Prevalence and sunlight photolysis of controlled and chemotherapeutic drugs in aqueous environments

Insights into the sunlight-Induced photodegradation mechanisms of methamphetamine in surface water driven by NO₃⁻, HCO₃⁻ and Fe3

Psychoactive substances abuse is a global issue, with the methamphetamine (METH) being the most used and produced illicit substance in recent years. METH has been recognized as emerging contaminants in aquatic ecosystems. Research on the removal of METH from surface water is still lacking in-depth exploration. The effects of key aqueous environmental factors on the photodegradation of METH were investigated in this study. NO₃⁻, Fe3+ and dissolved organic matter (DOM) enhanced the photodegradation of METH, respectively, with degradation rates increasing as their concentrations increased. When HCO₃⁻ coexisted with NO₃⁻, it exhibited dual effects on METH photodegradation: low concentrations inhibited the process, whereas high concentrations promoted it. The primary photodegradation products of METH, such as OH-METH, (OH)2-METH, AMP and NO2-OH-METH, were identified. The latter two compounds were newly discovered in this study. The mechanism of NO₃⁻, HCO₃⁻ and Fe3+ accelerating the photodegradation of METH in water was proposed to proceed via the generation of hydroxyl radical (HO∙), leading to the oxidation of METH, along with the involvement of nitro radical (∙NO2) and carbonate radical (CO3•-).

Accumulation of micropollutants, byproducts, and metabolites in vegetables cultivated with treated water

Due to a lack of water resources, people are starting to use treated wastewater to irrigate crops and vegetables. However, the risk of micropollutant exposure from vegetables cultivated with treated wastewater has been largely underestimated. To elucidate this underestimation, a hydroponic system for lettuce cultivation using a nutrient solution spiked with three pharmaceuticals with different log KOW values (acetaminophen (0.46), ketamine (2.18) and methadone (3.93)) was examined, and the total bioconcentration factors (BCFs) (including the transformation of metabolites) of the pharmaceuticals were found to be 0, 120 ± 7.76 and 176 ± 16.0 L/kg, respectively. To simulate treated wastewater, these nutrient solutions were first treated by sunlight photolysis, chlorination, and sunlight/chlorine before use in lettuce cultivation. During the treatment, ketamine and methadone were transformed into norketamine (up to 6.0 %) and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) (up to 16 %), respectively; the BCF of norketamine (162 ± 22.6 L/kg) was found to be even greater than ketamine. In addition, other degradation byproducts (including 3 trace and 13 undetected byproducts in the nutrient solutions) were taken up by the lettuce. In parallel, ketamine and methadone can also undergo metabolism in lettuce; the conversion rate to norketamine increased from 22 ± 7.0 % to 45 ± 0.062 when the ketamine concentration decreased from 1000 to 50 μg/L.

Investigating illicit drug hotspots and daily variations using sewer-network wastewater analysis

Previous wastewater-based epidemiology (WBE) research on illicit drug use has predominantly focused on wastewater treatment plant (WWTP) influents, but information on sewer-network wastewater is very limited. This study represents a pioneering small-scale WBE investigation based on the analysis of sewer-network wastewater samples from different sewer manholes in suburban (Tamsui region) and urban areas (Zhongshan and Wanhua regions) and a comparison of the results with those obtained from corresponding WWTP influents. Among sixteen illicit drugs, methamphetamine exhibited the highest concentration in sewer-network wastewater across both areas. Suburban-urban variations were observed, with more types of illicit drugs detected in the suburban area. Back-calculation indicated that methamphetamine and ketamine were the most-consumed illicit drugs in both sewer-network wastewaters and WWTP influents. Similar types of illicit drugs were detected in the sewer-network wastewaters and WWTP influents, indicating the representativeness of WWTP influents in assessing regional illicit drug abuse. Nevertheless, the sewer-network wastewater results offered additional information making it possible to pinpoint potential hotspots of illicit drug and identify peak usage periods throughout the day, in contrast to the WWTP influent results. In the non-suspected suburban area of Tamsui, high potential hotspots of methamphetamine (sampling points 3 and 6) and ketamine (sampling points 1 and 8) were identified. Although the Zhongshan and Wanhua regions were chosen as suspected hotspots of illicit drug abuse, more severe illicit drug use was observed in Wanhua. Moreover, a trend toward higher illicit drug use from early morning to morning was observed. Despite sampling challenges and higher costs, small-scale WBE via sewer-network wastewater analysis provides superior identification of drug abuse hotspots and peak usage periods. Therefore, this study provides valuable insights for law enforcement and can help prevent and combat illicit drug abuse by targeting potential hotspots and understanding daily illicit drug use dynamics.

Aqueous photolysis of naproxen exposed to UV and natural sunlight: Formation of excited triplet and photosensitizing product

Photochemical transformation is an important attenuation process for the non-steroidal anti-inflammatory drug naproxen (NPX) in both engineered and natural waters. Herein, we investigated the photolysis of NPX in aqueous solution exposed to both ultraviolet (UV, 254 nm) and natural sunlight irradiation. Results show that N2 purging significantly promoted NPX photolysis under UV irradiation, suggesting the formation of excited triplet state (3NPX*) as a critical transient. This inference was supported by benzophenone photosensitization and transient absorption spectra. Sunlight quantum yield of NPX was only one fourteenth of that under UV irradiation, suggesting the wavelength-dependence of NPX photochemistry. 3NPX* formed upon irradiation of NPX underwent photodecarboxylation leading to the formation of 2-(1-hydroxyethyl)-6-methoxynaphthalene (2HE6MN), 2-(1-hydroperoxyethyl)-6-methoxynaphthalene (2HPE6MN), and 2-acetyl-6-methoxynaphthalene (2A6MN). Notably, the conjugation and spin-orbit coupling effects of carbonyl make 2A6MN a potent triplet sensitizer, therefore promoting the photodegradation of the parent NPX. In hospital wastewater, the photolysis of NPX was influenced because the photoproduct 2A6MN and wastewater components could competitively absorb photons. Bioluminescence inhibition assay demonstrated that photoproducts of NPX exhibited higher toxicity than the parent compound. Results of this study provide new insights into the photochemical behaviors of NPX during UV treatment and in sunlit surface waters.

Evaluation of spatial and temporal changes in illicit drug use in the Taipei metropolitan area via wastewater-based epidemiology

Taiwan, identified as pivotal in the Asian drug trafficking chain, has been experiencing a surge in illicit drug-related issues. Wastewater-based epidemiology (WBE) has emerged as a promising approach for comprehensive evaluation of actual illicit drug usage. This study presents the first WBE investigation of illicit drug consumption in Taiwan based on the analysis of wastewater from four wastewater treatment plants (WWTPs) in the Taipei metropolitan area. Additionally, it demonstrates a high correlation between the amounts of illicit drugs seized and influent concentrations over an extended period of time. The reliability of solid-phase extraction and analysis via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was validated for 16 illicit drugs (methamphetamine, ketamine, cocaine, codeine, methadone, morphine, meperidine, fentanyl, sufentanil, para-methoxyamphetamine (PMA), para-methoxymethamphetamine (PMMA), 3,4-methylenedioxymethamphetamine (MDMA), cathinone, methcathinone, mephedrone (MEPH), and 4-methylethcathinone (4-MEC)). Methamphetamine, ketamine, and 4-MEC were consistently detected in all wastewater samples, underscoring their prevalence in the Taipei metropolitan area. Biochemical oxygen demand (BOD) and ammonia nitrogen (ammonia N) were employed to reduce uncertainty in estimations of population size during back-calculation of illicit drug consumption. The results indicate that methamphetamine was the most consumed drug (175-740 mg day-1 1000 people-1), followed by ketamine (22-280 mg day-1 1000 people-1). In addition, urban-related WWTPs exhibited higher consumption of methamphetamine and ketamine than did the suburban-related WWTP, indicating distinct illicit drug usage patterns between suburban and urban regions. Moreover, an examination of temporal trends in wastewater from the Dihua WWTP revealed a persistent predominance of ketamine and methamphetamine, consistent with statistical data pertaining to seizure quantities and urine test results. The study provides encouraging insight into spatial and temporal variations in illicit drug usage in the Taipei metropolitan area, emphasizing the complementary role of WBE in understanding trends in illicit drug abuse.

Stability and Degradation of Opioids in River Water

As the level of consumption of opioids continues to rise globally, there is increasing concern over the potential impacts of continuous opioid discharges into aquatic ecosystems. Opioids are psychoactive compounds that are not completely removed during wastewater treatment, and little is known about their stability and fate in the environment. In the present study, we evaluated the stability of four highly used opioids, buprenorphine, codeine, fentanyl, and tramadol, in river water via batch degradation experiments. The opioids were spiked at environmentally relevant concentrations into 150 mL of river microcosms designed to distinguish among hydrolysis, abiotic degradation, biodegradation, and sorption. All opioids exhibited relatively high stability in river water, with removal rates of only 15% (tramadol) to 26% (buprenorphine) after 6 days. Biodegradation was the most important attenuation pathway for all four opioids, with first-order biodegradation constants ranging from 0.011 d-1 (tramadol) to 0.018 d-1(buprenorphine). Overall, degradation rates were 1-4 orders of magnitude lower compared to the reported rates for wastewater systems. These results offer insights into the stability of opioids in freshwater systems and raise questions about the potential effects of their pseudopresence in surface waters on aquatic organisms.

