TiO2 photocatalytic degradation and transformation of oxazaphosphorine drugs in an aqueous environment

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.

Ozonation and UV photolysis for removing anticancer drug residues from hospital wastewater

The present study investigates the use of UV light and the ozone process for doxorubicin, daunorubicin, epirubicin, and irinotecan degradation. The process was carried out using different pH values in hospital wastewater. The use of UV radiation reduces the concentration of anticancer drugs, but in all cases, this technology was not able enough to remove on the whole these contaminants from hospital wastewater. The best condition was achieved when using pH 9 for most of the analytes. Doxorubicin, daunorubicin, and epirubicin were degraded at 97.3%, 88.3%, and 99.0%, respectively. Irinotecan showed the lowest degradation, just 55.6%; a slightly higher degradation (63.8%) was obtained when pH 5 was used. Complete removal of doxorubicin, daunorubicin, epirubicin, and irinotecan was achieved when ozone treatment was used for all the pH studied. The results indicated that UV light and the ozone process can be used as a tertiary treatment to reduce the concentration of anticancer drugs in the effluents. Ozonation, therefore, proved to be more efficient than the photolysis process, when considering the percentual degradation of the original compounds in shorter timespans.

Solar-driven photoelectrocatalytic degradation of anticancer drugs using TiO2 nanotubes decorated with SnS quantum dots

In recent years, the growing interest in applying photoelectrocatalysis (PEC) to decompose organic pollutants has resulted in the need to search for new photoelectrode materials with high activity under visible light radiation. The presented research showed an increased photoelectrocatalytic activity under sunlight of Ti/TiO₂ sensitized with SnS quantum dots, obtained by the successive ionic layer adsorption and reaction (SILAR) method. The presence of SnS caused the enhanced absorption of visible irradiation and the reduction of recombination of generated charges by a p-n heterojunction created with the TiO₂. The highest efficiency of photoelectrocatalytic degradation of anticancer drugs (ifosfamide, 5-fluorouracil, imatinib) was achieved for the SnS-Ti/TiO₂ photoelectrode with a SnS quantum dot size from 4 to 10 nm. In addition, a decrease of IF PEC degradation efficiency was observed with increasing pH and with the presence of Cl^-, NO₃^-, HCO₃^- and organic matter in the treated solution. Studies of the PEC mechanism have shown that drug degradation occurs mainly as a result of the direct and indirect action of photogenerated holes on the SnS-Ti/TiO₂ photoelectrode, and the identified degradation products allowed for the presentation of the degradation pathway of IF, 5-FU and IMB. Duckweed (Lemna minor) growth inhibition tests showed no toxicity of the drug solutions after treatment.

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.

Comparative physicochemical properties and toxicity of organic UV filters and their photocatalytic transformation products

Transformation products (TPs) of micropollutants contaminating our water resources have become an emerging issue due to the potential threats they pose to environmental and human health. This study investigated the transformation chemistry, toxicity, physicochemical properties and environmental behavior resulting from photocatalytic transformation of organic UV filters as model micropollutants. 3-Benzylidene camphor (3-BC), 4-hydroxybenzophenone (4-HB) and octocrylene (OC) were effectively degraded by UV-A/TiO₂ treatment, with TPs identified and characterized with high resolution mass spectrometry. Nitrated-TPs were observed to be formed in the presence of nitrite and nitrate for 3-BC and 4-HB, suggesting that the transformation process could be altered by components in the water matrix. Vibrio fischeri bioluminescence inhibition assay revealed an increase in toxicity of TPs derived from photocatalytic treatment, with quantitative structure-activity relationship model (ECOSAR) predicted an enhanced toxicity of individual TPs' after transformation. Assessment of physicochemical properties and environmental behavior suggested that TPs as compared to parent organic UV filters, may represent even greater hazards due to their increased water solubility, persistence and mobility - in addition to retaining the parent organic UV filter's toxicity. The results provide important information relevant to the potential risks for the selected organic UV filters, and their corresponding transformation products.

