Chromium
Chromium is a naturally occurring metal that can be found in rocks soils and plants. It has various industrial applications and is also used as a dietary supplement. Industrial uses include chrome plating, production of steel and other alloys , additive to limit and prevent corrosion in well drilling mud, wood preservative ad leather tanning . It is also used to make dyes and pigments for paints, as well as making synthetic rubies and emeralds. It named after the Greek word “chroma ” meaning color because it has many colorful compounds.
The Institute of Medicine has developed Reference Daily intakes of chromium at 120 mcg to aid with insulin regulation, weight control and cardiovascular health. However, there are a couple of forms of chromium and not all forms are good for you ; in fact , some may be toxic . The two most common forms are trivalent chromium (Cr Ill) and hexavalent chromium (Cr VI).
Trivalent chromium naturally occurs in several fresh vegetables, fruit, grains and yeast. It is trivalent chromium that has health benefits and is included in dietary supplements.
Hexavalent chromium on the other hand is considered toxic and can cause cancer if it is inhaled . If ingested , hexavalent chromium will be converted it to trivalent upon entering the stomach, but research is ongoing regarding the health effects of hexavalent chromium in our drinking water supplies . There are some studies that seem to indicate ingesting hexavalent chromium causes higher incidence of stomach cancer, so the National Toxicology Program is conducting further studies . The presence of hexavalent chromium typically indicates some type of industrial release or contamination.
How Is It Regulated?
Total chromium is regulated under the Safe Drinking Water Act, with a Maximum Contaminant Level of 0.1 mg/L. This regulation takes into account both trivalent and hexavalent chromium . The World Health Organization (WHO) has a guideline of 0.05 mg/L for total chromium, which takes into account the toxicity of the hexavalent form. California is also in the process of determining an appropriate public health goal specifically for hexavalent chromium and could be set as low as 0.0002 mg/L, but further review is currently being conducted.
Testing For Chromium
You can test for chromium in the field based upon Standard Methods 3500Cr-B . This procedure measures only hexavalent chromium , (Cr6+) . For total chromium determination, acid-digest the sample and follow with a suitable instrumental analysis technique. The hexavalent chromium is determined colorimetrically by reaction with diphenyl carbazide in acid solution . A red-violet colored complex of unknown composition is produced. The reaction is very sensitive.
Laboratories analyzing drinking water samples can utilize various methods including EPA method 200 .7 and 200.8 which utilize an Inductively Coupled Plasma (ICP) or the Standards Method 31138 which uses Graphite Furnace
Water Treatment Options
Chromium imparts no taste or odor in the water, so having the water tested is the only way to determine its presence of total chromium . The EPA has approved the following treatment method for removing chromium : coagulation/filtration, ion exchange , reverse osmosis and lime softening . These treatment methods are intended for water treatment plants. For residential applications the best options are reverse osmosis and distillation.
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