The male reproductive toxicity after 5-Fluorouracil exposure: DNA damage, oxidative stress, and mitochondrial dysfunction in vitro and in vivo

5-Fluorouracil (5-FU), a chemotherapeutic drug used to treat a variety of cancers, can enter the environment through different routes, causing serious public health and environmental concerns. It has been reported that 5-FU exposure adversely affects male reproductive function, and its effects on this system cannot be avoided. In this study, using western blotting and quantitative polymerase chain reaction studies, we found that 5-FU promoted testicular injury by inducing oxidative stress, which was accompanied by the inhibition of nuclear factor erythroid 2-related factor 2/antioxidant response element signaling. Accumulation of reactive oxygen species (ROS) aggravated 5-FU-mediated mitochondrial dysfunction and apoptosis in murine cell lines and testes, indicating oxidative stress and mitochondrial-dependent apoptotic signaling play crucial roles in the damage of spermatogenic cells caused. N-Acetyl-L-cysteine, an antioxidant that scavenges intracellular ROS, protected spermatogenic cells from 5-FU-induced oxidative damage and mitochondrial dysfunction, revealing the important role of ROS in testicular dysfunction caused by 5-FU. We found that 5-FU exposure induces testicular cell apoptosis through ROS-mediated mitochondria pathway in mice. In summary, our findings revealed the reproductive toxicological effect of 5-FU on mice and its mechanism, provided basic data reference for adverse ecological and human health outcomes associated with 5-FU contamination or poisoning.

Occurrence, ecotoxicity and ecological risks of psychoactive substances in surface waters

Psychoactive substances (PSs) represent a subset of emerging contaminants. Their widespread production and utilization contribute to a growing ecological burden and risk on a global scale. Conventional wastewater treatment methods have proven insufficient in adequately removing psychoactive substances, leading to their occurrence in surface water ecosystems worldwide. As of present, however, a thorough understanding of their geographical prevalence and distribution patterns remains elusive. Further, in the existing literature, there is a scarcity of comprehensive overviews that systematically summarize the toxicity of various psychoactive substances towards aquatic organisms. Through summarizing almost 140 articles, the present study provides an overview of the sources, pollution status, and biotoxicity of psychoactive substances in surface waters, as well as an assessment of their ecological risks. Concentrations of several psychoactive substances in surface waters were found to be as high as hundreds or even thousands of ng·L-1. In parallel, accumulation of psychoactive substances in the tissues or organs of aquatic organisms was found to potentially cause certain adverse effects, including behavioral disorders, organ damage, and DNA changes. Oxidative stress was found to be a significant factor in the toxic effects of psychoactive substances on organisms. The application of the risk quotient approach indicated that psychoactive substances posed a medium to high risk in certain surface water bodies, as well as the need for sustained long-term attention and management strategies.

Illicit Drugs in Surface Waters: How to Get Fish off the Addictive Hook

The United Nations World Drug Report published in 2022 alarmed that the global market of illicit drugs is steadily expanding in space and scale. Substances of abuse are usually perceived in the light of threats to human health and public security, while the environmental aspects of their use and subsequent emissions usually remain less explored. However, as with other human activities, drug production, trade, and consumption of drugs may leave their environmental mark. Therefore, this paper aims to review the occurrence of illicit drugs in surface waters and their bioaccumulation and toxicity in fish. Illicit drugs of different groups, i.e., psychostimulants (methamphetamines/amphetamines, cocaine, and its metabolite benzoylecgonine) and depressants (opioids: morphine, heroin, methadone, fentanyl), can reach the aquatic environment through wastewater discharge as they are often not entirely removed during wastewater treatment processes, resulting in their subsequent circulation in nanomolar concentrations, potentially affecting aquatic biota, including fish. Exposure to such xenobiotics can induce oxidative stress and dysfunction to mitochondrial and lysosomal function, distort locomotion activity by regulating the dopaminergic and glutamatergic systems, increase the predation risk, instigate neurological disorders, disbalance neurotransmission, and produce histopathological alterations in the brain and liver tissues, similar to those described in mammals. Hence, this drugs-related multidimensional harm to fish should be thoroughly investigated in line with environmental protection policies before it is too late. At the same time, selected fish species (e.g., Danio rerio, zebrafish) can be employed as models to study toxic and binge-like effects of psychoactive, illicit compounds.

Biodegradation of sulfoxaflor and photolysis of sulfoxaflor by ultraviolet radiation

Sulfoxaflor (SUL, [N-[methyloxido[1-[6-(trifluoromethyl)-3-pyridinyl] ethyl]-λ4-sulfanylidene] cyanamide]) is a widely used systemic insecticide, and its residue has frequently been detected in the environment, posing a potential threat to the environment. In this study, Pseudaminobacter salicylatoxidans CGMCC 1.17248 rapidly converted SUL into X11719474 via a hydration pathway mediated by two nitrile hydratases (AnhA and AnhB). Extensive (96.4%) degradation of 0.83 mmol/L SUL was achieved by P. salicylatoxidans CGMCC 1.17248 resting cells within 30 min (half-life of SUL 6.4 min). Cell immobilization by entrapment into calcium alginate remediated 82.8% of the SUL in 90 min, and almost no SUL was observed in surface water after incubation for 3 h. P. salicylatoxidans NHases AnhA and AnhB both hydrolyzed SUL to X11719474, although AnhA exhibited much better catalytic performance. The genome sequence of P. salicylatoxidans CGMCC 1.17248 revealed that this strain could efficiently eliminate nitrile-containing insecticides and adapt to harsh environments. We firstly found that UV irradiation transforms SUL to the derivatives X11719474 and X11721061, and the potential reaction pathways were proposed. These results further deepen our understanding of the mechanisms of SUL degradation as well as the environmental fate of SUL.

Engineered tenorite structure of barium-enriched copper oxide for on-site monitoring of cytotoxic methotrexate in environmental samples

Emerging pharmaceutical pollutants pose a threat to both human and environmental health. The removal and monitoring of such pollutants necessitate the use of practical on-site monitoring devices; however, the designs of such devices are underdeveloped. This study involves the fabrication of a low-cost sensor based on barium-incorporated copper oxide (Ba-CuO) for the on-site monitoring of the cytotoxic drug methotrexate (MTRX) in water and sediment samples. The tenorite structure of CuO was slightly enriched with Ba ions at the td sites, distorting the tetrahedron and enhancing its electrochemical properties. Ba-CuO was obtained from Cu(NO₃)₂ and Ba(OH)₂ by a ligand exchange protocol and was characterized using X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis. In addition, the Ba-CuO sensor was tested under various conditions, and it could detect MTRX at concentrations as low as 0.4 nM, with a high sensitivity of 1.3567 µA µM^-1 cm^-2. On-site monitoring yielded recoveries of greater than 93 % from spiked samples, thus exhibiting excellent reproducibility and stability. Therefore, the developed method is practical and has no matrix effect on the MTRX sensor.

Anticancer drugs in wastewater and natural environments: A review on their occurrence, environmental persistence, treatment, and ecological risks

The consumption of anticancer drugs (also known as chemotherapy drugs or antineoplastic drugs) has augmented over the last decades due to increased cancer incidence. Although there is an increasing concern about the presence of pharmaceutical compounds in natural environments and urban/domestic wastewater, anticancer drugs used in chemotherapy and anticancer medication have received less attention. In this review, the occurrence, environmental persistence, and known and potential ecological impacts of anticancer drugs is discussed. This review shows that these compounds are being increasingly detected in effluents of hospitals, influents and effluents of wastewater treatment plants, river surface water and sediments, groundwater, and even drinking water. Anticancer drugs can impact aquatic organisms such as algae, crustaceans, rotifers, and fish and may promote changes in soil and water microbial communities that may alter ecosystem functioning. Our knowledge of technologies for the removal of anticancer drugs is still limited, and these drugs can be dispersed in nature in a diffuse way in an uncontrolled manner. For this reason, an improved understanding of the presence, persistence, and ecological impacts of anticancer drugs in wastewater and natural environments is needed to help design management strategies, protect aquatic microorganisms, and mitigate potential ecological impacts.

