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

Degradation and mineralization of anti-cancer drugs Capecitabine, Bicalutamide and Irinotecan by UV-irradiation and ozone

The degradation of three anti-cancer drugs (ADs), Capecitabine (CAP), Bicalutamide (BIC) and Irinotecan (IRI), in ultrapure water by ozonation and UV-irradiation was tested in a bench-scale reactor and AD concentrations were measured through ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS). A low-pressure mercury UV (LP-UV) lamp was used and degradation by UV (λ = 254 nm) followed pseudo-first order kinetics. Incident radiation in the reactor was measured via chemical actinometry using uridine. The quantum yields (φ) for the degradation of CAP, BIC and IRI were 0.012, 0.0020 and 0.0045 mol Einstein-1, respectively. Ozone experiments with CAP and IRI were conducted by adding ozone stock solution to the reactor either with or without addition of tert-butanol (t-BuOH) as radical quencher. Using this experimental arrangement, no degradation of BIC was observed, so a semi-batch setup was employed for the ozone degradation experiments of BIC. Without t-BuOH, apparent second order reaction rate constants for the reaction of the ADs with molecular ozone were determined to be 3.5 ± 0.8 ∙ 103 L mol-1 s-1 (CAP), 7.9 ± 2.1 ∙ 10-1 L mol-1 s-1 (BIC) and 1.0 ± 0.3 ∙ 103 L mol-1 s-1 (IRI). When OH-radicals (∙OH) were quenched, rate constants were virtually the same for CAP and IRI. For BIC, a significantly lower constant of 1.0 ± 0.5 ∙ 10-1 L mol-1 s-1 was determined. Of the tested substances, BIC was the most recalcitrant, with the slowest degradation during both ozonation and UV-irradiation. The extent of mineralization was also determined for both processes. UV irradiation was able to fully degrade up to 80% of DOC, ozonation up to 30%. Toxicity tests with Daphnia magna (D. magna) did not find toxicity for fully degraded solutions of the three ADs at environmentally relevant concentrations.

Guidance document on the impact of water treatment processes on residues of active substances or their metabolites in water abstracted for the production of drinking water

This guidance document provides a tiered framework for risk assessors and facilitates risk managers in making decisions concerning the approval of active substances (AS) that are chemicals in plant protection products (PPPs) and biocidal products, and authorisation of the products. Based on the approaches presented in this document, a conclusion can be drawn on the impact of water treatment processes on residues of the AS or its metabolites in surface water and/or groundwater abstracted for the production of drinking water, i.e. the formation of transformation products (TPs). This guidance enables the identification of actual public health concerns from exposure to harmful compounds generated during the processing of water for the production of drinking water, and it focuses on water treatment methods commonly used in the European Union (EU). The tiered framework determines whether residues from PPP use or residues from biocidal product use can be present in water at water abstraction locations. Approaches, including experimental methods, are described that can be used to assess whether harmful TPs may form during water treatment and, if so, how to assess the impact of exposure to these water treatment TPs (tTPs) and other residues including environmental TPs (eTPs) on human and domesticated animal health through the consumption of TPs via drinking water. The types of studies or information that would be required are described while avoiding vertebrate testing as much as possible. The framework integrates the use of weight-of-evidence and, when possible alternative (new approach) methods to avoid as far as possible the need for additional testing.

Toxicological aspect of water treated by chlorine-based advanced oxidation processes: A review

As well established in the literature, residual toxicity is an important parameter for evaluating the sanitary and environmental safety of water treatment processes, and this parameter becomes even more crucial when chlorine-based processes are applied for water treatment. Eliminating initial toxicity or preventing its increase after water treatment remains a huge challenge mainly due to the formation of highly toxic disinfection by-products (DBPs) that stem from the degradation of organic contaminants or the interaction of the chlorine-based oxidants with different matrix components. In this review, we present a comprehensive discussion regarding the toxicological aspects of water treated using chlorine-based advanced oxidation processes (AOPs) and the recent findings related to the factors influencing toxicity, and provide directions for future research in the area. The review begins by shedding light on the advances made in the application of free chlorine AOPs and the findings from studies conducted using electrochemical technologies based on free chlorine generation. We then delve into the insights and contributions brought to the fore regarding the application of NH₂Cl- and ClO₂-based treatment processes. Finally, we broaden our discussion by evaluating the toxicological assays and predictive models employed in the study of residual toxicity and provide an overview of the findings reported to date on this subject matter, while giving useful insights and directions for future research on the topic.

Appraising efficacy of existing and advanced technologies for the remediation of beta-blockers from wastewater: A review

The discharge of emerging pollutants, such as beta-blockers (BB), has been recognized as one of the major threats to the environment due to the ecotoxicity associated with these emerging pollutants. The BB are prescribed to treat high blood pressure and cardiovascular diseases; however, even at lower concentration, these pollutants can pose eco-toxic impacts towards aquatic organisms. Additionally, owing to their recalcitrant nature, BB are not effectively removed through conventional technologies, such as activated sludge process, trickling filter and moving bed bioreactor; thus, it is essential to understand the degradation mechanism of BB in established as well as embryonic technologies, like adsorption, electro-oxidation, Fenton process, ultraviolet-based advance oxidation process, ozonation, membrane systems, wetlands and algal treatment. In this regard, this review articulates the recalcitrant nature of BB and their associated removal technologies. Moreover, the major advantages and limitations of these BB removal technologies along with the recent advancements with regard to the application of innovative materials and strategies have also been elucidated. Therefore, the present review intends to aid the researchers in improving the BB removal efficiency of these technologies, thus alleviating the problem of the release of BB into the environment.

