efsa-opinion-chromium-food-drinking-water

Chromium in food and drinking water
annual average concentrations of (total) chromium, particulate Cr, Cr(III), and Cr(VI) were estimated
respectively as 4.6, 2.2, 0.8, and 1.2 nM (0.24, 0.11, 0.042, and 0.062 µg/L). Distinct seasonal and
diurnal variability in the rainwater concentrations of the various chromium species were observed.
Based on the results of a total global flux study, the authors concluded that essentially all chromium
released into the atmosphere is removed via wet deposition and that about half this chromium is
dissolved with similar concentrations of Cr(III) and Cr(VI) forms.
Natural chromium concentrations in seawater were reported to typially range between 0.04 and
0.5 μg/L; in the North Sea, a concentration of 0.7 µg/L was detected (WHO, 2003). The natural total
chromium content of surface waters was reported to be approximately in the range 0.5-2 µg/L while
dissolved chromium concentrations were generally in the range 0.02-0.3 µg/L; chromium
concentrations in Antarctic lakes (range, < 0.6-30 µg/L) appeared to increase as depth increased
(WHO, 2003). In most surface waters, chromium levels were by-and-large between 1 and 10 µg/L, in
general reflecting the impact of industrial activity. In USA rivers and lakes, chromium concentrations
from less than 1 to 30 and below 5 µg/L, respectively, were reported by OEHHA (2011); however, in
U.S. surface waters levels up to 84 µg/L were also detected (WHO, 2003). In the 1960s, chromium
concentrations in the Canadian Great Lakes averaged approximately 1 µg/L (range, < 0.2-19 µg/L),
while concentrations in rivers were found between 2 and 23 µg/L. In central Canada, surface water
concentrations in the period 1980-1985 ranged from less than 2 to 44 µg/L, while for the Atlantic
region the concentrations fell between less than 2 and 24 µg/L (Health Canada, 1986). In the river
Rhine, chromium levels were reported to be below 10 µg/L (WHO, 2003).
Chromium concentrations in groundwater are generally low (< 1 µg/L) (WHO, 2003). In the
Netherlands, a mean concentration of 0.7 µg/L was measured (≤ 5 µg/L). In India, 50 % of
1 473 water samples from dug wells contained less than 2 µg/L. A 1976-1977 survey of Canadian
drinking water supplies suggested that the maximum levels of chromium in unprocessed and treated
waters were up to 14 and 9 (median, 2) µg/L, respectively (Méranger et al., 1979; Health Canada,
1986). Chromium concentrations in water samples taken from a large number of U.S. drinking water
sources in 1974-1975 were on average below 2 µg/L (range 0.4-8.0 µg/L) (DHEW, 1970; WHO,
2003). Over the period 1984-1996, California water monitoring activities detected (total) chromium in
about 9 % of the numerous sources surveyed, with levels up to a maximum of 1100 μg/L (mean,
23 μg/L; median, 17 μg/L) (OEHHA, 2011). In 2001 the California Department of Public Health
(CDPH, then the California Department of Health Services, CDHS) added Cr(VI) to the list of
unregulated chemicals for which monitoring is required (UCMR). Results of 2000-2012 UCMR
monitoring from over 7000 drinking water sources vulnerable to contamination showed Cr(VI) at or
above 1 µg/L (reporting detection limit) in about one-third of them (2432) with the following
distribution breakdown (Cr(VI) concentration range, proportion of detections): 1-10 µg/L, 86.0 %; 11-
20 µg/L, 10.2 %; 21-30 µg/L, 2.7 %; 31-40 µg/L, 0.7 %; 41-50 µg/L, 0.2 %; over 50 µg/L, 0.2 %.
Detections concerned sources and not drinking water served to customers (CDPH, 2013). A Water
Research Foundation project in 2004 surveyed more than 400 drinking water sources (before
treatment) across the USA and found an average Cr(VI) concentration of 1.1 μg/L (median
concentration below the 0.2 μg/L detection limit) (McNeill et al., 2012a, b). Cr(VI) was found in many
drinking water systems by a nationwide survey carried out in 2005-2009 by the U.S. Environmental
Working Group (EWG) (Sutton, 2010). Recently, the U.S. EPA (2010) indicated that for the nearly
186 000 records analysed in public drinking water supplies, 15.3 % of samples had detectable total
chromium concentrations, with a median of 4.2 µg/L and a 90 th percentile of 10 µg/L (min-max
0.009-5200 µg/L). Total dissolved chromium is the parameter most often determined in trace element
analyses of environmental fresh waters and waters for human consumption: however, both the
trivalent and hexavalent forms were shown to exist in surface waters. As water treatment facilities use
strong oxidants to potabilise water, in drinking water chromium may easily be present in the
hexavalent state (Schroeder and Lee, 1975; Health Canada, 1986).
Chromium levels in soils can vary up to three orders of magnitude, reflecting the composition of the
parent rock from which the soils were formed and/or local anthropogenic sources (WHO, 1988, 2000).
In ultramafic (or ultrabasic) and serpentine rocks, chromium (as Cr(III)) may be present at
concentrations in the order of thousands of mg/kg, whereas in granitic rocks and coal the element is on
EFSA Journal 2014;12(3):3595 18