Assessing the risks of capecitabine and its active metabolite 5-fluorouracil to freshwater biota

Capecitabine (CAP, prodrug) and 5-fluorouracil (5-FU, its active metabolite) are two of the most prominent cytostatics, for which no clear picture can be drawn regarding potential concentrations of effect for freshwater biota, with CAP being grouped in the least studied cytostatic, whereas 5-FU has been classified as of no and of high environmental risk. Accordingly, the present work aimed to assess the ecotoxicity of CAP and 5-FU in three freshwater species, which included a 72-h assay with the producer Raphidocelis subcapitata; a 96-h assay with the invertebrate secondary consumer Hydra viridissima; and a 96-h assay with embryos of the vertebrate secondary consumer Danio rerio. The following endpoints were monitored: yield and population growth rate for the algae; mortality, morphological alterations, and post-exposure feeding rates for the cnidarian; and mortality, hatching, and malformations for the fish. Overall, organisms' sensitivity to CAP decreased in the following order: R. subcapitata > H. viridissima > D. rerio, whereas for 5-FU, it decreased in the following order: H. viridissima > D. rerio > R. subcapitata. For CAP, no median lethal effective concentrations (LC/EC₅₀) were possible to compute for D. rerio, with no significant mortality or malformations registered in embryos exposed at concentrations up to 800 mg L^-1. For R. subcapitata, the EC₅₀s were 0.077 and 0.63 mg L^-1 for yield and growth rate, respectively, and for H. viridissima, the EC_50,30 min for feeding was 22.0 mg L^-1. For 5-FU, no EC_50s could be computed for R. subcapitata, whilst the EC_50s for H. viridissima mortality and feeding were 55.4 and 67.9 mg L^-1, respectively, and for D. rerio, the LC_50,96 h and EC_50,96 h (hatching and abnormalities) were 4546, 4100, and 2459 mg L^-1, respectively. Assuming similar modes of action for both compounds and their co-occurrence, the combined risk quotient of the two chemicals was determined to be 7.97, which represents a risk for freshwater biota. Anticipating the increased consumption of these compounds and cancer development trends worldwide, these impacts may be further aggravated.

Origin, transport and ecological risk assessment of illicit drugs in the environment - A review

Illicit drugs are a novel group of emerging pollutants. A growing global environmental load and ecological risk is created by the ongoing release of these toxins into the environment. Conventional water processing plants fail to completely remove drugs of abuse from both surface water and wastewater. The origin, environmental fate and ecological repercussions of illicit drugs, despite their detection in surface waterways around the world, are not well understood. In this review, illicit drug detections in potable water, surface water and wastewater globally have been studied during the past 15 years in order to establish a baseline for future years. The most common drugs with abuse potential detected in different sources of potable and surface water were methadone (0.12-22.7 ng/L), cocaine (0.05-506.6 ng/L), benzoylecgonine (0.07-1019 ng/L), amphetamine (1.4-342.6 ng/L), and codeine (0.002-42 ng/L). The bulk of research only looked at a small number of drugs of abuse, indicating that despite widespread use, a large spectrum of these intoxicants has yet to be detected. This review focuses on the origin of illicit drug contaminants in water bodies, air, and soil, their persistence in the environment, and the typical concentrations at which they occur in the environment. The impact of these drugs on aquatic organisms like Elliptio complanata mussels, crayfish and zebrafish has also been reviewed.

Assessing the effects of the cytostatic drug 5-Fluorouracil alone and in a mixture of emerging contaminants on the mussel Mytilus galloprovincialis

The assessment of contaminants of emerging concern, alone and in mixtures, and their effects on marine biota requires attention. 5-Fluorouracil is a cytostatic category 3 anti-cancer medication (IARC) that is used to treat a variety of cancers, including colon, pancreatic, and breast cancer. In the presence of other pollutants, this pharmaceutical can interact and form mixtures of contaminants, such as adhering to plastics and interaction with metal nanoparticles. This study aimed to comprehend the effects of 5-Fluorouracil (5FU; 10 ng/L) and a mixture of emerging contaminants (Mix): silver nanoparticles (nAg; 20 nm; 10 μg/L), polystyrene nanoparticles (nPS; 50 nm; 10 μg/L) and 5FU (10 ng/L), in an in vivo (21 days) exposure of the mussel Mytilus galloprovincialis. A multibiomarker approach namely genotoxicity, the antioxidant defence system (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidases (GPx), glutathione - S - transferases (GST) activities), and oxidative damage (LPO) was used to assess the effects in gills and digestive gland of mussels. Both treatments cause genotoxicity in mussel's haemolymph, and antagonism between contaminants was observed in the Mix. Genotoxicity observed confirms 5FU's mode of action (MoA) by DNA damage. The antioxidant defence system of mussels exposed to 5FU kicked in and counter balanced ROS generated during the exposure, though the same was not seen in Mix-exposed mussels. Mussels were able to withstand the effects of the single compound but not the effects of the Mix. For oxidative stress and damage, the interactions of the components of the mixture have a synergistic effect.

Enhanced MnO2 oxidation of methotrexate through self-sensitized photolysis

MnO₂, which is ubiquitous in soil and sediment in natural water environments, may play an important role in the photolysis of contaminants by sunlight, but the interactions between MnO₂ and contaminants in aqueous environments under sunlight irradiation have not been investigated. In this study, the simultaneous presence of sunlight and MnO₂ significantly enhanced the degradation efficiency of methotrexate (MTX). Accordingly, we hypothesized that the overall enhancement of this synergistic reaction is due to the additional production of Mn(III) via MTX self-sensitized photolysis. The pseudo-first-order kinetic model for the photoreaction of MTX with MnO₂ (Light/MTX+MnO₂) during the initial reaction kinetics (0-2 h) revealed a rate constant of 0.43 h¹ ([MTX] = 20 μM, [MnO₂] = 200 μM, and pH = 7), which is faster than that obtained with sunlight alone (0.14 h¹) or MnO₂ alone; Mn(II) and Mn(III) were formed at concentrations of 24.3 ± 1.0 μM and 14.8 ± 1.4 μM, respectively. Dissolved Mn(III) species were identified as the main oxidant species responsible for the degradation of MTX. Two reaction pathways for the production of Mn(III) through Light/MTX+MnO₂ were proposed; MTX acts as a photosensitizer to produce ³MTX* responsible for the reduction of MnO₂ to Mn(III), whereas O₂^• participates in the oxidation of Mn(Ⅱ) to Mn(Ⅲ). Byproduct analysis demonstrated that the Mn(III) generated in the Light/MTX+MnO₂ system enhances C－N bond cleavage, ketonization, and hydrolysis pathways in the MTX transformation.

Impact of 5-fluorouracil on anaerobic digestion using sewage sludge

The role of bacterial interaction is vital to control bacterial functions; however, it has not been fully understood in microbial consortia (including anaerobic digestion). In this study, fluorouracil (FU), which is an anticancer agent and a quorum sensing (QS) inhibitor to some of the Gram-negative bacteria was found to inhibit methane production from sewage sludge under anaerobic conditions, as shown in a result where methane production in the presence of FU was eight times lower than the control (sewage sludge without FU). Whereas FU did not influence the hydrolysis process, in the acidogenesis/acetogenesis process, butyrate, and acetate accumulated in samples with FU. Also, in the methanogenesis process, FU remarkably inhibited methane production by acetoclastic methanogens rather than by the hydrogenotrophic ones. This result agreed with the result that growth and methane production of Methanosarcina acetivorans C2A was inhibited in the presence of FU. However, the inhibitory effect of FU was high in the condition that both bacteria and archaea were active. It indicates that FU influences methanogens and bacteria in the process of methane fermentation. The analyses of microbial communities (bacteria and archaea) showed that the abundance ratio of the Firmicutes phyla is high, and hydrogenotrophic methanogens become dominant in the presence of FU. Conversely, the abundance of Spirochaetes significantly decreased under FU. The inhibition of methane production by FU was due to the growth inhibition of methanogenic archaea and the changes in the composition of the bacterial population.

Source, fate, transport and modelling of selected emerging contaminants in the aquatic environment: Current status and future perspectives

The occurrence of emerging contaminants (ECs), such as pharmaceuticals and personal care products (PPCPs), perfluoroalkyl and polyfluoroalkyl substances (PFASs) and endocrine-disrupting chemicals (EDCs) in aquatic environments represent a major threat to water resources due to their potential risks to the ecosystem and humans even at trace levels. Mathematical modelling can be a useful tool as a comprehensive approach to study their fate and transport in natural waters. However, modelling studies of the occurrence, fate and transport of ECs in aquatic environments have generally received far less attention than the more widespread field and laboratory studies. In this study, we reviewed the current status of modelling ECs based on selected representative ECs, including their sources, fate and various mechanisms as well as their interactions with the surrounding environments in aquatic ecosystems, and explore future development and perspectives in this area. Most importantly, the principles, mathematical derivations, ongoing development and applications of various ECs models in different geographical regions are critically reviewed and discussed. The recommendations for improving data quality, monitoring planning, model development and applications were also suggested. The outcomes of this review can lay down a future framework in developing a comprehensive ECs modelling approach to help researchers and policymakers effectively manage water resources impacted by rising levels of ECs.

