Mobilisation of Cr occurs mainly through air, water and soil. A report on a critical raw material profile by the European Commision in 2014 revealed that the forecast average annual demand for Cr growth of 3%-4.5% per year ( EC Report, 2014, Report on Critical raw materials for the EU). Within the EU, Finland was the main producer of Cr in 2006, producing over 99% of the total EU Cr production (219,500 tonnes). The main sources for EU imports in 2006 were South Africa (approximately 80%). Due to a lack of internal supply and to demand from the steel industry, the EU has been an importer of Cr ores. Major uses of Cr(VI) compounds include metal plating, manufacture of pigments and dyes, corrosion inhibitors, chemical synthesis, refractory production, leather tanning, and wood preservation ( Blade et al., 2007). Most of Cr(VI) compounds are man-made (products or by-products) and human-caused Cr(VI) contamination is a result of large industrial emissions (mainly from metallurgical, chemical, and refractory brick industries). The occurrence of Cr(VI) is rare naturally. Hexavalent form – Cr(VI) – is more toxic than trivalent form – Cr(III) for its high oxidizing potential – and easily penetrates biological membranes. The +3 and +6 forms are the most important as the +2, +4, and +5 forms are unstable and are rapidly converted to +3, which in turn is oxidized to +6 ( Towill et al. Chromium can exist in oxidation states ranging from -2 to +6, but is most frequently found in the environment in the trivalent (+3) and hexavalent (+6) oxidation states.
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