Degradation of cyclophosphamide during UV/chlorine reaction: Kinetics, byproducts, and their toxicity

Cyclophosphamide (CP) is a widely used anticancer drug and an immunosuppressant. Since CP is nonbiodegradable, it is hardly removed by the conventional wastewater treatment processes, resulting in continuous detection in surface water. In this study, the degradation of CP during the UV-B/chlorine reaction was investigated. CP was not degraded by UV-B photolysis and chlorination only but was effectively degraded in the UV-B/chlorine reaction with pseudo-first-order kinetics. Acidic pH conditions in the UV-B/chlorine reaction showed the most effective removal of CP. More than 56% of the CP was mineralized within 8 h of the reaction. Seven organic transformation products (TPs) (m/z = 141.01, 192.10, 198.03, 212.01, 258.01, 274.00, and 276.02, respectively) and four inorganic byproducts (NH₄⁺, NO₃^-, HCOO^-, and PO₄^3-) were identified using LC-qTOF/MS and ion chromatography, respectively. Microtox test based on bioluminescence inhibition showed that the toxicity inhibition increased to 88% as the reaction proceeded during the UV/chlorine reaction, probably due to the production of TPs, especially TP 258 (m/z = 258.01). The results of this study imply that the toxicity of TPs needs to be reduced when applying a UV-B/chlorination process to treat CP in water.

Threat and sustainable technological solution for antineoplastic drugs pollution: Review on a persisting global issue

In the past 20 years, the discharge of pharmaceuticals and their presence in the aquatic environment have been continuously increasing and this has caused serious public health and environmental concerns. Antineoplastic drugs are used in chemotherapy, in large quantities worldwide, for the treatment of continuously increasing cancer cases. Antineoplastic drugs also contaminate water sources and possess mutagenic, cytostatic and eco-toxicological effects on microorganisms present in the aquatic environment as well as on human health. Due to the recalcitrant nature of antineoplastic drugs, the commonly used wastewater treatment processes are not able to eliminate these drugs. Globally, various anticancer drugs are being consumed during chemotherapy in hospitals and households by out-patients. These anti-cancer agents enter the water bodies in their original form or as metabolites via urine and faeces of the out-patients or the patients admitted in hospitals. Due to its high lipid solubility, the antineoplastic drugs accumulate in the fatty tissues of the organisms. These drugs enter through the food chain and cause adverse health effects on humans due to their cytotoxic and genotoxic properties. The United States Environmental Protection Agency (US-EPA) and the Organization for Economic Cooperation and Development (OECD) elucidated new regulations for the management of hazardous pharmaceuticals in the water environment. In this paper, the role of antineoplastic agents as emerging water contaminants, its transfer through the food chain, its eco-toxicological properties and effects, technological solutions and management aspects were reviewed.

New insights into transformation pathways of a mixture of cytostatic drugs using Polyester-TiO2 films: Identification of intermediates and toxicity assessment

The photocatalytic activity of two bio-based polymer photocatalysts [poly(ethylene terephthalate)-TiO₂ (PET-TiO₂) and poly(L-lactic acid)-graphene oxide-TiO₂ (PLLA-GO-TiO₂)] towards Tamoxifen (TAM), Cyclophosphamide (CP), Cytarabine (CYT) and 5-Fluorouracil (5-FLU) removal was explored and compared. The highest photocatalytic activity for the degradation of the cytostatic drugs was accomplished by PET-TiO₂. Among the contaminants, TAM was the most easily removed, requiring 90 min for complete elimination, while CP showed the highest resistance to photocatalysis, not being completely removed after 6 h. Liquid chromatography coupled with high-resolution mass spectrometry analysis was employed for the identification of several transformation products (TPs) and potential pathways were proposed. A total of seventy (70) TPs including thirty-four (34) novel ones detected in AOPs were identified. The ecotoxicity of the mixture of the cytostatic drugs and TPs formed during the photocatalytic treatment was evaluated using Daphnia magna assay and was associated with the occurrence of specific TPs during the treatment process. The follow-up ECOSAR (Ecological Structure Activity Relationship) analysis further elucidated that only minor chemical transformations, such as the hydroxylation or the oxidative opening of an aromatic ring system, could hamper the adverse effects of cytostatic drugs in aquatic species. Such a comparative study on the mixture toxicity of cytostatics and their TPs is presented for the first time.

