ABSTRACT
This chapter provides a detailed discussion on the occurrence and production, uses, chemical and physical properties, exposure and exposure limits, toxicokinetics, and effects of niobium in humans. About as abundant in the earth's crust as nickel, niobium occurs with tantalum in the minerals tantalite, columbite, tantalocolumbite, and pyrochlore. Little Nb-bearing ore is mined in the United States; most is imported from Brazil, Nigeria, and Malaysia. Recovery is complex and varied in trying to separate the very similar Nb and Ta. Niobium or, as it is better known in the metallurgical industry, columbium is used in high-temperature steel alloys, in chrome-nickel-steel alloys to prevent the formation of chromium carbide, in some high-iron aluminum alloys, and in some permanent magnet alloys. The effects of niobium in humans include information on acute toxicity, chronic toxicity, biochemistry, specific organs and systems, teratogenicity, mutagenicity, and carcinogenicity.
