Reaction kinetics of corrinoid-mediated deiodination of iodinated X-ray contrast media and other iodinated organic compounds

Can reductive deiodination improve the sorption of iodinated X-ray contrast media to aquifer material during bank filtration?

Iodinated X-ray contrast media (ICM) as well as their aerobic transformation products (TPs), are highly polar triiodobenzoic acid derivatives, ubiquitously found in the urban water cycle. Based on their polarity, their sorption affinity to sediment and soil is negligible. However, we hypothesize that the iodine atoms bound to the benzene ring play a decisive role for sorption, due to their large atom radius, high electron number and symmetrical positioning within the aromatic system. The aim of this study is to investigate, if the (partial) deiodination, occurring during anoxic/anaerobic bank filtration, improves the sorption to aquifer material. Tri, di, mono and deiodinated structures of two ICMs (iopromide and diatrizoate) and one precursor/TP of ICM (5-amino-2,4,6-triiodoisophtalic acid) were tested in batch experiments, using two aquifer sands and a loam soil with and without organic matter. The di, mono and deiodinated structures were produced by (partial) deiodination of the triiodinated initial compounds. The results demonstrated that the (partial) deiodination increases the sorption to all tested sorbents, even though the theoretical polarity increases with decreasing number of iodine atoms. Whereas lignite particles positively affected the sorption, mineral components decreased it. Kinetics tests show biphasic sorption for the deiodinated derivatives. We have concluded that iodine affects the sorption by sterical hindrance, repulsive forces, resonance and inductive effects, depending on the number and position of iodine, side chain characteristics and composition of the sorbent material. Our study has revealed an increased sorption potential of ICMs and their iodinated TPs to aquifer material during anoxic/anaerobic bank filtration as a result of (partial) deiodination, whereby a complete deiodination is not necessary for efficient removal by sorption. Furthermore, it suggests that the combination of an initial aerobic (side chain transformations) and a subsequent anoxic/anaerobic (deiodination) redox milieu supports the sorption potential.

Removal of Iodine-Containing X-ray Contrast Media from Environment: The Challenge of a Total Mineralization

Iodinated X-ray contrast media (ICM) as emerging micropollutants have attracted considerable attention in recent years due to their high detected concentration in water systems. It results in environmental issues partly due to the formation of toxic by-products during the disinfection process in water treatment. Consequently, various approaches have been investigated by researchers in order to achieve ICM total mineralization. This review discusses the different methods that have been used to degrade them, with special attention to the mineralization yield and to the nature of formed by-products. The problem of pollution by ICM is discussed in the first part dedicated to the presence of ICM in the environment and its consequences. In the second part, the processes for ICM treatment including biological treatment, advanced oxidation/reductive processes, and coupled processes are reviewed in detail. The main results and mechanisms involved in each approach are described, and by-products identified during the different treatments are listed. Moreover, based on their efficiency and their cost-effectiveness, the prospects and process developments of ICM treatment are discussed.

Image quality and diagnostic accuracy of different dosages of iodixanol in computed tomography angiography and perfusion of overweight patients with coronary artery stenosis: A feasibility study

OBJECTIVES

Iodixanol contrast media with different doses using computed tomography angiography (CTA) and perfusion (CTP) to diagnose coronary artery disease (CAD) in overweight patients lacks assessment. Our study compared iodixanol 320 mg I/ml and 270 mg I/ml on image quality and accuracy of CTA combined CTP (CTA-CTP) to diagnose CAD.

METHODS

Overweight patients with suspected of CAD were randomized into iodixanol 270 group (received iodixanol 270 mg I/ml) and iodixanol 320 group (received iodixanol 320 mg I/ml). Based on these characteristics data, receiver operating characteristic (ROC) curve and corresponding area under the curve (AUC) were plotted to assess the sensitivity and specificity of the two administrations.

RESULTS

The subjective definition score, signal to noise ratio, and CT value of aorta in iodixanol 320 group were higher than iodixanol 270 group. In iodixanol 270 group: the image exhibited a normal state of both vessels and myocardial perfusion; and the AUC, specificity, and sensitivity were 0.376, 66.67, and 80.46, respectively. In iodixanol 320 group: the image exhibited a diameter stenosis in right coronary artery and myocardial infarction of inferior wall and proximal inferior wall septum, as well as myocardial perfusion defects; and the AUC, specificity, and sensitivity in iodixanol 320 group were 0.824, 75.00, and 89.87, respectively.

CONCLUSION

Accuracy and image quality of iodixanol 320 mg I/ml in the diagnosis of CAD with CTA-CTP was higher than using iodixanol 270 mg I/ml.

Comprehensive review on iodinated X-ray contrast media: Complete fate, occurrence, and formation of disinfection byproducts

Iodinated contrast media (ICM) are drugs which are used in medical examinations for organ imaging purposes. Wastewater treatment plants (WWTPs) have shown incapability to remove ICM, and as a consequence, ICM and their transformation products (TPs) have been detected in environmental waters. ICM show limited biotransformation and low sorption potential. ICM can act as iodine source and can react with commonly used disinfectants such as chlorine in presence of organic matter to yield iodinated disinfection byproducts (IDBPs) which are more cytotoxic and genotoxic than conventionally known disinfection byproducts (DBPs). Even highly efficient advanced treatment systems have failed to completely mineralize ICM, and TPs that are more toxic than parent ICM are produced. This raises issues regarding the efficacy of existing treatment technologies and serious concern over disinfection of ICM containing waters. Realizing this, the current review aims to capture the attention of scientific community on areas of less focus. The review features in depth knowledge regarding complete environmental fate of ICM along with their existing treatment options.

