Context: The National Green Tribunal has instructed the Central Ground Water Board (CGWB) to investigate chromium contamination in the groundwater of Sukinda Valley, Odisha.
Key Details:
- Location: Sukinda Valley in Odisha is home to 97% of India’s chromite ore deposits.
- Chromium Characteristics: Chromium is a shiny, hard, brittle metal with a silver-grey color, found naturally in rocks, plants, soil, volcanic dust, and animals, but not in its free metal form. It is primarily extracted as the mineral chromite.
- Common Forms in Water:
- Trivalent Chromium (Cr III): A necessary dietary element found in many foods like vegetables, fruits, meats, grains, and yeast.
- Hexavalent Chromium (Cr VI): Toxic and classified by the WHO as carcinogenic, it can cause severe health issues including stomach ulcers, cancers, and significant damage to the kidneys and liver.
Properties:
- Oxidation: Chromium does not tarnish in air and forms a protective green chromic oxide layer when heated.
- Stability: In oxygen, it forms a thin oxide layer that protects the underlying metal.
Applications:
- Aesthetics and Protection: Used for its shiny appearance to coat cars, stoves, and other appliances, protecting them from corrosion.
- Industrial Uses: Its high melting point and stability make it valuable in the textile and refractory industries.
- Alloys and Plating: Integral in stainless steel production, chrome plating, and metal ceramics.
- Catalytic Uses: Employed as a catalyst in dyeing, leather tanning, and making molds for brick firing.
- Magnetic Tape Production: Chromium (IV) oxide (CrO2) is used in manufacturing magnetic tape.
Chromium Pollution:
- Permissible Limits:
- Indian Standards: The maximum permissible concentration of hexavalent chromium (Cr VI) in drinking water is 50 micrograms per liter.
- US EPA Standards: The recommended permissible concentration is lower, at 10 micrograms per liter.