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Introduction
Approximately 170,000 tonnes of chromium (Cr) are released annually to the environment
through a large number of industrial activities such as steelworks, petroleum refining, metal
finishing, Cr electroplating, leather tanning, etc. The uncontrolled or accidental release of Cr
wastes has in many cases caused serious contamination of surface water and groundwater
bodies. In the environment, Cr is usually encountered in the oxidation states of Cr(III) and
Cr(VI). Each of the above oxidation states has very different biological and chemical properties.
Trivalent Cr is more stable, nearly immobile and has relatively low toxicity. Conversely
hexavalent Cr is very soluble and thus highly mobile in the environment and presents high
toxicity, being acutely toxic, mutagenic, teratogenic and carcinogenic.
Until recently, high levels of hexavalent Cr in the environment were attributed as a rule to
anthropogenic pollution. However over the last 5 - 10 years there are reports in the literature
demonstrating that relatively high levels of hexavalent Cr may be due to natural geogenic
processes, especially in areas where there are relatively high levels of naturally occurring Cr(III)
or Cr (VI) in the sediments, and natural processes that can convert Cr(III) to Cr(VI). Such
conditions are met in several populated areas in the Pacific (California (USA), Mexico) and in
the Mediterranean (Greece, Italy) as well as in other parts of the world. According to these
findings in ultramafic rocks and serpentinites of ophiolite complexes, Cr content may exceed
values of 200 mg/L. These values are much higher than these of limestones (22 mg/L) and
sandstones (35 mg/L). Although chromite [FeCr(III)2O4} which is the primary form of Cr in
ultramafic rocks, exhibits very low solubility in water, there are some naturally occurring oxidants
of Cr(III), i.e. some Fe(III) and Mn(IV) compounds which can oxidize Cr(III) to Cr(VI) at pH less
than 9.
The aim of this report, is to present the aspects of chromium related to its presence in the
aquatic environment, namely:

2. 1. International legal framework regarding the presence of chromium and its forms, related
to different water uses and environmental quality standards (Chapter 2)
2. Information on its origin (Chapter 3)
Its fate when discharged into the environment and its impact on the aquatic
environment which may be related to toxicity, dispersion tendency, persistence and
bioaccumulation (Chapter 4)
3. A concluding chapter that summarises the key points of the report is included (Chapter
5).
LEGAL FRAMEWORK REGARDING THE PRESENCE OF CHROMIUM
AND HEXAVALENT CHROMIUM IN WATER
Chromium can be found in various oxidation states most importantly as CrIII and
CrVI. Cr III, the most abundant environmental form, is an essential element that plays a
role in glucose metabolism. Chromium deficiency causes changes in the metabolism
of glucose and lipids and may be associated with a number of disorders (Anderson,
1993, 1995). Several recommendations for daily oral intakes of chromium have been
reported, an indicative number of them presented in Figure 1.