Hexavalent chromium, or Cr(VI) is a metal compound used in various manufacturing industries. Exposure to high levels of hexavalent chromium is linked to a wide array of health problems, including some forms of cancer. The Environmental Protection Agency, or EPA, limits allowable levels in the workplace and in groundwater.
Forms of Chromium
The element chromium occurs in three major forms. Metallic chromium or Cr(0) does not occur naturally, but is produced from chrome ore and is used in making steel. Naturally occurring chromium, called trivalent chromium or Cr(III), is found in rocks, soil, plants and animals and is an essential nutrient for humans. When heated with mineral bases, Cr(III) turns into hexavalent chromium, or Cr(VI).
Uses
Hexavalent chromium has a variety of industrial uses. Its anti-corrosive properties make it an efficient liner for industrial wastewater cooling tanks. It is also used in metal finishing, manufacture of stainless steel and textiles, wood preservation and leather tanning. Lead chromate paint provides the brilliant yellow of road markings, but these pigments may not be used in consumer goods or products that might be used by or around children because of the health dangers of exposure to hexavalent chromium.
Exposure
Exposure to hexavalent chromium occurs through contaminated air, dust, water or food. The toxin can be inhaled or ingested. Most exposure occurs in workplaces where the compound is used, but workers can bring significant concentrations home on their clothes, and industrial waste can seep into the groundwater or soil around manufacturing sites or dumping grounds.
Levels
The September 2000 issue of "Environmental Health Perspectives" cites figures of acceptable and actual measured levels of total chromium -- Cr(0), Cr(III) and Cr(VI) -- and Cr(VI) only in the environment. Urban air contains about 0.01 to 0.03 micrograms (µg)/m3 of total chromium. The EPA recommends exposure of no more than 1 µg/m3 of hexavalent chromium, but the permissible level is higher, 100 µg/m3. However, in chrome plating sites, levels can climb as high as 120 µg/m3, and welding fumes can have up to 1,500 µg/m3.
Health Risks
Exposure to as little as 2 µg/m3 of hexavalent chromium in the air can cause sneezing and irritate the nasal passages. At higher concentrations, it causes nasal ulcers, perforations of the septum, and even nasal and lung cancer. Ingesting hexavalent chromium is associated with kidney and liver damage, stomach ulcers, convulsions or death. Studies in mice show that ingesting hexavalent chromium can also cause cancer (CE-NIEHS press release).
Cr(VI) and Hollywood
The Academy Award-winning movie "Erin Brockovich" tells the story of the residents of Hinckley, Calif. and their legal battle with Pacific Gas and Electric, accused of poisoning the town's groundwater with hexavalent chromium at levels more than 10 times the state's limit. As a result of the lawsuit launched through the efforts of legal assistant Erin Brockovich, PG&E was forced to clean up the contamination and pay medical settlements amounting to over $333 million (CE- Envi Health Pers) to 648 residents of Hinckley suffering from the effects of hexavalent chromium exposure.
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