efsa-opinion-chromium-food-drinking-water

Chromium in food and drinking water
Outside Europe, the mean concentrations are also generally well below 2 µg/L, except in three studies
(in Egypt, Nigeria and Japan) where the mean concentrations found are largely higher (range
17-110 µg/L; Carter et al., 1968; Okolo et al., 2001; Yamawaki et al., 2005). However, in the more
recent Japan study (Yoshida et al., 2008), the mean concentration found were also below 2 µg/L and
according to the authors, the results of the Yamawaki et al. (2005) study were not reliable, since no
evaluation of analytical values using standard reference materials was performed. It is likely that the
high levels observed in the other studies are also related to analytical bias poorly mastered by adequate
internal quality controls. Recently, Sola-Larrañaga and Navarro-Blasco (2006) reported a range of
chromium concentration in human milk of 0.20-8.18 µg/L.
4.1.4. Total chromium and/or hexavalent chromium in drinking water
Examples of chromium occurrence in drinking water are reported hereafter from the reviews of WHO
(2003) and McNeill et al. (2012a,b), while a summary of chromium in environmental water and
drinking water sources is available in Chapter 1. Approximately 18 % of the population of the USA in
1987 were exposed to drinking water total Cr levels between 2 and 60 μg/L and < 0.1 % to levels
between 60 and 120 μg/L. Cr(VI) was measured in the tap water of 31 out of 35 cities sampled -
several of which have a population greater than 1 million - at concentrations in the range
0.03-12.9 µg/L. Therefore, in most cities drinking water was found to exceed California’s 2011 Public
Health Goal (0.02 µg/L) (OEHHA, 2011). On the whole, eight, 15, and eight of the cities tested by the
EWG were found to have drinking water with Cr(VI) oncentrations respectively above 1, between
0.1 and 1, and below 0.1 µg/L.
Out of the 138 445 results on total chromium extracted from the French SISE-EAUX (Health and
Environment Information System on Water) database for the period 1 January 2001 to 31 March 2011,
133 191 (96.2 %) are below the LOQ (ranging from 1 to 10 µg/L, median LOQ of 5 µg/L and average
LOQ of 4 µg/L) and 14 cases of non-compliance in total Cr were reported, ranging from 51 to
199 μg/L, with a median of 63 μg/L (ANSES, 2012).
4.1.5. Conclusions
Staple foods are particularly low in total chromium. Processed meats, whole grain products, pulses and
spices are the main sources of chromium, whilst dairy products and most fruit and vegetables, contain
only small amounts. Scarce studies have analysed the chromium speciation in some food samples
(milk, mushrooms, bread, tea) and concluded that the percentage of Cr(VI) relative to total Cr is, in
average, generally below 10 % (range 1.31-12.9 %). However, Novotnik et al. (2013) showed the
absence of Cr(VI) in bread and tea samples using a more accurate and precise speciation method (a
speciated isotopic dilution technique to follow Cr(VI) and Cr(III) species interconversion during the
extraction procedure). These results indicated that previous Cr(VI) findings were probably due to
analytical artefacts. The assumption that Cr(III) cannot be oxidised to Cr(VI) when baking or toasting
bread, because of the reductive nature of the organic substances of the flour, was also reported by
Kovacs et al. (2007). According to Novotnik et al. (2013), the data confirmed that Cr(VI) does not
exist in foodstuffs of plant origin and provided some conclusive evidence that the same can be
expected for foods of animal origin.
Cold and hot common beverages, such as coffee, tea, orange juice, etc., were investigated as potential
electron donors in the reduction of Cr(VI) to Cr(III) (see, for instance: Kerger et al., 1996; Kim et al.,
2012). Laboratory studies were carried out under conditions mimicking real situations, with excess
reduction capacities of the beverages. According to Kerger et al. (1996), the reduction process would
be thermodynamically favoured and, given enough time, all Cr(VI) would turn into Cr(III). However,
the experimental rates of reaction presented a remarkable variability: from very fast (disappearance of
Cr(VI) in few minutes) to quite slow, with a partial survival of Cr(VI) species for hours. Apparently,
there were no reliable indications to predict how Cr(VI), if present, would behave as a function of
time. In the relatively complex matrices tested, the redox reaction kinetics depended on a considerable
array of factors, largely unknown or uncharacterized. In the end, the aforesaid papers demonstrated
that Cr(VI) in certain beverages may undergo a complete fast reduction to Cr(III), whereas in other
cases a fraction of Cr(VI) may survive long enough for a potential uptake. Nothing well-founded can
EFSA Journal 2014;12(3):3595 35