Trends in Fenton and photo-Fenton processes for degradation of antineoplastic agents in water matrices: current knowledge and future challenges evaluation using a bibliometric and systematic analysis

Antineoplastic agents present potential hazards to human health and the environment. For this reason, these compounds have attracted a great deal of attention from researchers in the environmental sciences field. In order to help guide future research, it is important to understand the current state of investigation of the occurrence of these microcontaminants and methods for their removal, especially focusing on Fenton and photo-Fenton processes applied to various aqueous matrices in which this class of pharmaceuticals is present. For this purpose, a systematic review of these topics was performed by bibliometric analysis of articles published during the last decade and available in the Scopus and Web of Science databases. This study enables visualization of the current panorama and trends in this field, providing a guide for future collaborative research and exchange of knowledge. Various strategies have been suggested to improve the efficiency of Fenton and photo-Fenton processes, mainly by means of the application of multiples additions of iron, the use of heterogeneous catalysts, and/or the use of chelating agents. Some studies have evaluated different radiation sources employed for photo-Fenton processes, such as solar and/or artificial radiation. In turn, the identification of transformation products generated by Fenton and photo-Fenton treatments, together with their evaluation by in silico (Q)SAR predictions or experimental toxicological bioassays, are related subjects that have been less reported in published works and that should be studied in depth. These subjects can support treatment evaluations that are more realistic, considering their limitations or potentials.

Photoaged polystyrene microplastics serve as photosensitizers that enhance cimetidine photolysis in an aqueous environment

Microplastics (MPs) have received much attention in recent years because of their continuous photoaging process in aquatic environments. However, little research has been conducted on the photochemistry of aged microplastics and the associated effects on coexisting pharmaceuticals. This study investigated the photodegradation of cimetidine via aged polystyrene microplastics (PS-MPs) with different aging times (0-7 d) under simulated sunlight irradiation (700 W/m²). PS-MPs with 5 d of aging time resulted in much faster cimetidine degradation (>99%) after 2 h of irradiation than pristine PS-MPs (<8%). The enhanced photodegradation of cimetidine by aged PS-MPs was related to the increase in chromophoric oxygenated groups (CO, C-O) followed by redshifted absorbance through the photoaging process, which induced the formation of the environmentally persistent free radicals (EPFRs) OH, ¹O₂ and ³PS*. However, only ¹O₂ and ³PS* contributed to enhanced cimetidine photodegradation, with ¹O₂ playing a more important role in our case. This work also demonstrated that other compounds that are susceptible to indirect photolysis, such as codeine and morphine, are likewise significantly degraded under irradiation in the presence of aged PS-MPs. Although previous studies have reported how MPs can increase the persistence of contaminants, this study demonstrates that MPs can serve as photosensitizers and alter the fate of coexisting pharmaceuticals in aquatic environments.

The effects of the chemotherapy drug cyclophosphamide on the structure and functioning of freshwater communities under sub-tropical conditions: A mesocosm study

Cyclophosphamide (CP) is a chemotherapy drug which is widely used in the treatment of neoplastic diseases and have often been detected in urban and hospital wastewater, and surface waters. However, at present the effects of CP on aquatic organisms and ecosystems are poorly understood. The main objective of the present study was to assess the effect of CP on the structure and functioning of a sub-tropical freshwater ecosystem (macroinvertebrates, zooplankton and phytoplankton) at environmental relevant concentrations. CP (0, 0.5, 5 and 50 μg/L) was applied weekly to 13,600 L mesocosms over a period of four weeks followed by a one month post exposure period. CP was found to dissipate much faster than previous reported in literature and the half-dissipation times were treatment dependent, being 2.2, 21.3 and 23.6 days in the lowest, middle and highest treatments respectively. Only treatment related effects were observed on the community structure at individual samplings with zooplankton (NOEC_community = 0.5 μg/L) responding at lower concentrations than phytoplankton (NOEC_community = 5 μg/L) and macroinvertebrates (NOEC_community ≥ 50 μg/L). The dissolved organic carbon concentration was consistently higher in the 2 highest treatments, indicating a potential effect on food web interactions and/or the microbial loop. At the population level, consistent adverse effects were observed for the plankton taxa Pleuroxus laevis, Dissotrocha sp. and Oscillatoria sp. at all CP concentrations (NOEC <0.5 μg/L). Additionally, at the highest CP treatments 7% of all the taxa showed a clear short-term adverse effect. Based on comparison with literature data it can be concluded that these taxa have the highest CP sensitivity ever recorded and these findings indicate a potential CP risk to aquatic ecosystems at environmental relevant concentrations.

Photodegradation of methotrexate in aqueous solution: degradation kinetics and identification of transformation products

Methotrexate is an antineoplastic folate analog of high environmental concern, due to its low biodegradability and toxicological properties. This study focused on its photodegradation under two irradiation conditions, aiming to be representative of environment (300-450 nm) and drinking water treatment (254 nm). The photodegradation experiments were conducted at two pH, to vary the methotrexate ionization state and to produce a large variety of transformation products (TPs). The degradation kinetics determined through LC-UV monitoring were contrasted according to pH and irradiation wavelength. However, the quantum yields were independent of ionization state at 254 nm and the changes in kinetics at higher wavelengths were attributed to a change in the degradation mechanism. The TPs formed during the reactions were identified by UHPLC-MS/MS, using both the positive and negative modes. Among the eleven proposed structures, five were described as methotrexate TPs for the first time. The TPs result from N-demethylation, glutamic acid oxidation, and C-N cleavage, all of them leading to further degraded photoproducts presenting modified or lost glutamic acid part. This was made possible thanks to the negative mode, which allowed the exploration of the glutamic acid moiety modifications. Cytotoxicity assessment on A549 cancer cells demonstrated that all photoproducts formed at pH 7 were less toxic than the parent compound.

Treatment-driven removal efficiency, product formation, and toxicity evolution of antineoplastic agents: Current status and implications for water safety assessment

Antineoplastic compounds, designed for chemotherapeutic anticancer therapy, have become emerging contaminants of global concern over the past decade due to their ubiquitous occurrence, environmental persistence, and multiple adverse effects on aquatic ecosystems. Increasing efforts have been devoted to developing efficient strategies for remediating water containing these micropollutants. In this study, the physicochemical properties, natural attenuation, and chemical reactivity with aqueous oxidizing species of five antineoplastic drugs with the highest environmental prevalence (i.e., tamoxifen, cyclophosphamide, ifosfamide, 5-fluorouracil, and methotrexate) were summarized. The removal performance, transformation products (TPs) of varying structures, overall reaction pathways, and toxicity evolution during different treatments were evaluated and discussed. Additionally, the biodegradability and multi-endpoint toxicity of each TP were predicted using in silico QSAR software. Depending on their distinct inherent structures, the reactivity of the antineoplastics with oxidizing species varied, with hydroxyl radicals exhibiting unparalleled merits in rapid oxidation. Complete elimination of these contaminants was observed during oxidative treatments, but with inadequate mineralization. Notably, the increase in toxicity within multiple processes was determined based on both experimental bioassays and theoretical predictions. This may be attributed to the adverse effects induced by the large number of identified and unknown TPs individually and in combination. Together with the environmental persistence and low biodegradability of most TPs, these results necessitate the application of efficient post-treatments in conjunction with a more thorough water safety evaluation (e.g., using high-throughput screening) of the mixtures of treated water and wastewater.

Spatial distribution of pharmaceuticals within the particulate phases of a peri-urban stream

Pharmaceutical products (PPs) are consumed worldwide and are continuously released into hydrological environments, but are not efficiently removed by sewage treatment plants. Their occurrence within the dissolved phase has been extensively studied, but only a few articles concern solid matrices. The mechanisms and extent of sorption depend on the properties of both the molecules (degradability, charge, hydrophobicity) and the matrices (clay content, organic matter content), making the spatio-temporal distribution of PPs in natural environments complex and poorly elucidated. To improve our understanding of PP distribution at a catchment scale, this study investigated different groups of molecules with varying solubility and charges, in water, suspended particulate matter, bed-load and pond sediments. The Egoutier stream, which collects the sewage effluents from two health institutions sewage effluents, is a good candidate for this investigation. Results indicate that PP occurrences in the different particulate compartments were mainly regulated by their wastewater occurrences and charges. Particulate phases all along the Egoutier stream were characterized by a limited clay content (i.e. less than 1%) and significant organic carbon content (i.e. between 0.3% and 18.0%) favouring non-specific adsorption. Therefore, neutral PPs, exhibiting higher discharge rates, persistence and hydrophobicities in comparison with cationic and anionic molecules, were the most abundant PPs in the particulate phases of this catchment. In bed-load sediments, global PP spatial distributions reflected discharge sites and sedimentary accumulation zones, mostly that of organic matter. Spatial distributions of the more hydrophobic and persistent PP in the particulate phases thus followed the stream sedimentary dynamic.

