Niobium [Nb, 41]

Niobium is a soft, gray transition metal of group 4 in the periodic table of elements, with physical and chemical properties similar to those of Ta, the metal of the same group. Niobium is also added to alloys used for surgical implants and in the stomatology. Its amounts in soils depend mainly on its contents in mother rocks. The behavior of Niobium during weathering highly depends on host minerals; therefore, it may be released from some minerals or may remain within resistant minerals. Once inhaled, it resides primarily in the lungs and can be absorbed into bones. Niobium and its compounds cause skin and eye irritation and can be toxic, but human poisoning has not been reported. The inhalation of niobium pentoxide and nitride results in scarring of the lungs in laboratory animals. Niobium is relatively mobile under humid conditions, and therefore may be available to plants.