Germanium dioxide

Endpoint summary

Description of key information

Important note:

All the data and information in this section relate to Germanium and its compounds in general. Concentrations are expressed as "germanium", not as specific Ge-substance. So, the data are relevant for Ge-substances in general.

Natural occurence of germanium

Germanium is a ‘metalloid’ element and a member of group 14 of the periodic table, along with C, Si, Sn and Pb. The element has three main oxidation states (-4, +2 and +4), of which +4 is the most common in nature. Germanium is a rare element, although relatively high levels have been found in several sulphide minerals, such as the copper minerals chalcopyrite CuFeS2, enargite Cu3AsS4, bornite Cu5FeS4 and tennantite (Cu,Fe)12As4S13, and others, such as low-temperature sphalerites (Zn,Fe)S and galena PbS. There are a few Ge minerals, including reniérite Cu3(Fe,Ge)S4, briartite Cu2(FeGe)S4, germanite Cu3(Ge,Fe)S4 and argyrodite Ag8GeS6 (FOREGs 2005).

Environmental forms of Ge and relevance to toxicity

Germanium occurs mostly as oxidation state +4 in nature. While all environmental concentration data are expressed as “Germanium", toxicity is predominantly related to the Ge⁺⁴ion. For this reason, the sections on human toxicity and ecotoxicity are applicable to all Ge-compounds, from which Ge-ions are released into the environment.

The (eco-)toxicity of Ge compounds is dependent on their capacity to release the Ge-ion. This is tested with the transformation/dissolution (T/D) test for Ge and GeO2. The results of this T/D test are presented in IUCLID section 4.8.

Similar to well documented processes for mono- (Ag), di- (Cd, Cu, Ni, Pb, Zn), and tri-valent (Al, Fe) metals, when germanium ions are formed in the environment, they will further interact with the environmental matrix and biota. As such, the concentration of Ge- ions that is available to organisms, the bioavailable fraction, will depend on processes like dissolution, absorption, precipitation, complexation, inclusion into (soil) matrix, etc. These processes are defining the fate of germanium in the environment and, ultimately, its ecotoxic potential. This has been recognised e.g. in the guidance to the CLP regulation 1272/2008 (metals annex):“Environmental transformation of one species of a metal to another species of the same does not constitute degradation as applied to organic compounds and may increase or decrease the availability and bioavailability of the toxic species. However as a result of naturally occurring geochemical processes metal ions can partition from the water column. Data on water column residence time, the processes involved at the water – sediment interface (i. e. deposition and re-mobilisation) are fairly extensive, but have not been integrated into a meaningful database. Nevertheless, using the principles and assumptions discussed above in Section IV.1, it maybe possible to incorporate this approach into classification.“

The issue of degradation (IUCLID section 5.2.) is not applicable to inorganic compounds.

Environmental concentrations

The crustal abundance of Ge is estimated to be 1.5 mg kg-1 (FOREGs 2005). Coal can contain substantially higher amounts, up to several hundred mg kg-1 Ge. For this reason coal ashes are often strongly enriched in Ge; the highest reported value of 0.66% Ge came from Italian lignite. Germanium is generally present in natural water at concentrations less than 1 ng l-1 (Jin et al. 1991). In soil, Ge is partly mobilised in the form of Ge(OH)2, but is readily fixed as Ge(OH)4 by clay minerals, Fe oxides and organic matter (Kabata-Pendias 2001). Its global abundance in soil is about 1 mg kg-1 (FOREGs 2005).

Median concentration of dissolved Ge in EU natural waters, not influenced by point source emissions is 0.009µg Ge/l ; the 10P and 90P values are ~= 0.005 µg Ge/l and ~= 0.030 µg Ge/l, respectively (FOREGs 2005). Some further present-day environmental levels relevant for the EU environment are reported in IUCLID section 5.5.