Radiolytic degradation of anticancer drug capecitabine in aqueous solution: kinetics, reaction mechanism, and toxicity evaluation

The occurrence of anticancer drugs in the environment has attracted wide attention due to its potential environmental risks. The aim of this study was to investigate degradation characteristics and mechanism of anticancer drug capecitabine (CPC) by electron beam (EB) irradiation. The results showed that EB was an efficient water treatment process for CPC. The degradation followed pseudo-first-order kinetics with dose constants ranged from 1.27 to 3.94 kGy^-1. Removal efficiencies in natural water filtered or unfiltered were lower than pure water due to the effect of water matrix components. The degradation was restrained by the presence of NO₂^-, NO₃^- and CO₃^2-, and fulvic acid due to competition of reactive radical •OH. It demonstrated that oxidizing radical played important role in irradiation process. The appropriate addition of H₂O₂ and K₂S₂O₈ providing with oxidizing agents •OH and •SO₄^- was favorable to improve degradation efficiency of CPC. The possible transformation pathways of CPC including cleavage of the ribofuranose sugar and defluorination were proposed based on intermediate products and were consistent with the theoretical calculation of charge and electron density distribution. Toxicity of CPC and intermediate products were estimated by ECOSAR program. It was found that CPC was transformed to low toxicity products with EB.

Insights into Mechanisms of Electrochemical Drug Degradation in Their Mixtures in the Split-Flow Reactor

The recirculating split-flow batch reactor with a cell divided into anolyte and catholyte compartments for oxidation mixture of cytostatic drugs (CD) was tested. In this study, kinetics and mechanisms of electrochemical oxidization of two mixtures: 5-FU/CP and IF/CP were investigated. The order of the CD degradation rate in single drug solutions and in mixtures was found to be 5-FU < CP < IF. In the 5-FU/CP mixture, k_app of 5-FU increased, while k_app of CP decreased comparing to the single drug solutions. No effect on the degradation rate was found in the CP/IF mixture. The presence of a second drug in the 5-FU/CP mixture significantly altered mineralization and nitrogen removal efficiency, while these processes were inhibited in IF/CP. The experiments in the different electrolytes showed that •OH and sulphate active species can participate in the drug's degradation. The k_app of the drugs was accelerated by the presence of Cl^- ions in the solution. Chlorine active species played the main role in the production of gaseous nitrogen products and increased the mineralisation. Good results were obtained for the degradation and mineralisation processes in mixtures of drugs in municipal wastewater-treated effluent, which is beneficial from the technological and practical point of view.

Photocatalytic degradation of cyclophosphamide and ifosfamide: Effects of wastewater matrix, transformation products and in silico toxicity prediction

Antineoplastic drugs have been identified in surface water and effluents from wastewater treatment and, once in the environment, may be harmful to aquatic organisms, as these compounds are possibly mutagenic, genotoxic, cytotoxic, carcinogenic and teratogenic. This work investigated the photodegradation of cyclophosphamide (CP) and ifosfamide (IF) using ruthenium doped titanate nanowires (Ru-TNW) in distilled water (DW) and in wastewater (WW) from secondary wastewater treatment, under UV-Vis radiation. The results indicated that Ru-TNW showed photocatalytic activity for the two cytotoxic drugs with the half-life (t_1/2) of 15.1 min for CP and 12.9 min for IF in WW. Four CP transformation products (TPs) and six IF TPs from the photodegradation process are here reported. These TPs were elucidated by high-resolution mass spectrometry. For both pollutants, the results showed different time profiles for the TPs when WW and DW were used as matrix. Overall, in the WW there was a higher production of TPs and two of them were detected only in this matrix. In other words, environmental matrices may produce different TPs. Degradation pathways were proposed and both drugs bear similarities. Additionally, in silico toxicity were performed by quantitative structure-activity relationship models. The predictions indicated that the TPs, with the exception of one IF TP, presented high mutagenic potential.

Removal, potential reaction pathways, and overall cost analysis of various pollution parameters and toxic odor compounds from the effluents of turkey processing plant using TiO2-assisted UV/O3 process