Environmental degradation of human metabolites of cyclophosphamide leads to toxic and non-biodegradable transformation products

The present study assessed the ready biodegradability of the prodrug cyclophosphamide (CPA) and its stable human metabolites in the closed bottle test (CBT). The results of the CBT showed that only the main human metabolite, carboxyphosphamide (CXP), was biodegradable to a certain extent (23 ± 2.4 % ThOD_NH3). All other metabolites showed neither biodegradation under these conditions nor were any toxic effects on the inoculum observed. Yet, HRMSⁿ results revealed partial primary elimination of all human metabolites and formation of 25 new transformation products. Abiotic degradation via S_Ni and S_N2 reactions was proposed as the main degradation pathway during the CBT. The main degradation products were assigned as 3-(2-chloroethyl)oxazolidin-2-one (COAZ), cytotoxic N-2-chloroethylaziridine (CEZ) and nor‑nitrogen mustard (NNM), an analogue of the chemical warfare agent HN2. While the acute ecotoxicity of the detected products is widely unknown, many have already been reported in medical literature to be either mutagenic, genotoxic, cytotoxic or carcinogenic and may therefore cause a greater risk than their precursors. QSAR models predicted that 16 of them are mutagenic and genotoxic, thus classifying the majority of the chemicals as potential environmental hazards. The central intermediates during the degradation process were proposed as CEZ and its corresponding aziridinium ion. However, other degradation products may occur depending on the type and strength of nucleophiles present in the matrices. Overall, the results demonstrated the importance to include human metabolites in the evaluation of the environmental fate of pharmaceuticals and their risk assessment especially when investigating prodrugs. The results underline the importance of identifying possible degradation products of metabolites, as they can be more toxic than related parent compounds and metabolites and can cause a greater risk to the environment and humans.

Investigation of the Degradation Behavior of Cyclophosphamide by Catalytic Ozonation Based on Mg(OH)2

Metal hydroxides, owing to their catalytic active sites for the decomposition of O3 to Reactive Oxygen Species (ROS), have been adapted for catalytic ozonation of micropollutants in wastewater. In this study, commercial Mg (OH)2 was used for the degradation of cyclophosphamide (CYP) by ozone. The crystal phase was confirmed by X-ray powder Diffraction (XRD). Percent degradation of 10 ppm CYP after 30 min by O3 and Mg (OH)2/O3 was 56 and 93, respectively, suggesting enhanced decomposition of O3 to ROS by the catalyst. The presence of ROS was further confirmed using pCBA as a probe, which showed that the concentration of ROS was eight times higher in the presence of Mg (OH)2/O3 than O3 alone. Catalytic ozonation experiments in the presence of scavengers showed that OH· radicals play a significant role in the degradation of CYP. The catalyst was found to be reusable for at least three cycles without significant loss in degradation efficiency. To study the compatibility of Mg (OH)2 for wastewater treatment applications, synthetic effluent was spiked with CYP and subjected to ozonation by Mg(OH)2/O3. The TOC of CYP before and after the treatment showed that Mg (OH)2/O3 not only degrades CYP but also mineralizes to a certain extent unlike O3 alone.

Solar-driven free chlorine advanced oxidation process for simultaneous removal of microcontaminants and microorganisms in natural water at pilot-scale

Contamination of natural water (NW) by emerging contaminants has been widely pointed out as one of the main challenges to ensure high-quality drinking water. Thus, the effectiveness of a solar-driven free chlorine advanced oxidation process simultaneously investigating the elimination of six organic microcontaminants (OMCs) and three bacteria from NW at a pilot-scale was evaluated in this study. Firstly, the solar/free chlorine process was studied at lab-scale using a solar simulator to evaluate the effect of free chlorine concentration (0.5-10 mg L^-1) on OMC degradation and generation of toxic oxyanions (e.g., ClO₃^- ions). Thus, the best free chlorine concentration observed was applied for the simultaneous removal of OMCs and pathogens under natural solar light at pilot scale. At lab-scale, the solar/free chlorine (2.5 mg L^-1) process achieved 80% of total degradation in 5 min (1.4 kJ L^-1 of accumulative UV energy) with an oxidant consumption of 0.3 mg L^-1 and without ClO₃^- generation. Similar results were attained under natural solar irradiation at a pilot-scale. For all bacteria strains, the legally required detection limit (DL = 1 CFU 100 mL^-1) for reclaimed water reuse was attained in a short contact time. Still, more importantly, the solar/free chlorine (2.5 mg L^-1) process effectively avoided the possible bacterial regrowth in the post-treated sample after six days. Finally, the combination of free chlorine with solar irradiation provided a simple and energy-efficient process for OMC and bacteria removal in NW at a pilot-scale.