efsa-opinion-chromium-food-drinking-water

Chromium in food and drinking water
• FeCr 2 O 4 + 4 C → Fe + 2 Cr + 4 CO
Ferrochrome is commonly used as a raw material to produce stainless steel, a popular corrosion-proof
alloy usually formed by adding chromium to iron in concentrations above 11 %. To obtain pure
chromium different methods exist. For instance, chromite can be treated with oxygen in molten alkalis
to oxidize Cr(III) to the hexavalent oxidation state (Cr 6+ or Cr(VI); CAS registry 18540-29-9). The
latter (chromate) is dissolved in water and eventually precipitated as sodium dichromate: this is
reduced to Cr(III) oxide which, in turn, is reduced with aluminium to the pure metal (aluminothermic
method):
• Na 2 Cr 2 O 7 + 2 C → Cr 2 O 3 + Na 2 CO 3 + CO
• Cr 2 O 3 + 2 Al → 2 Cr + Al 2 O 3
Chromite ore and chromite concentrates are produced mainly by South Africa and, to a lesser but
similar extent, India and Kazakhstan: these countries together accounted for some 70 % of total world
production (approximately 24 × 10 6 metric tonnes) in 2008. Other important producers are Albania,
Brazil, Finland, and Turkey. In the same year, over 90 % of the global chromite production was
converted to ferrochrome for metallurgical applications (Korinek and Kim, 2010).
1.1.2. Uses and applications
Most chromium produced today is used in alloys, including stainless steel, a metal with wide
applications. Chromium is also used to cover the surface of other metals by electroplating
(specifically, chrome-plating) to protect the base metal from corrosion and give the surface a lustrous
appearance. Some chromium is also used to make refractory bricks, a material that can withstand very
high temperatures such as those of high-temperature ovens. Chromium and its salts are used in the
leather tanning industry, the manufacture of catalysts, pigments, paints, and fungicides/pesticides, the
ceramic and glass industry, the production of synthetic ruby and recording tapes, photography, and as
laboratory reagents. Cr(III) organic complexes, such as Cr(III) nicotinates and picolinate (Figures 1a
and b), are used as nutritional supplements for human use (EFSA, 2008a; EFSA ANS Panel 2010a). A
selection of chromium compounds is presented in Table 1.
Figure 1: Chemical structures of chromium trinicotinate (a) and chromium picolinate (b).
EFSA Journal 2014;12(3):3595 12