In the present study, removal of hazardous toxic odor compounds with color, COD and turbidity were concurrently investigated for the effluents of a turkey processing plant located in Bolu, Turkey. A hybrid TiO₂-assisted photo-ozonation (UV/TiO₂/O₃) process was set to address this issue. Subsequently, a comprehensive GC/MS method was developed for quantification of odor compounds. Finally, a complete overall cost analysis was incorporated with the findings of the study to demonstrate an economic analysis of the process. Descriptive results showed that the effluents had high pollution content in terms of color (0.374 IU; b = -0.06), COD (146 mg/L O₂) and turbidity (15.52 NTU). Moreover, dimethyl silanediol (DS, 34.3%), acetic acid (AA, 20.5%), and diisobutyl phthalate (DP, 32.5%) were determined as major odor compounds of the effluents. After UV/TiO₂/O₃ process, DS, AA, and DP were reduced to 12.4%, 12.0%, and 8.4%, respectively under the operating conditions of ozone dose of 16 mg/L, initial pH of 7.5, reaction time of 25 min, and catalyst dose of 3 g/L TiO₂. At the same conditions removal efficiencies of color, COD and turbidity were obtained %99, %85, and 78%, respectively. These values demonstrated the accuracy of UV/TiO₂/O₃ process in terms of removal of hazardous odor compounds and the other pollution parameters. Studies on reaction mechanism showed that main degradation mechanism occurred in three ways: formation of long-chained cyclic compounds from DS (1), formation of acetamide and ammonium acetate from AA (2), and formation of phthallic acid from DP (3). Finally, overall cost analysis showed that the current process costed 0.014 $ per 1 L of treated effluent and this value showed that the current process met the economic criteria in terms of feasibility.

Sonochemical Synthesis of Ce-doped TiO2 Nanostructure: A Visible-Light-Driven Photocatalyst for Degradation of Toluene and O-Xylene

Ce-doped TiO2 nanostructures (CeT) with different amounts of Ce (0.5, 0.75, 1.0, 1.5, and 2.0 wt.%) were synthesized using a sonochemical processing method. The physicochemical properties of the prepared samples were explored using UV-visible diffuse reflectance spectroscopy (UV-vis DRS), field-emission TEM (FE-TEM), XRD, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy (PL), and surface area and pore size analyzers. The photocatalytic performance of the prepared CeT was assessed by monitoring their degradation efficiencies for gaseous toluene and o-xylene-widely known as significant indoor air pollutants-under daylight irradiation. The prepared CeT exhibited significantly improved photocatalytic performance towards the degradation of toluene and o-xylene, which was much higher than that observed for pure TiO2 and commercial P25 TiO2. Particularly, photocatalytic degradation efficiencies by the prepared CeT catalysts increased remarkably in the case of o-xylene (up to 99.4%) compared to toluene (up to 49.1%). The degradation efficiency by the CeT was greatest for the CeT-0.75 sample, followed by, in order, CeT-1.0, CeT-0.5, CeT-1.5, and CeT-2.0 samples in agreement with the order of the surface area and the particle size of the catalysts. According to the change of light source, the average decomposition efficiencies for toluene and o-xylene by CeT-0.75 were shown in the order of conventional daylight lamp > violet light emitting diodes (LEDs) > white LEDs. The decomposition efficiencies normalized to supplied electric power, however, were estimated to be in the following order of violet LEDs > white LEDs > conventional daylight lamp, indicating that the LEDs could be a much more energy efficient light source for the photodecomposition of target toluene and o-xylene using the CeT-0.75 photocatalyst.

Cytostatic drug removal using electrochemical oxidation with BDD electrode: Degradation pathway and toxicity

In the presented study, electrochemical oxidation of five anticancer drugs (5-fluorouracil (5-FU), ifosfamide (IF), cyclophosphamide (CF), methotrexate (MTX), imatinib (IMB)) using boron doped diamond (BDD) electrode was investigated. In the first step the operating parameters of electrolysis were optimized. Studies have demonstrated a significant influence of applying current density, temperature, pH of solution and initial concentration of 5-FU on the process efficiency. A comparison of the decomposition rate of all the tested drugs showed a decrease in the pseudo-first order rate constants in the following order: k(IMB) > k(MTX) > k(CF) ≈ k(IF) > k(5-FU). Mineralization current efficiency (MCE) was determined for all the drugs based on the removal amount of total organic carbon (TOC) and their values decreased in the same order as values of drug degradation rate k. Based on the identified degradation products, electrochemical oxidation pathways of the decomposed drugs were proposed. In the case of CF, IF and 5-FU the degradation process occurred mainly through ketonization, hydroxylation and dehalogenation, while MTX and IMB were decomposed by attack of hydroxyl radicals on benzyl position in parent compounds. An important part of the research was the evaluation of eco-toxicity of electrochemically treated drug solutions against Lemna minor. Toxicity of initial 5-FU and MTX solutions towards L. minor were observed but after electrochemical treatment its toxicity decreased. The opposite trend was observed for CF and IF. In this case no significant toxicity was observed for the initial solutions of these drugs, while after electrochemical treatment an increase in growth inhibition of L. minor was found.

