A comparative assessment of the acute inhalation toxicity of vanadium compounds

Abstract

Vanadium compounds have become important in industrial processes, resulting in workplace exposure potential and are present in ambient air as a result of fossil fuel combustion. A series of acute nose-only inhalation toxicity studies was conducted in both rats and mice in order to obtain comparative data on the acute toxicity potential of compounds used commercially. V₂O₃, V₂O₄, and V₂O₅, which have different oxidation states (+3, +4, +5, respectively), were delivered as micronized powders; the highly water-soluble and hygroscopic VOSO₄ (+4) could not be micronized and was instead delivered as a liquid aerosol from an aqueous solution. V₂O₅ was the most acutely toxic micronized powder in both species. Despite its lower overall percentage vanadium content, a liquid aerosol of VOSO₄ was more toxic than the V₂O₅ particles in mice, but not in rats. These data suggest that an interaction of characteristics, i.e., bioavailability, solubility and oxidation state, as well as species sensitivity, likely affect the toxicity potential of vanadium compounds. Based on clinical observations and gross necropsy findings, the lung appeared to be the target organ for all compounds. The level of hazard posed will depend on the specific chemical form of the vanadium. Future work to define the inhalation toxicity potential of vanadium compounds of various oxidation states after repeated exposures will be important in understanding how the physico-chemical and biological characteristics of specific vanadium compounds interact to affect toxicity potential and the potential risks posed to human health.

Keywords:

• Vanadium
• inhalation toxicity
• in-vitro solubility
• metal toxicity

Acknowledgements

The authors thank the technical staff at IIT Research Institute for performing the chemical characterization and inhalation exposures, the technical staff at LRRI, Dr. David White, Vice President Health Safety Environmental Affairs, AMG Advanced Metallurgical Group N.V. for his valuable chemistry assistance with the manuscript, Dr. Camille Stebbins, ATI, for her helpful review, and Dr. Andrey Nikiforov, President & Principal at Toxicology Regulatory Services for his technical oversight of these studies.

The views, opinions and findings contained in this research are those of the authors and do not necessarily reflect the views of the DoD and should not be construed as an official DoD/Army policy.

Declaration of interest

Judith A. MacGregor has served as a consultant to the vanadium and petroleum industries and served on a scientific review board for the Vanadium Safety Readiness Program, DOD.

Funding

This work was supported by the Vanadium Safety Readiness Program by ATI partnering with the Department of Defense (DoD) under an agreement awarded by the U.S. Army Medical Research and Materiel Command (USAMRMC), Fort Detrick, Maryland, Contract Number: W81XWH-09-2-006.

Notes

¹ ACGIH stands for the American Conference of Governmental Industrial Hygienists, which is a member-based organization that advances occupational and environmental health and sets worker exposure standards for chemical encountered in the workplace.

² TLV-TWA stands for the Threshold Limit Value time-weighted average, which is the average level of V₂O₅ in air that is permissible over an eight hour workday or a 40-hour work week.