Occurrence, bioaccumulation and toxicological effect of drugs of abuse in aquatic ecosystem: A review

Drugs of abuse are a group of emerging contaminants. As the prevalence of manufacture and consumption, there is a growing global environmental burden and ecological risk from the continuous release of these contaminants into environment. The widespread occurrence of drugs of abuse in waste wasters and surface waters is due to the incomplete removal through traditional wastewater treatment plants in different regions around the world. Although their environmental concentrations are not very high, they can potentially influence the aquatic organisms and ecosystem function. This paper reviews the occurrence of drugs of abuse and their metabolites in waste waters and surface waters, their bioaccumulation in aquatic plants, fishes and benthic organisms and even top predators, and the toxicological effects such as genotoxic effect, cytotoxic effect and even behavioral effect on aquatic organisms. In summary, drugs of abuse occur widely in aquatic environment, and may exert adverse impact on aquatic organisms at molecular, cellular or individual level, and even on aquatic ecosystem. It necessitates the monitoring and risk assessment of these compounds on diverse aquatic organisms in the further study.

Anticancer drugs in the aquatic ecosystem: Environmental occurrence, ecotoxicological effect and risk assessment

Anticancer drugs are a group of therapeutic agents used to enhance cell death in targeted cell types of neoplasia. Because of frequent use and eventual discharge, they have been often detected in wastewater from pharmaceutical factories and hospitals, domestic wastewater, and surface waters. The occurrence of these drugs in aquatic ecosystems and their effects on aquatic organisms have been poorly characterized. This review focuses on the global occurrence of major classes of anticancer drugs in water and sediments of freshwater ecosystems and their ecotoxicological effects at different biological levels. While the availability of data is fairly limited, concentrations of most anticancer drugs range from < 2 ng/L to 762 µg/L in receiving water, while levels in sediments and sludge vary from 0.25 to 42.5 µg/kg. Their detection frequencies were 58%, 52% (78%) and 59% in hospital wastewater, wastewater treatment plant effluents (influents) and surface water, respectively. Predicted log K_ow values of vincristine, imatinib mesylate and tamoxifen are higher than 3 and have estimated half-lives>60 d in waters using quantitative structure-activity relationship models, indicating high potential for persistence and bioaccumulation. Based on a species sensitivity distribution evaluation of 9 compounds, crustaceans are most sensitive to anticancer drugs. The most hazardous compound is cisplatin which has a hazard concentration at the 5th percentile. For Daphnia magna, the acute toxicities of major classes of anticancer drugs are ranked as platinum complexes > endocrine therapy agents > antibiotics > antimetabolite agents > alkylating agents. Using hazard quotient analysis based primarily on the lowest observed effect concentrations (LOECs), cyclophosphamide, cisplatin, 5-fluorouracil, imatinib mesylate, bicalutamide, etoposide and paclitaxel have the highest hazard for aquatic organisms. Further research is needed to identify appropriate chronic endpoints for risk assessment thresholds as well as to better understand the mechanisms of action and the potential multigenerational toxicity, and trophic transfer in ecosystems.

Assessment on chronic and transgenerational toxicity of methamphetamine to Caenorhabditis elegans and associated aquatic risk through toxicity indicator sensitivity distribution (TISD) analysis

Evidence about the adverse effects of methamphetamine (METH) on invertebrates is scarce. Hence, C. elegans, a representative invertebrate model, was exposed to METH at environmental levels to estimate chronic and transgenerational toxicity. The results of chronic exposure were integrated into an underlying toxicity framework of METH in invertebrates (e.g., benthos) at environmentally relevant concentrations. The induction of cellular oxidative damage-induced apoptosis and fluctuation of ecologically important traits (i.e., feeding and locomotion) might be attributed by the activation of the longevity regulating pathway regulated by DAF-16/FOXO, and detoxification by CYP family enzymes. The adverse effects to the organism level included impaired viability and decreased fecundity. The results from transgenerational exposure elucidated the cumulative METH-induced damage in invertebrates. Finally, a new risk assessment method named toxicity indicator sensitivity distribution (TISD) analysis was proposed by combining multiple toxicity indicator test data (EC_x) to derive the hazardous concentration for 10% indicators (C₁₀) of one species. The risk quotient (RQ) values calculated by measured environmental concentrations and C₁₀ in southern China, southeastern Australia, and the western US crossed the alarm line (RQ = 5), suggesting a need for long-term monitoring.

Intracellular organic matter from Chlorella vulgaris enhances the photodegradation of acetaminophen

Algae is able to accelerate the photodegradation rate of contaminants under sunlight irradiation, and this process can be attributed to algal substances, namely, intracellular organic matter (IOM) and extracellular organic matter (EOM). This study aimed to investigate the efficiencies and mechanisms of the photodegradation of three pharmaceuticals - acetaminophen (ACE), codeine (COD) and cephradine (CFD) - in the presence of Chlorella vulgaris and its algal substances. The result shows that a much higher photodegradation rate of acetaminophen was obtained in the presence of IOM (k_obs = 0.250 hr^-1) than in the presence of EOM (k_obs = 0.060 hr^-1). The photodegradation mechanisms of acetaminophen were demonstrated and verified by scavenger experiments and probe tests. The major reactive species for acetaminophen photodegradation was triplet-state IOM (³IOM∗), which contributed 93.52% of the photodegradation, while ⋅OH was the secondary contributor (5.60%), with ¹O₂ contributing the least (0.88%). Chlorella vulgaris also effectively enhanced the photodegradation of codeine and cephradine. However, the photodegradation behaviors of codeine and cephradine in the presence of algal substances were different from those of acetaminophen, indicating that the photodegradation mechanisms might depend on the type of compound. This study not only demonstrates the effectiveness of algal substances in the photodegradation of acetaminophen, codeine and cephradine under sunlight irradiation but also provides a comprehensive study on the photodegradation mechanisms of acetaminophen in the presence of algal substances.

Fate of N-nitrosodimethylamine and its precursors during a wastewater reuse trial in the Llobregat River (Spain)

In summer 2019, a full-scale trial was carried out to investigate the effects in drinking water quality when tertiary treated wastewater was discharged into the Llobregat River upstream of the intake of one of the major drinking water treatment plants of Barcelona and its metropolitan area. Two scenarios were investigated, i.e. discharging the reclaimed water with and without chemical disinfection with chlorine. This study investigates the concentration of N-nitrosodimethylamine (NDMA) as the specific disinfection conditions employed in this trial may favor its formation. To this aim, both NDMA and NDMA formation potential, were measured. The river contained NDMA at very low concentrations, but the concentration of NDMA precursors was already high. The NDMA concentration was reduced from discharge to the river to drinking water intake probably due to a combined effect of dilution and photolysis. The formation potential was also reduced probably due to dilution and biodegradation. The concentration of NDMA in the drinking water was always low (<7.3 ng/L), although the formation potential was above 10 ng/L in one sample. Dissolved organic matter characterization by high resolution mass spectrometry revealed differences between the nature of the organic matter in the river before and after reclaimed water discharge.

Insight into the Sorption of 5-Fluorouracil and Methotrexate onto Soil-pH, Ionic Strength, and Co-Contaminant Influence

Nowadays anticancer drugs (ADs), like other pharmaceuticals, are recognized as new emerging pollutants, meaning that they are not commonly monitored in the environment; however, they have great potential to enter the environment and cause adverse effects there. The current scientific literature highlights the problem of their presence in the aquatic environment by publishing more and more results on their analytics and ecotoxicological evaluation. In order to properly assess the risk associated with the presence of ADs in the environment, it is also necessary to investigate the processes that are important in understanding the environmental fate of these compounds. However, the state of knowledge on mobility of ADs in the environment is still very limited. Therefore, the main aim of our study was to investigate the sorption potential of two anticancer drugs, 5-fluorouracil (5-FU) and methotrexate (MTX), onto different soils. Special attention was paid to the determination of the influence of pH and ionic strength as well as presence of co-contaminants (cadmium (Cd²⁺) and another pharmaceutical-metoprolol (MET)) on the sorption of 5-FU and MTX onto soil. The obtained distribution coefficient values (K_d) ranged from 2.52 to 6.36 L·kg^-1 and from 6.79 to 12.94 L·kg^-1 for 5-FU and MTX, respectively. Investigated compounds may be classified as slightly or low mobile in the soil matrix (depending on soil). 5-FU may be recognized as more mobile in comparison to MET. It was proved that presence of other soil contaminants may strongly influence their mobility in soil structures. The investigated co-contaminant (MET) caused around 25-fold increased sorption of 5-FU, whereas diminished sorption of MTX. Moreover, the influence of environmental conditions such as pH and ionic strength on their sorption has been clearly demonstrated.