Potential risks from UV/H2O2 oxidation and UV photocatalysis: A review of toxic, assimilable, and sensory-unpleasant transformation products

UV based advanced oxidation processes (UV-AOPs) that efficiently eliminate organic pollutants during water treatment have been the subject of numerous investigations. Most organic pollutants are not completely mineralized during UV-AOPs but are partially oxidized into transformation products (TPs), thereby adding complexity to the treated water and posing risks to humans, ecological systems, and the environment. While the degradation kinetics and mechanisms of pollutants have been widely documented, there is little information about the risks associated with TPs. In this review, we have collated recent knowledge about the harmful TPs that are generated in UV/H₂O₂ and UV photocatalysis, two UV-AOPs that have been studied extensively. Toxic and assimilable TPs were ubiquitously observed in more than 80% of UV-AOPs of organic pollutants, of which the toxicity and assimilability levels changed with variations in the reaction conditions, such as the UV fluence and oxidant dosage. Previous studies and modeling assessments showed that toxic and assimilable TPs may be generated during hydroxylation, dealkylation, decarboxylation, and deamination. Among various reactions, TPs generated from dealkylation and decarboxylation were generally less and more toxic than the parent pollutants, respectively; TPs generated from decarboxylation and deamination were generally less and more assimilable than the parent pollutants, respectively. There is also potential concern about the sensory-unpleasant TPs generated by oxidations and subsequent metabolism of microorganisms. In this overview, we stress the need to include both the concentrations of organic pollutants and the evaluations of the risks from TPs for the quality assessments of the water treated by UV-AOPs.

Environmental behavior of 12 UV filters and photocatalytic profile of ethyl-4-aminobenzoate

Ethyl-4-aminobenzoate (Et-PABA) is currently used as a substitute for 4-aminobenzoate (PABA) in sunscreens and anesthetic ointments. Despite its widespread use and hydrophilicity, Et-PABA has never been found in environmental waters. This study, probed the occurrence of Et-PABA in both seawater and drinking water sources in Hong Kong, and evaluated its transformation products (TPs) and environmental fate via cumulative potency and photocatalytic profile analyses. Another 11 UV filters used in skin-care products were also studied. Et-PABA was not detected in any water sample. Four other UV filters were dominant at ng/L level in both seawater and drinking water sources. UHPLC-QTOF-MS was used to elucidate the structure of TPs. With high resolution accurate mass data and fragment rationalization, 11 Et-PABA TPs were characterized, including seven intermediates firstly proposed as TPs; two compounds were reported for the first time. It is proposed that photocatalysis induces transformation pathways of (de)hydroxylation, demethylation and molecular rearrangement. Luminescent bacteria tests showed decreasing toxicity with increasing irradiation of Et-PABA, suggesting that irradiation TPs are less toxic than the parent compound. Transformation of Et-PABA appears to explain why Et-PABA has not been detected in the natural environment.

The effects and the toxicity increases caused by bicarbonate, chloride, and other water components during the UV/TiO2 degradation of oxazaphosphorine drugs

The influences of HCO₃^-, Cl^-, and other components on the UV/TiO₂ degradation of the antineoplastic agents ifosfamide (IFO) and cyclophosphamide (CP) were studied in this work. The results indicated that the presence of HCO₃^-, Cl^-, NO₃^-, and SO₄^2- in water bodies resulted in lower degradation efficiencies. The half-lives of IFO and CP were 1.2 and 1.1 min and increased 2.3-7.3 and 3.2-6.3 times, respectively, in the presence of the four anions (initial compound concentration = 100 μg/L, TiO₂ loading =100 mg/L, anion concentration = 1000 mg/L, and pH = 8). Although the presence of HCO₃^- in the UV/TiO₂/HCO₃^- system resulted in a lower degradation rate and less byproduct formation for IFO and CP, two newly identified byproducts, P11 (M.W. = 197) and P12 (M.W. = 101), were formed and detected, suggesting that additional pathways occurred during the reaction of •CO₃^- in the system. The results also showed that •CO₃^- likely induces a preferred ketonization pathway. Besides the inorganic anions HCO₃^-, Cl^-, NO₃^-, and SO₄^2-, the existence of dissolved organic matter in the water has a significant effect and inhibits CP degradation. Toxicity tests showed that higher toxicity occurred in the presence of HCO₃^- or Cl^- during UV/TiO₂ treatment and within 6 h of reaction time, implying that the effects of these two anions should not be ignored when photocatalytic treatment is applied to treat real wastewater.

