Germanium [Ge, 32]

Germanium is a metalloid of the group 14 in the periodic table of elements. Its concentration in the Earth’s crust averages 1.5 mg/kg. Its similar contents are present in igneous rocks. Germanium is an important commodity in several manufacturing sectors, such as fiber-optic and infrared optics. It is also used for polymerization catalysts, and in the production of nanowires and organometallic compounds. Its most important use is in the multijunction solar cells for satellites, and terrestrial-based solar concentrator systems and infrared devices. Main sources of germanium in the atmosphere are from coal-fired plants, metallurgical industries, and waste incineration. Its emission from coal burning in the United Kingdom was estimated at about 2 kt/yr. Certain compounds of germanium have low toxicity to mammals, but have high toxic effects against certain bacteria. In the absence of occupational exposure, food represents the most important source of germanium uptake for humans.