Comparison of UV-induced AOPs (UV/Cl2, UV/NH2Cl, UV/ClO2 and UV/H2O2 ) in the degradation of iopamidol: Kinetics, energy requirements and DBPs-related toxicity in sequential disinfection processes

The UV-induced advanced oxidation processes (AOPs, including UV/Cl₂, UV/NH₂Cl, UV/ClO₂ and UV/H₂O₂ ) degradation kinetics and energy requirements of iopamidol as well as DBPs-related toxicity in sequential disinfection were compared in this study. The photodegradation of iopamidol in these processes can be well described by pseudo-first-order model and the removal efficiency ranked in descending order of UV/Cl₂  > UV/H₂O₂  > UV/NH₂Cl > UV/ClO₂  > UV. The synergistic effects could be attributed to diverse radical species generated in each system. Influencing factors of oxidant dosage, UV intensity, solution pH and water matrixes (Cl^- , NH₄ ⁺ and nature organic matter) were evaluated in detail. Higher oxidant dosages and greater UV intensities led to bigger pseudo-first-order rate constants (K_obs) in these processes, but the pH behaviors exhibited quite differently. The presence of Cl^- , NH₄ ⁺ and nature organic matter posed different effects on the degradation rate. The parameter of electrical energy per order (EE/O) was adopted to evaluate the energy requirements of the tested systems and it followed the trend of UV/ClO₂  > UV > UV/NH₂Cl > UV/H₂O₂  > UV/Cl₂ . Pretreatment of iopamidol by UV/Cl₂ and UV/NH₂Cl clearly enhanced the production of classical disinfection by-products (DBPs) and iodo-trihalomethanes (I-THMs) during subsequent oxidation while UV/ClO₂ and UV/H₂O₂ exhibited almost elimination effect. From the perspective of weighted water toxicity, the risk ranking was UV/NH₂Cl > UV/Cl₂ > UV > UV/H₂O₂ > UV/ClO₂ . Among the discussed UV-driven AOPs, UV/Cl₂ was proved to be the most cost-effective one for iopamidol removal while UV/ClO₂ displayed overwhelming advantages in regulating the water toxicity associated with DBPs, especially I-THMs. The present results could provide some insights into the application of UV-activated AOPs technologies in tradeoffs between cost-effectiveness assessment and DBPs-related toxicity control of the disinfected waters containing iopamidol.

Deiodination in the presence of Dehalococcoides mccartyi strain CBDB1: comparison of the native enzyme and co-factor vitamin B12

Triiodinated benzoic acid derivatives are widely used as contrast media for medical examinations and are found at high concentrations in urban aquatic environments. During bank filtration, deiodination of iodinated contrast media has been observed under anoxic/anaerobic conditions. While several bacterial strains capable of dechlorination and debromination have been isolated and characterized, deiodination has not yet been shown for an isolated strain. Here, we investigate dehalogenation of iodinated contrast media (ICM), triiodobenzoic acids (TIBA), and analogous chlorinated compounds by Dehalococcoides mccartyi strain CBDB1 and its corrinoid co-factor vitamin B₁₂. No cell growth of CBDB1 was observed using iodinated compounds as electron acceptor. Only negligible deiodination occurred for ICM, whereas 2,3,5-TIBA was nearly completely deiodinated by CBDB1 without showing cell growth. Furthermore, TIBA inhibited growth with hexachlorobenzene which is usually a well-suited electron acceptor for strain CBDB1, indicating that TIBA is toxic for CBDB1. The involvement of CBDB1 enzymes in the deiodination of TIBA was verified by the absence of deiodination activity after heat inactivation. Adding iodopropane also inhibited the deiodination of TIBA by CBDB1 cells, indicating the involvement of a corrinoid-enzyme in the reductive TIBA deiodination. The results further suggest that the involved electron transport is decoupled from proton translocation and therefore growth. Graphical abstract.

Is the Hyporheic Zone Relevant beyond the Scientific Community?

Rivers are important ecosystems under continuous anthropogenic stresses. The hyporheic zone is a ubiquitous, reactive interface between the main channel and its surrounding sediments along the river network. We elaborate on the main physical, biological, and biogeochemical drivers and processes within the hyporheic zone that have been studied by multiple scientific disciplines for almost half a century. These previous efforts have shown that the hyporheic zone is a modulator for most metabolic stream processes and serves as a refuge and habitat for a diverse range of aquatic organisms. It also exerts a major control on river water quality by increasing the contact time with reactive environments, which in turn results in retention and transformation of nutrients, trace organic compounds, fine suspended particles, and microplastics, among others. The paper showcases the critical importance of hyporheic zones, both from a scientific and an applied perspective, and their role in ecosystem services to answer the question of the manuscript title. It identifies major research gaps in our understanding of hyporheic processes. In conclusion, we highlight the potential of hyporheic restoration to efficiently manage and reactivate ecosystem functions and services in river corridors.