The role of bicarbonate anions in methotrexate degradation via UV/TiO2: Mechanisms, reactivity and increased toxicity

Bicarbonate anion (HCO₃^-) is a major constituent in wastewater and natural water matrices, and the aim of this study was to investigate its roles in the degradation of the antineoplastic agent methotrexate via UV/TiO₂. A comprehensive investigation of reaction mechanisms was performed by conducting scavenger experiments and substructure reactivity and Microtox^® toxicity tests. In the presence of HCO₃^-, the methotrexate degradation rate substantially increased, indicating the involvement of CO₃^-. The estimated second-order rate constants of methotrexate with CO₃^- and OH were 1.4 × 10⁷ M^-1 s^-1 and 8.7 × 10⁹ M^-1 s^-1, respectively. Both the valence hole (h_vb⁺) and OH resulted in the generation of CO₃^-. Initial transformation pathways of methotrexate were proposed, including the addition of atomic oxygen, hydroxylation, deamination, CC cleavage and CN cleavage. CN cleavage at the aniline moiety (the N(13) position) is the primary decomposition pathway, leading to an aminopterin yield of 43%. CO₃^- preferentially reacted with the 4-aminobenzamide (ABZ) moiety and generated toxic byproducts during the later stages of decomposition, which was not observed in the UV/TiO₂ system. The reactivity of the three methotrexate substructures decreased in the following order in the presence of HCO₃^-: ABZ ≫ DHP ≫ LG∼0; however, without HCO₃^-, the following order was observed: ABZ ∼ DHP > LG. The results of this work suggest that the increase in toxicity induced by the presence of HCO₃^- likely occurs in many other OH-based advanced oxidation processes in wastewater containing pharmaceutical cocktails with ABZ moieties.

Human metabolites and transformation products of cyclophosphamide and ifosfamide: analysis, occurrence and formation during abiotic treatments

This study describes a gas chromatography-mass spectrometry analytical method for the analysis of cytostatic cyclophosphamide (CP), ifosfamide (IF) and their selected metabolites/transformation products (TPs): carboxy-cyclophosphamide (carboxy-CP), keto-cyclophosphamide (keto-CP) and 3-dechloroethyl-ifosfamide/N-dechloroethyl-cyclophosphamide (N-decl-CP) in wastewater (WW). Keto-cyclophosphamide, CP and IF were extracted with Oasis HLB and N-decl-CP and carboxy-CP with Isolute ENV+ cartridges. Analyte derivatization was performed by silylation (metabolites/TPs) and acetylation (CP and IF). The recoveries and LOQs of the developed method were 58, 87 and 103 % and 77.7, 43.7 and 6.7 ng L(-1) for carboxy-CP, keto-CP and N-decl-CP, respectively. After validation, the analytical method was applied to hospital WW and influent and effluent samples of a receiving WW treatment plant. In hospital WW, levels up to 2690, 47.0, 13,200, 2100 and 178 ng L(-1) were detected for CP, IF, carboxy-CP, N-decl-CP and keto-CP, respectively, while in influent and effluent samples concentrations were below LOQs. The formation of TPs during abiotic treatments was also studied. Liquid chromatography-high-resolution mass spectrometry was used to identify CP and IF TPs in ultrapure water, treated with UV and UV/H2O2. UV treatment produced four CP TPs and four IF TPs, while UV/H2O2 resulted in five CPs and four IF TPs. Besides already known TPs, three novel TPs (CP-TP138a, imino-ifosfamide and IF-TP138) have been tentatively identified. In hospital WW treated by UV/O3/H2O2, none of the target metabolites/TPs resulted above LOQs.

