efsa-opinion-chromium-food-drinking-water

Chromium in food and drinking water
ASSESSMENT
1. Introduction
Chromium (Cr) was discovered in the second half of the 18th century: its elemental state and
compounds have been the subject of extensive research, also due to their diverse industrial
applications. It occurs in a variety of valence states with trivalent (Cr(III)) and hexavalent (Cr(VI))
being the most stable and biologically relevant oxidation states. For the general population, food is the
major source of exposure to chromium (> 90 % of the total intake). Drinking water may also be a
substantial source of exposure if chromium levels are exceptionally high. Cr(III) is a natural dietary
constituent present in a variety of foods and also in dietary supplements. Conversely, Cr(VI) seems to
be absent in food and its presence in drinking water is usually a consequence of anthropogenic
activity. Over the last years there have been several reports of naturally occurring Cr(VI) in
groundwater. Although in most cases the Cr(VI) concentrations found appear to be in the order of a
few µg/L or some tens of µg/L, values of a few hundreds of µg/L are not unusual.
Chromium absorption after dietary exposure in humans is relatively low (< 10 % of the ingested dose)
and is affected by the valence state and the nature of its ligands. Cr(VI) is reduced in the stomach to
Cr(III), which lowers the absorbed dose from ingested Cr(VI). The interconversion of the two species
is of relevance for risk assessment since, in general, Cr(VI) compounds are more toxic than Cr(III)
compounds. This is mostly due to the more effective cellular uptake of Cr(VI) as compared to Cr(III).
Cr(III) presents a low oral toxicity due to poor bioavailability. Oral exposure to Cr(VI) compounds is
associated with gastrointestinal system cancers in experimental animals. In humans, Cr(VI) is a known
carcinogen by the inhalation route of exposure and Cr(VI) compounds are classified by the
International Agency for Research on Cancer (IARC) as carcinogenic to humans (Group 1).
There are no maximum levels (MLs) set for chromium in food. A parametric value of 50 μg Cr/L for
total chromium in water intended for human consumption and a Maximum Limit of 50 μg Cr/L for
total chromium in natural mineral waters are laid down in Council Directive 98/83/EC and in
Commission Directive 2003/40/EC, respectively.
In March 2012, the European Food Safety Authority (EFSA) received a mandate from the Hellenic
Food Authority (EFET) for a scientific opinion on estimation of the risk to human health from the
presence total Cr in food and Cr(VI) in bottled water. This scientific opinion addresses the risks for
public health related to the presence of total Cr in food and Cr(VI) in water intended for human
consumption and natural mineral waters.
1.1. Chemistry and physico-chemical properties
In this Section, a summary of the current knowledge on a number of physico-chemical, environmentrelated
properties of chromium is given. Due to the very large number of scientific publications,
technical reports and reviews, and educational and press releases available on these topics, no
references are provided in the text unless specifically required. For additional detailed information, a
number of general scientific references are available (e.g. Papp and Lipin, 2001; WHO, 2003;
OEHHA, 2011; Saha et al., 2011; Zhitkovich, 2011; ATSDR, 2012; McNeill et al., 2012a, b).
1.1.1. General aspects
Chromium (Cr; CAS registry No. 7440-47-3) is widely distributed in the earth’s crust, almost always
in the trivalent chromic state (Cr 3+ or Cr(III); CAS registry 16065-83-1); its concentration is in the
order of few tens of mg/kg in most soils. The metal is produced in large quantities for industrial
purposes, its principal ore being ferrochromite (FeCr 2 O 4 or FeOCr 2 O 3 , in short chromite), in which the
element is present as Cr(III) and iron as Fe 2+ (Fe(II), ferrous state). For incorporation in iron alloys,
chromite is simply reduced with carbon in an electric arc furnace where ferrochrome - also known as
ferrochromium, an alloy of iron and approximately 50-70 % chromium - is concurrently generated:
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