (UV₂₅₄/H₂O₂ process) were investigated in a microcapillary film (MCF) array photoreactor, which provided ultrarapid and accurate photochemical reaction kinetics. The UVC phototransformation of ACY was found to be unaffected by pH in the range from 4.5 to 8.0 and resembled an apparent autocatalytic reaction. The proposed mechanism included the formation of a photochemical intermediate (ϕ_ACY = (1.62 ± 0.07)·10^-3 mol ein^-1) that further reacted with ACY to form by-products (k' = (5.64 ± 0.03)·10^-3 M^-1 s^-1). The photolysis of ACY in the presence of hydrogen peroxide accelerated the removal of ACY as a result of formation of hydroxyl radicals. The kinetic constant for the reaction of OH radicals with ACY (k_OH/ACY) determined with the kinetic modeling method was (1.23 ± 0.07)·10⁹ M^-1 s^-1 and with the competition kinetics method was (2.30 ± 0.11)·10⁹ M^-1 s^-1 with competition kinetics. The acute and chronic effects of the treated aqueous mixtures on different living organisms (Vibrio fischeri, Raphidocelis subcapitata, D. magna) revealed significantly lower toxicity for the samples treated with UV₂₅₄/H₂O₂ in comparison to those collected during UV₂₅₄ treatment. This result suggests that the addition of moderate quantity of hydrogen peroxide (30-150 mg L^-1) might be a useful strategy to reduce the ecotoxicity of UV₂₅₄ based sanitary engineered systems for water reclamation.

Fate of new three anti-influenza drugs and one prodrug in the water environment

We evaluated the environmental fate of new three anti-influenza drugs, favipiravir (FAV), peramivir (PER), and laninamivir (LAN), and an active prodrug of LAN, laninamivir octanoate (LANO), in comparison with four conventional drugs, oseltamivir (OS), oseltamivir carboxylate (OC), amantadine (AMN), and zanamivir (ZAN) by photodegradation, biodegradation, and sorption to river sediments. In addition, we conducted 9-month survey of urban rivers in the Yodo River basin from 2015 to 2016 (including the influenza season) to investigate the current status of occurrence of these drugs in the river environment. The results clearly showed that FAV and LAN rapidly disappeared through photodegradation (half-lives 1 and 8 h, respectively), followed by LANO which gradually disappeared through biodegradation (half-life, 2 days). The remained PER and conventional drugs were, however, persistent and transported from upstream to downstream sites. Rates of their sorption to river sediments were negligibly small. Detected levels remained were in the range from N.D. to 89 ng/L for the river waters and from N.D. to 906 ng/L in sewage effluent. However, all of the remained drugs were effectively removed by ozonation after chlorination at a sewage treatment plant. These findings suggest the importance of introducing ozonation for reduction of pollution loads in rivers, helping to keep river environments safe. To the best of our knowledge, this is the first evaluation of the removal effects of natural sunlight, biodegradation, and sorption to river sediments on FAV, PER, LAN, LANO, and a conventional drug, AMN.

Identification of transformation products of antiviral drugs formed during biological wastewater treatment and their occurrence in the urban water cycle

The fate of five antiviral drugs (abacavir, emtricitabine, ganciclovir, lamivudine and zidovudine) was investigated in biological wastewater treatment. Investigations of degradation kinetics were accompanied by the elucidation of formed transformation products (TPs) using activated sludge lab experiments and subsequent LC-HRMS analysis. Degradation rate constants ranged between 0.46 L d(-1) gSS(-1) (zidovudine) and 55.8 L d(-1) gSS(-1) (abacavir). Despite these differences of the degradation kinetics, the same main biotransformation reaction was observed for all five compounds: oxidation of the terminal hydroxyl-moiety to the corresponding carboxylic acid (formation of carboxy-TPs). In addition, the oxidation of thioether moieties to sulfoxides was observed for emtricitabine and lamivudine. Antiviral drugs were detected in influents of municipal wastewater treatment plants (WWTPs) with concentrations up to 980 ng L(-1) (emtricitabine), while in WWTP effluents mainly the TPs were found with concentration levels up to 1320 ng L(-1) (carboxy-abacavir). Except of zidovudine none of the original antiviral drugs were detected in German rivers and streams, whereas the concentrations of the TPs ranged from 16 ng L(-1) for carboxy-lamivudine up to 750 ng L(-1) for carboxy-acyclovir. These concentrations indicate an appreciable portion from WWTP effluents present in rivers and streams, as well as the high environmental persistence of the carboxy-TPs. As a result three of the carboxylic TPs were detected in finished drinking water.