Ecotoxicity and genotoxicity of cyclophosphamide, ifosfamide, their metabolites/transformation products and their mixtures

Cyclophosphamide (CP) and ifosfamide (IF) are commonly used cytostatic drugs that repress cell division by interaction with DNA. The present study investigates the ecotoxicity and genotoxicity of CP, IF, their human metabolites/transformation products (TPs) carboxy-cyclophosphamide (CPCOOH), keto-cyclophosphamide (ketoCP) and N-dechloroethyl-cyclophosphamide (NdCP) as individual compounds and as mixture. The two parent compounds (CP and IF), at concentrations up to 320 mg L(-1), were non-toxic towards the alga Pseudokirchneriella subcapitata and cyanobacterium Synecococcus leopoliensis. Further ecotoxicity studies of metabolites/TPs and a mixture of parent compounds and metabolites/TPs performed in cyanobacteria S. leopoliensis, showed that only CPCOOH (EC50 = 17.1 mg L(-1)) was toxic. The measured toxicity (EC50 = 11.5 mg L(-1)) of the mixture was lower from the toxicity predicted by concentration addition model (EC50 = 21.1 mg L(-1)) indicating potentiating effects of the CPCOOH toxicity. The SOS/umuC assay with Salmonella typhimurium revealed genotoxic activity of CP, CPCOOH and the mixture in the presence of S9 metabolic activation. Only CPCOOH was genotoxic also in the absence of metabolic activation indicating that this compound is a direct acting genotoxin. This finding is of particular importance as in the environment such compounds can directly affect DNA of non-target organisms and also explains toxicity of CPCOOH against cyanobacteria S. leopoliensis. The degradation study with UV irradiation of samples containing CP and IF showed efficient degradation of both compounds and remained non-toxic towards S. leopoliensis, suggesting that no stable TPs with adverse effects were formed. To our knowledge, this is the first study describing the ecotoxicity and genotoxicity of the commonly used cytostatics CP and IF, their known metabolites/TPs and their mixture. The results indicate the importance of toxicological evaluation and monitoring of drug metabolites as they may be for certain aquatic species more hazardous than parent compounds.

Photocatalytic mineralization of codeine by UV-A/TiO₂--Kinetics, intermediates, and pathways

This study investigated the photocatalytic degradation of codeine by UV-irradiated TiO2. The degradation kinetics was determined under varied conditions including the TiO2 loading, codeine concentration, and pH. Codeine and several reaction intermediates including morphine were identified and tracked during degradation using HPLC/MS-MS technique, along with TOC and IC measurements. Specifically, removal of 100 μg/L of spike codeine was complete in 3 min by contact with a 0.1 g/L suspension of TiO2 under UV irradiation at pH 7. The degradation kinetics of codeine was first-order with respect to both the catalyst TiO2 and the reactant codeine, with enhanced reaction rates with increasing pH up to pH 9. Mineralization of codeine was possible upon prolonged contact; near complete mineralization of 10 mg/L of codeine was achieved in 90 min with 0.1 g/L TiO2 under irradiation at pH 5, during which the organic nitrogen was converted to NH3-N (74%) and NO3-N (22%). Based on the identified intermediates, two degradation pathways were proposed of which one involved ipso-substitution followed by cleavage of the aromatic ring and another involved repeated hydroxylation of the codeine molecule followed by its fragmentation.

Simplified sonochemical preparation of titania embedded with selected metals for purification of benzene and toluene

Titania (TiO2) photocatalysts, each embedded with one of six metals (Ag, Ce, Co, Fe, Mg, and Mn), were prepared using a simplified ultrasonic process. The characteristics of the prepared metal-embedded TiO2 (metal-TiO2) were determined using transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, photoluminescence emission spectroscopy, UV-visible spectroscopy, and nitrogen adsorption-desorption. Except for Co-TiO2, the metal-TiO2 photocatalysts showed improved performance for the decomposition of gaseous benzene and toluene, which are two of the most problematic indoor air pollutants that can cause a variety of adverse health symptoms, under daylight lamp irradiation. Photocatalytic activity was greatest for the Mg-TiO2 sample, followed by, in order, the Ag-TiO2, Ce-TiO2, Fe-TiO2, Mn-TiO2, unmodified TiO2, and Co-TiO2 samples. Although Mg-TiO2 showed the least redshift in its light absorption and the highest electron-hole recombination rate among the metal-TiO2 photocatalysts, it yielded the highest photocatalytic activity, likely because of its increased adsorption capacity and anatase composition. The degradation of benzene and toluene over Mg-TiO2 improved as ultrasound treatment amplitude increased from 20 to 37 μm, then decreased gradually as amplitude was further increased to 49 μm. Degradation efficiency also improved as ultrasound operation time increased from 30 to 60 min, then decreased gradually as amplitude was further increased to 90 min. Overall, this process could be utilized to prepare metal-TiO2 photocatalysts with improved performance for the decomposition of gas phase pollutants under daylight lamp irradiation.