Tungsten

Abstract

Tungsten is a rare metal with numerous applications, most notably in machine tools, catalysts, and superalloys. The physical and chemical properties of tungsten and its compounds of commercial importance (such as sodium tungstate, ammonium meta ‐ and para ‐tungstate, tungsten metal, tungsten carbide, and tungsten oxides), as well as tungsten industrialization, recycling, occupational exposure, and biomonitoring are discussed. Between 1970 and 1990, most tungsten toxicological investigations concerned the toxicity and health effects of cemented carbides, also known as hard metal, rather than tungsten and its compounds themselves. However, within the last decade a diversity of studies on the toxicity of the water soluble and bioavailable sodium tungstate, have been conducted to fill several toxicity knowledge gaps. Acute toxicity studies on several soluble (sodium tungstate, ammonium para ‐ and meta ‐tungstate) and sparingly water‐soluble (tungsten metal, tungsten oxides, tungsten carbide) substances reported low acute oral, dermal, and inhalation toxicity, as well as a lack of eye and dermal irritation and sensitization potential. Studies published within the last 5–7 years on sodium tungstate include oral repeated exposure, reproductive, developmental, neurotoxicological, and immunotoxicological endpoints. Several reports have incorrectly associated repeated exposure toxicity of hard metals with pure tungsten carbide. As the toxicity of hard metal does not represent the intrinsic toxicity of tungsten substances so it is discussed separately within this chapter.