Vincristine exposure impairs skin keratinocytes, ionocytes, and lateral-line hair cells in developing zebrafish embryos

Environmental contamination by anticancer pharmaceuticals has been widely reported. These drugs are not readily biodegradable, and their parent compounds and/or metabolites have been detected in surface waters and groundwater throughout the world. Adverse effects of anticancer drugs occur frequently in cancer patients, and a large body of clinical knowledge has accumulated. However, the effects of these drugs on aquatic organisms have not been thoroughly studied. This study aimed to investigate the effects of acute exposure to a common anticancer drug, vincristine (VCR), on zebrafish embryonic development and skin function. After 96 h of VCR exposure (0, 1, 10, 15, and 25 mg/L), significant teratogenic effects were observed, including growth retardation, pericardial edema, spine, tail, and yolk sac malformations (VCR ≥ 15 mg/L), a decreased heart rate, and ocular malformations (VCR ≥ 10 mg/L). The value of the half lethal concentration for zebrafish embryos was 20.6 mg/L. At ≥10 mg/L VCR, systemic ion contents and acid secretion in the skin over the yolk-sac decreased, and these findings were associated with decreases in skin ionocytes (H⁺-ATPase-rich cells and Na⁺-K⁺-ATPase-rich cells). Also, the microridge-structure of skin keratinocytes was significantly damaged. The number of lateral line hair cells was reduced when VCR was ≥10 mg/L, and functional impairment was detected when VCR was as low as 1 mg/L. Results of this in vivo study in zebrafish embryos indicate that acute exposure to VCR can lead to developmental defects, impairment of skin functions, and even fish death.

Diluted concentrations of methamphetamine in surface water induce behavior disorder, transgenerational toxicity, and ecosystem-level consequences of fish

Methamphetamine (METH) has been recognized as an emerging organic contaminant as it was widely detected in the aquatic environment via wastewater effluent discharge. However, the ecological hazard posed by METH at environmentally relevant concentrations was remained unclear. In this study, adult medaka fish were exposed to METH at environmental levels (0.05, 0.2, 0.5, 5 μg L^-1) and high level (25 and 100 μg L^-1) for 90 days to investigate its effect on ecologically behavioral functions, histopathology, bioconcentration, and transgenerational toxicity. The significant increase of locomotion activity, total distance, and max velocity of adult medaka were observed at low METH levels (0.2-0.5 μg L^-1), while it markedly decreased at high levels (25-100 μg L^-1). This effect may increase the predation risk of the fish. The significant alteration on the relative expressions of the genes (cacna1c, oxtr, erk1, and c-fos), as well as the contents of the proteins (oxytocin (OXT) and protein kinase A (PKA)) involved in Voltage Dependent Calcium Channel (VDCC) and Mitogen-Activated Protein Kinase (MAPK) signaling channel induced by METH could partly elucidate the underlying mechanisms of the changes of the behavioral traits. METH could induce obvious minimal gliosis, neuronal loss, and necrotic in brain tissues. Additionally, the significant increase of hepatic-somatic index (HSI) of male medaka at 0.2-5 μg L^-1 groups, and the decrease of female medaka at 100 μg L^-1 group indicated male fish was more susceptible to METH. Nephric-somatic index (NSI) of medaka markedly declined induced by METH at 0.05-100 μg L^-1. The bioconcentration factor (BCF) (0.4-5.8) in medaka fish revealed the bioconcentration potential of METH in fish. This study for the first time demonstrated METH could induced the development defects of larvae in F1 generation at environmentally relevant concentrations, thereby resulting in a significant decrease in the capacity of fish to produce offspring. Meanwhile, the RQ values (>1) of METH in river in China, USA, and Australia showed a high teratogenic risk level, suggesting the ecosystem-levels consequence posed by METH should be concerned.

Determination of dextromethorphan and dextrorphan solar photo-transformation products by LC/Q-TOF-MS: Laboratory scale experiments and real water samples analysis

This work discusses the identification of the transformation products (TPs) generated during the photolytic degradation of dextromethorphan (DXM) and its metabolite dextrorphan (DXO), under simulated solar radiation in aqueous solutions (Milli-Q water and river water) in order to determinate its behavior into the aquatic environment. Tentative identification of the TPs was performed by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS), following a suspect screening approach. The use of high resolution-mass spectrometry (HRMS) allowed the tentative identification of DXM and DXO photoproducts based on the structure proposed by an in silico software, the accurate mass measurement, the MS/MS fragmentation pattern and the molecular formula finding. A total of 19 TPs were found to match some of the accurate masses included in a suspect list, and they were all tentatively identified by their characteristic MS-MS fragments. Most of the TPs identified showed a minor modified molecular structure like the introduction of hydroxyl groups, or demethylation. The time-evolution of precursors and TPs were monitored throughout the experiments, and degradation kinetics were presented for each analyte. Finally, the occurrence of DXM, DXO, and their tentatively proposed photodegradation TPs was evaluated in both surface and wastewater. In all real matrices, the results showed that the highest concentration was detected for DXO, followed by TP-244 (N-desmethyldextrorphan) and DXM.

Evaluation of pharmaceutical abuse and illicit drug use in South Korea by wastewater-based epidemiology

Drug abuse trends in South Korea were assessed by estimating the consumption rates of drugs that may be abused or misused by performing wastewater-based drug epidemiology. Of the 29 target compounds, 10 were found in samples from three wastewater treatment plants. Ephedrine had the highest mean estimated consumption rate, 574.1 mg d^-1 (1000 people)^-1. The anti-obesity drugs phendimetrazine and phentermine had the second and fifth highest mean estimated consumption rates, 182.9 and 113.1 mg d^-1 (1000 people)^-1, respectively. The zolpidem consumption rate was 65.8 mg d^-1 (1000 people)^-1. Methamphetamine was the only illicit drug detected in wastewater, and the estimated consumption rates (14.9-28.6 mg d^-1 (1000 people)^-1) were similar to consumption rates found in previous Korean studies (not detected to 45.8 mg d^-1 (1000 people)^-1). The mean estimated meperidine and cis-tramadol (opioid) consumption rates were 120 and 27.5 mg d^-1 (1000 people)^-1, respectively, and were 8.2 and 1.7 times higher, respectively, than the consumption rates found in 2013. Methylphenidate was detected in the influent and effluent samples at mean concentrations of 2.7 and 2.6 ng L^-1, respectively, but the methylphenidate consumption rate could not be estimated because of the low excretion rate for humans (<1%).

Review on the occurrence and biological effects of illicit drugs in aquatic ecosystems

Illicit drugs (IDs) and their metabolites are recognized as contaminants of emerging concern. After consumption, illicit drugs are partially metabolized and excreted unchanged in urine and feces or as active metabolites reaching wastewater treatment plants (WWTPs). Furthermore, most WWTPs are insufficient in the treatment of effluents containing IDs, which may be released into aquatic ecosystems. Once in the water or sediment, these substances may interact and affect non-target organisms and some evidences suggest that illicit drugs may exhibit pseudo-persistence because of a continuous environmental input, resulting in long-term exposure to aquatic organisms that may be negatively affected by these biologically active compounds. We reviewed the literature on origin and consumption, human metabolism after consumption, aquatic occurrences, and toxicity of the major groups of illicit drugs (opioids, cannabis, synthetic drugs, and cocaine). As a result, it could be concluded that illicit drugs and their metabolites are widespread in diverse aquatic ecosystems in levels able to trigger sublethal effects to non-target organisms, besides to concentrate in seafood. This class of emerging contaminants represents a new environmental concern to academics, managers, and policymakers, whose would be able to assess risks and identify proper responses to reduce environmental impacts.

Making 'Chemical Cocktails' - Evolution of Urban Geochemical Processes across the Periodic Table of Elements

Urbanization contributes to the formation of novel elemental combinations and signatures in terrestrial and aquatic watersheds, also known as 'chemical cocktails.' The composition of chemical cocktails evolves across space and time due to: (1) elevated concentrations from anthropogenic sources, (2) accelerated weathering and corrosion of the built environment, (3) increased drainage density and intensification of urban water conveyance systems, and (4) enhanced rates of geochemical transformations due to changes in temperature, ionic strength, pH, and redox potentials. Characterizing chemical cocktails and underlying geochemical processes is necessary for: (1) tracking pollution sources using complex chemical mixtures instead of individual elements or compounds; (2) developing new strategies for co-managing groups of contaminants; (3) identifying proxies for predicting transport of chemical mixtures using continuous sensor data; and (4) determining whether interactive effects of chemical cocktails produce ecosystem-scale impacts greater than the sum of individual chemical stressors. First, we discuss some unique urban geochemical processes which form chemical cocktails, such as urban soil formation, human-accelerated weathering, urban acidification-alkalinization, and freshwater salinization syndrome. Second, we review and synthesize global patterns in concentrations of major ions, carbon and nutrients, and trace elements in urban streams across different world regions and make comparisons with reference conditions. In addition to our global analysis, we highlight examples from some watersheds in the Baltimore-Washington DC region, which show increased transport of major ions, trace metals, and nutrients across streams draining a well-defined land-use gradient. Urbanization increased the concentrations of multiple major and trace elements in streams draining human-dominated watersheds compared to reference conditions. Chemical cocktails of major and trace elements were formed over diurnal cycles coinciding with changes in streamflow, dissolved oxygen, pH, and other variables measured by high-frequency sensors. Some chemical cocktails of major and trace elements were also significantly related to specific conductance (p<0.05), which can be measured by sensors. Concentrations of major and trace elements increased, peaked, or decreased longitudinally along streams as watershed urbanization increased, which is consistent with distinct shifts in chemical mixtures upstream and downstream of other major cities in the world. Our global analysis of urban streams shows that concentrations of multiple elements along the Periodic Table significantly increase when compared with reference conditions. Furthermore, similar biogeochemical patterns and processes can be grouped among distinct mixtures of elements of major ions, dissolved organic matter, nutrients, and trace elements as chemical cocktails. Chemical cocktails form in urban waters over diurnal cycles, decades, and throughout drainage basins. We conclude our global review and synthesis by proposing strategies for monitoring and managing chemical cocktails using source control, ecosystem restoration, and green infrastructure. We discuss future research directions applying the watershed chemical cocktail approach to diagnose and manage environmental problems. Ultimately, a chemical cocktail approach targeting sources, transport, and transformations of different and distinct elemental combinations is necessary to more holistically monitor and manage the emerging impacts of chemical mixtures in the world's fresh waters.

