Vanadium revisited: Redox speciation linking exposure, biology, and toxicity

Vanadium is a multi-valent, redox-active transition metal whose biological effects are governed by dynamic redox speciation and cycling. Historically investigated for insulin-mimetic properties, vanadium has re-emerged as an environmental toxicant of increasing concern due to expanding exposure from industrial emissions, energy technologies, and particulate air pollution. Across physiological systems, interconversion between vanadyl and vanadate drives redox cycling, reactive oxygen species generation, and modulation of phosphorylation-dependent signaling pathways, influencing metabolic regulation, mitochondrial function, and tissue remodeling. Despite relatively low whole-body abundance and rapid systemic clearance, chronic exposure can lead to tissue-specific accumulation and redox imbalance, particularly in lungs, kidneys, and livers. Emerging evidence indicates that biological responses are not determined solely by the nominal oxidation state at exposure, but rather by in situ speciation shaped by ligand coordination, pH, and redox environment. These factors collectively determine cellular uptake, transformation, and downstream molecular effects. This short review synthesizes current understanding of vanadium redox chemistry in physiological contexts from toxicological perspectives. We propose that dynamic redox speciation represents the key principle linking environmental exposure to molecular mechanisms and disease risk, and we highlight key knowledge gaps necessary for advancing predictive toxicology and exposure-informed risk assessment. Finally, we highlight critical knowledge gaps and research priorities necessary to advance speciation-informed exposure biology, predictive toxicology, and risk assessment.