The limitations of using the NTP chronic bioassay on vanadium pentoxide in risk assessments

Tuning Optical and Electrical Properties of Vanadium Oxide with Topochemical Reduction and Substitutional Tin

Vanadium oxides are widely tunable materials, with many thermodynamically stable phases suitable for applications spanning catalysis to neuromorphic computing. The stability of vanadium in a range of oxidation states enables mixed-valence polymorphs of kinetically accessible metastable materials. Low-temperature synthetic routes to, and the properties of, these metastable materials are poorly understood and may unlock new optoelectronic and magnetic functionalities for expanded applications. In this work, we demonstrate topochemical reduction of α-V2O5 to produce metastable vanadium oxide phases with tunable oxygen vacancies (>6%) and simultaneous substitutional tin incorporation (>3.5%). The chemistry is carried out at low temperature (65 °C) with solution-phase SnCl2, where Sn2+ is oxidized to Sn4+ as V5+ sites are reduced to V4+ during oxygen vacancy formation. Despite high oxygen vacancy and tin concentrations, the transformations are topochemical in that the symmetry of the parent crystal remains intact, although the unit cell expands. Band structure calculations show that these vacancies contribute electrons to the lattice, whereas substitutional tin contributes holes, yielding a compensation doping effect and control over the electronic properties. The SnCl2 redox chemistry is effective on both solution-processed V2O5 nanoparticle inks and mesoporous films cast from untreated inks, enabling versatile routes toward functional films with tunable optical and electronic properties. The electrical conductance rises concomitantly with the SnCl2 concentration and treatment time, indicating a net increase in density of free electrons in the host lattice. This work provides a valuable demonstration of kinetic tailoring of electronic properties of vanadium-oxygen systems through top-down chemical manipulation from known thermodynamic phases.

Toxicological evaluation of vanadium and derivation of a parenteral tolerable intake value for medical devices

Vanadium is used in alloys, batteries as well as catalyst and is a known impurity in medical devices and pharmaceuticals. The present work describes the calculation of a parenteral tolerable intake (TI) for vanadium by chronic exposure in implantable medical devices per ISO 10993-17:2023, the applicable standard. The 2023 update of ISO 10993-17 [1] introduces new uncertainty factors (UFs) for calculating a TI. Therefore, we noted differences between the ISO guidance and the ICH Q3D guidance on Permissible Daily Exposure (PDE) for parental elemental pharmaceutical impurities. We derived a TI of 0.20 μg V/kg/day based on the updated ISO guidance, and a PDE of 0.24 μg V/kg/day based on ICH guidance. The latter is considered a more realistic estimate.

Vanadium in the Environment: Biogeochemistry and Bioremediation

Vanadium(V) is a highly toxic multivalent, redox-sensitive element. It is widely distributed in the environment and employed in various industrial applications. Interactions between V and (micro)organisms have recently garnered considerable attention. This Review discusses the biogeochemical cycling of V and its corresponding bioremediation strategies. Anthropogenic activities have resulted in elevated environmental V concentrations compared to natural emissions. The global distributions of V in the atmosphere, soils, water bodies, and sediments are outlined here, with notable prevalence in Europe. Soluble V(V) predominantly exists in the environment and exhibits high mobility and chemical reactivity. The transport of V within environmental media and across food chains is also discussed. Microbially mediated V transformation is evaluated to shed light on the primary mechanisms underlying microbial V(V) reduction, namely electron transfer and enzymatic catalysis. Additionally, this Review highlights bioremediation strategies by exploring their geochemical influences and technical implementation methods. The identified knowledge gaps include the particulate speciation of V and its associated environmental behaviors as well as the biogeochemical processes of V in marine environments. Finally, challenges for future research are reported, including the screening of V hyperaccumulators and V(V)-reducing microbes and field tests for bioremediation approaches.

Vanadium: environmental hazard or environmental opportunity? A perspective on some key research needs

Vanadium remains an important microalloying element in the metallurgical industry and has more recently become important in energy storage. Such applications provide important opportunities in carbon reduction initiatives. They must be exploited safely and therefore understanding the toxicological profile of vanadium and its compounds, and ensuring ongoing regulatory efforts are appropriate is vital. This perspective details some of the technical challenges and common misconceptions in vanadium chemistry and toxicology and outlines knowledge gaps and areas of research that the authors believe must be addressed to achieve full benefit within a scientifically sound regulatory framework.