Using zebrafish to assess the effect of chronic, early developmental exposure to environmentally relevant concentrations of 5-fluorouracil and leucovorin

Environmental contaminants can deleteriously affect aquatic animals. One such contaminant is 5-fluorouracil (5-FU), a long-prescribed chemotherapeutic drug. Leucovorin (LV) is co-administered with 5-FU, potentiating its effects. Zebrafish (Danio rerio) larvae were reared in ng/L treatments of either 5-FU, LV, or a combined 5-FU/LV mixture for 8 dy. Survival was measured daily and swimming behavior assessed every other day. After 8 dy, larval length was measured, and densitometry of p53-labeled cryostat sections determined the extent of apoptosis. No significant differences in survival or apoptosis were found; larvae in the highest concentrations were largest. Changes in behavior of 5-FU-treated larvae were based on exposure duration; changes in LV-treated larvae were affected by drug concentration and duration. Larvae co-exposed to 5-FU/LV had responses like 5-FU-treated larvae. Overall, early developmental exposure of zebrafish larvae to environmentally-relevant concentrations of 5-FU and LV did not adversely affect survival, growth, and behavior suggesting realistic concentrations are sublethal and non-toxic.

Urban wastewater treatment plants as a potential source of ketamine and methamphetamine emissions to air

Urban wastewater treatment plants (WWTPs) can be an emission source of aerosol particles to the air and this process has the potential to spread emerging pollutants into the air, where the particles can be widely transported over long distances to areas where this pollution is unexpected. This study demonstrates aeration tanks in WWTPs as a potential source of ketamine, methamphetamine and other emerging contaminant emissions into the air. Ketamine and methamphetamine are frequently detected in high concentrations (maximum of 151.8-162.8 pg/m³) in gaseous and aerosol samples along with 24 other emerging contaminants. Through correlation analysis, the common occurrence of emerging contaminants in air is attributable to their high aqueous concentrations as well as their physicochemical properties. Two simple regression models are developed to provide a practical and convenient way to estimate the steady-state concentrations in air. The gas-phase emission model illustrates the relationship between the solubility, the pK_a and the aqueous concentration of compounds in the aeration basin and their gaseous concentrations in air (statistical strength of 74.1%; p value < 0.05), while the partition model establishes the ratio of a compound in the gas and particulate phases in air (statistical strength of 82.6%; p value < 0.05). The results provide a basis for assessing the risk of the inhalation exposure to airborne emerging contaminants; however, in-depth research addressing the impact of aerosols containing persistent pharmaceuticals on human health is still needed.

Effect of Floodplain Restoration on Photolytic Removal of Pharmaceuticals

Floodplain restoration is popular to address excess nutrients, but its ability to enhance photolysis of emerging contaminants has not been evaluated. We used the numerical model MIKE-21 to simulate photolysis reactions within the inundated surface water of restored floodplains along a mid-size river. We examined both "high" and "low" floodplain scenarios where inundation occurs 5% (storms) and 50% (baseflow) of the year, respectively. We simulated photolysis of the pharmaceuticals morphine, codeine, and methamphetamine and, for context, compared it with nitrate removal (denitrification and plant uptake). Pollutant removal due to floodplain restoration was greater for the low floodplain (e.g., 18.8% for morphine) than for the high floodplain (5.6% for morphine) due to greater water exchange relative to channel flow. The fastest- and slowest-reacting pollutants (morphine and methamphetamine, respectively) were always transport- and reaction/kinetics-limited within floodplain surface water, respectively. Yet, those with intermediate decay-rate constants switched from reaction limitation to transport limitation as the floodplain length increased, and removal leveled off at an optimum length of ∼1000 m. However, as the floodplain width increased, the required floodplain length for 30% removal decreased. Optimal restored floodplain conditions for photolysis would maximize light exposure, which may differ from those for nutrients.

Simultaneous degradation of the anticancer drugs 5-fluorouracil and cyclophosphamide using a heterogeneous photo-Fenton process based on copper-containing magnetites (Fe3-xCuxO4)

The effect of substitution of iron by copper in the magnetite lattice was investigated in terms of the catalytic activity in the heterogeneous photo-Fenton process. The physicochemical properties of the Fe_3-xCu_xO₄ nanoparticles were characterized by X-ray diffraction (XRD), X-ray fluorescence (WD-XRF), specific surface area measurements, field emission scanning electron microscopy (FEG-SEM), and X-ray photoelectron spectroscopy (XPS). Copper-modified magnetite showed higher catalytic activity for H₂O₂ conversion to HO^• (estimated using 7-hydroxycoumarin), compared to pristine magnetite (Fe₃O₄). Consequently, improved degradation of the anticancer drugs 5-fluorouracil (5-FU) and cyclophosphamide (CP) was observed, with high efficiencies achieved using Fe_2.75Cu_0.25O₄ (0.125 g L^-1) and 15 mmol L^-1 H₂O₂, at pH 6.5, which resulted in complete degradation of 7.7 μmol L^-1 5-FU and CP after 150 min. Low leaching of Cu and Fe demonstrated the stability of the catalyst in the Fenton process, with high catalytic activity (>90%) maintained after use in 4 cycles. The addition of radical scavengers such as methanol, tert-butanol and iodide ions indicated that surface-bonded hydroxyl radicals played a major role in the degradation of 5-FU and CP in the Fe_3-xCu_xO₄/H₂O₂ system. The substitution of octahedral Fe(II) sites of the magnetite lattice by Cu(II) and the partial oxidation of Cu(I) to Cu(II) and Fe(II) to Fe(III) on the catalyst surface after the Fenton reaction were confirmed by analysis of the XPS spectra.

Environmental risk assessment of widely used anticancer drugs (5-fluorouracil, cisplatin, etoposide, imatinib mesylate)

Anticancer drugs are among the most toxic chemicals, which are commercially produced; therefore, their release in aquatic ecosystems raised concerns in regard to potential adverse effects. This article describes the results of risk assessments concerning their environmental safety, which are based on data generated in the frame of a coordinated EU project ("Cytothreat"). Eight research institutions participated in the project and four widely used anticancer drugs with different mechanisms of therapeutic action (5-fluorouracil 5FU, cisplatin CDDP, imatinib mesylate IM and etoposide ET) were tested in a variety of indicator organisms (cyanobacteria, algae, higher plants, rotifers, crustacea, fish and also in human and fish derived cell lines) in acute/subacute/chronic toxicity assays. Furthermore, genotoxic effects in micronucleus assays, single cell gel electrophoresis experiments and γH2AX tests were studied in plants, crustacea, fish and in various cell lines. We used the results to calculate the predicted no effect concentrations (PNEC) and risk quotients (RQ) by comparing PNEC with predicted environmental concentrations (PEC values) and measured concentrations (MEC) in wastewaters. The most sensitive species in experiments concerning acute toxic and long term effects were in general crustacea (daphnids) after chronic treatment the most pronounced effects were detected with IM followed by CDDP and 5FU. Comparisons between PNEC and PEC values indicate that it is unlikely that the release of these drugs in the aquatic environments leads to adverse effects (RQ values < 1). However, when the assessments were performed with MEC found in highly contaminated municipal wastewaters and hospital effluents, RQ values were obtained which are indicative for moderate adverse effects of IM. Calculations with data from genotoxicity experiments and PEC values are indicative for increased RQ values for all compounds except ET. The most sensitive species were fish (Danio rerio) which were highly responsive towards 5FU and daphnids which were sensitive towards CDDP and IM. When environmental data (from waste waters) were used for the calculations, high RQ values (>100) were obtained for CDDP and IM. These overall conclusions were not substantially altered when the effects of other frequently used cytostatic drugs and combined effects of mixtures of anticancer drugs were taken into consideration. The results of these assessments underline the importance of efficient removal of these chemicals by improved sewage treatment strategies and the need for further investigations of adverse the long term effects of cytostatics in aquatic biota as a consequence of damage of the genetic material in highly sensitive species.

