Chromium was discovered in 1798, compounds of which can take many different colours - indeed its name derives from the Greek word chroma meaning colour. Chromium has many uses, such as being alloyed with steel to create the corrosion resistant stainless steel. Chromium plating is widely used to provide a shiny, corrosion resistant finish to car parts and to the household fittings used in kitchens and bathrooms.
Chromium compounds have long been used in the production of leather and are regarded as the most efficient tanning agents. Compounds of chromium are used in industry as catalysts and as pigments. Compounds can be bright green, yellow, and red and have applications in paints. For example the characteristic yellow school buses of the US are coloured with Chrome Yellow (lead chromate). The green colour of emeralds is created by chromium as is the red colour of rubies.
Chromium can exist in many different forms that are termed valences or oxidation states. Aside from the elemental chromium trace metal, the two main forms of chromium are trivalent chromium (Cr3+ or Cr III) and hexavalent chromium (Cr6+ or Cr VI). Whilst trivalent chromium is thought to play a role in insulin metabolism, hexavalent chromium is highly toxic and is classified as a human carcinogen.
Opinion is divided as to whether trivalent chromium should be classed as an essential micronutrient for the human body with the USA concluding that chromium is essential and the EU that it is not. It has been proposed that trivalent chromium can act as a cofactor for biologically active molecules that effect how insulin binds to its target receptors. Chromium picolinate, a compound of trivalent chromium, has been proposed as a dietary supplement to promote weight loss, the evidence for such effect is deemed uncertain/unreliable and the European Food Safety Authority has concluded that there is insufficient evidence to support any weight loss claim.
Hexavalent chromium is a recognised carcinogen, exposure to which in dust has been associated with increased incidences of lung cancer and cancers of the nose and nasal sinuses. Ingestion of hexavalent chromium through our drinking water has been found to produce cancers in the oral cavity and small intestine. Hexavalent chromium is also absorbed from soil by the tabacco plant and is a constituent of tobacco smoke.
As chromium has been widely used in a number of industrial applications, not least dyes, paints, and leather tanning compounds, it is often found as a contaminant of soil and groundwater. Primer paints containing hexavalent chromium are still widely used in aerospace and automobile industries.
In 2011 an incident at a chemical factory in New South Wales, Australia, led to the release of 200 kg of highly toxic hexavalent chromium into the environment. The nearby town was not notified until three days after the accident, sparking a major public controversy.
Legal clerk and consumer advocate Erin Brockovich brough a case against the Pacific Gas and Electric Company for the alleged contamination of drinking water with hexavalent chromium in the southern Californian town of Hinkley. The case was settled for $333m and was later popularised in the 2000 film starring Julia Roberts.
Chromium in your drinking water can be detected by the following tests.
Chromium can be reduced or removed from your drinking water using the following methods.