Prospects for finding Junge variability-lifetime relationships for micropollutants in the Danube river

Persistence of chemical pollutants is difficult to measure in the field. Junge variability-lifetime relationships, correlating the relative standard deviation of measured concentrations with residence time, have been used to estimate persistence of air pollutants. Junge relationships for micropollutants in rivers could provide evidence that half-lives of compounds estimated from laboratory and field data are representative of half-lives in a specific system, location and time. Here, we explore the hypothesis that Junge relationships could exist for micropollutants in the Danube river using: (1) concentrations of six hypothetical chemicals modeled using the STREAM-EU fate and transport model, and (2) concentrations of nine micropollutants measured in the third Joint Danube Survey (JDS3) combined with biodegradation half-lives reported in the literature. Using STREAM-EU, we found that spatial and temporal variability in modeled concentrations was inversely correlated with half-life for the four micropollutants with half-lives ≤90 days. For these four modeled micropollutants, we found Junge relationships with slopes significantly different from zero in the temporal variability of concentrations at 88% of the 67 JDS3 measurement sites, and in the spatial variability of concentrations on 36% out of 365 modeled days. A Junge relationship significant at the 95% confidence level was not found in the spatial variability of nine micropollutants measured in the JDS3, nor in STREAM-EU-modeled concentrations extracted for the dates and locations of the JDS3. Nevertheless, our model scenarios suggest that Junge relationships might be found in future measurements of spatial and temporal variability of micropollutants, especially in temporal variability of pollutants measured downstream in the Danube river.

Removal of emerging drugs of addiction by wastewater treatment and water recycling processes and impacts on effluent-associated environmental risk

Drugs of addiction, have been recognized as potential contaminants of concern to the environment. Effluent wastewater discharge is a major source of contamination to aquatic receiving environments. A year-long monitoring program was undertaken in Australia to characterise the fate of four emerging drugs of addiction: methamphetamine; MDMA; pharmaceutical opioids: codeine and morphine and a metabolite: benzoylecgonine in four wastewater treatment plants operating with different secondary treatment technologies: conventional activated sludge (CAS), membrane bioreactors (MBR), integrated fixed-film AS (IFAS) and sequencing batch reactor (SBR). The effect of subsequent tertiary treatment (coagulation/flocculation) on the removal efficiency was also assessed. Drugs were detected in influent and effluent samples (mean concentration ranged from 43-4777 and 17-1721 ng/L, respectively). Treated effluents had noticeably lower levels compared to raw influents. Removal efficiency of compounds depended on the secondary treatment employed, with IFAS and MBR performing the best with significant removal of compounds (≈90%) followed by CAS (54-96%) and lastly SBR (42-83%). Despite the low levels of drugs measured after the secondary treatment, near complete removal after tertiary treatment (≈99%) was recorded, which demonstrated the effectiveness of using the coagulation/flocculation process as an effective step for enhancing the removal efficiency. The levels of drugs were at a low level in the effluents released into the environment and used for recycling and all posed a low environmental risk in urban water courses based on the risk assessment. The information given here provides new and useful information to the water industry and regulators on the efficiency of drug removal in a range of wastewater treatment configurations.

Mechanism and pathways underlying the self-sensitized photodegradation of methotrexate under simulated solar irradiation

Methotrexate, a chemotherapeutic agent, was found to undergo self-sensitized photodegradation in aqueous environments. As the initial concentration increased, methotrexate was able to enhance its own direct photolysis reaction not only in DI but also in natural waters. The methotrexate degradation rate increased through the production of singlet oxygen (¹O₂), the triplet excited state of methotrexate (³MTX^*), and the triplet excited state of the pteridine structure (³PT^*) from the phototransformation byproducts. At low methotrexate concentrations (<20 ppb), ¹O₂ played an important role, whereas at higher methotrexate concentrations (>2000 ppb), the presence of oxygen decreased the overall methotrexate degradation rate by physically quenching ³MTX^* and ³PT^*. The cleavage of the CN bond resulted in a significant amount of byproducts: pteridine derivatives and N-(4-aminobenzoyl)-l-glutamic acid (yields: 13.5 ± 0.6% and 32.3 ± 2.2% for 10 ppm and 500 ppb MTX, respectively). The reactivity of the phototransformation byproducts and the substructures of methotrexate were investigated to help elucidate the proposed self-sensitized pathways. The results indicated that methotrexate as well as compounds containing a pteridine structure will generate pteridine byproducts during photodegradation and ³PT^* is the primary triplet excited species that can cause self-sensitized photodegradation.

Ecotoxicity risk of presence of two cytostatic drugs: Bleomycin and vincristine and their binary mixture in aquatic environment

Cytostatic drugs have become one of the greatest environmental threats. They occur in surface, ground and even drinking water. Their key emission sources are hospital effluents, municipal wastewater, as well as drug manufacturers and their effluents. These compounds are extremely stable in natural waters and they are not significantly removed during wastewater treatment, because they are resistant to biodegradation. The aim of this work was to establish possible negative effects of chosen cytostatics: bleomycin and vincristine on the three trophic levels of surface waters. A single agent acute toxicity test was conducted on representatives of the producer - an aquatic freshwater plant Lemna minor, the consumer - crustaceans Daphnia magna, and the decomposer - bacteria Pseudomonas putida. Binary mixture tests were performed according to the Concentration Addition, Response Additivity, and Independent Action models. Both substances had a different effect on the tested organisms; bleomycin could be classified as a very toxic, while vincristine as a toxic water pollutant. Half maximal effective concentration (EC50) values designed in the presented single agent acute toxicity studies are < 10 mg/L in all the tests with bleomycin as well as vincristine conducted on L. minor. In tests with vincristine performed on D. magna and P. putida EC50 > 100 mg/L. The highest toxicity is demonstrated by bleomycin towards the aquatic freshwater plant (EC50 = 0.2 mg/L). The binary mixture of the tested chemicals showed antagonistic effects of environmental concern.

Cisplatin exposure impairs ionocytes and hair cells in the skin of zebrafish embryos

This study aimed to assess the sublethal effects of a platinum-based compound, cisplatin, using a zebrafish model. Zebrafish embryos were incubated in different concentrations of cisplatin at 0-96 h post-fertilization. Using a non-invasive, scanning ion-selective electrode technique (SIET), we measured the functions of hair cells (Ca²⁺ influx) and ionocytes ([H⁺] gradients). The survival rate, hatching rate, phenotype, body length, whole-body ion (Na⁺, Cl^-, and Ca²⁺) and Pt contents were also determined. The effects of cisplatin on zebrafish embryos were demonstrated as first impairing hair cell function (at 1 μM of cisplatin), the hair cell number, and body ion content of Cl^- (at 10 μM of cisplatin), then decreasing ionocyte acid secretion and overall body ion contents of Na⁺ and Ca²⁺ (at 50 μM of cisplatin). The body length and ionocyte density decreased at 100 μM of cisplatin, and survival decreased at 500 μM of cisplatin. As the cisplatin concentration increased, the accumulation of Pt in fish embryos also increased. These results revealed that hair cells are significantly more susceptible to cisplatin toxicity than ionocytes. By determining the lowest observed effective concentration of cisplatin that caused in vivo functional alterations of zebrafish hair cells and skin ionocytes, this model demonstrated 500-fold greater sensitivity than by detecting changes in survival, for early assessment of the effects of platinum-based chemotherapeutic drugs on fish.

Degradation of methadone by the sunlight/FC process: Kinetics, radical species participation and influence of the water matrix

Free chlorine sunlight photolysis (sunlight/FC) markedly enhances the degradation rate of methadone, a synthetic opioid used medically, over that obtained using sunlight alone. The pseudo-first-order rate constants of methadone degradation under acidic conditions ([methadone] = 0.2 μM, [free chlorine] = 4 μM, and pH = 4) for sunlight/FC and sunlight photolysis are 7.0 ± 1.1 × 10^-2 min^-1 and 1.4 ± 0.2 × 10^-2 min^-1, respectively. The improved methadone degradation can be attributed to the production of HO and reactive chlorine species (RCS) during sunlight/FC photolysis. HO and RCS predominantly accounted for degradation during sunlight/FC photolysis under acidic and neutral conditions, while direct photolysis was the major contributor towards methadone degradation in alkaline conditions. The initial pH (pH 4-11) and free chlorine concentration (1-6 μM) significantly influenced the overall degradation efficiency of methadone. The presence of HCO₃^-, Cl^- and dissolved organic matters, which may competitively react with HO and RCS, retard the degradation of methadone in synthetic wastewater. Consequently, a 50% lower methadone degradation rate was observed when deionized (DI) water was replaced with tap water. These results emphasize the need to consider different water matrices when applying sunlight/FC photolysis for water treatment.