![]() ![]() Yet, soluble chromates are a confirmed carcinogen so it would be prudent to consider all chromates carcinogenic. īoth insoluble salts of lead and barium chromates as well as soluble chromates were negative in the implantation model of lung carcinogenesis. According to Shi et al., the DNA can also be damaged by hydroxyl radicals produced during reoxidation of pentavalent chromium by hydrogen peroxide molecules present in the cell, which can cause double-strand breakage. This causes strand breaks and Cr–DNA adducts which are responsible for mutagenic damage. The resultant chromium(III) forms stable complexes with nucleic acids and proteins. Vitamin C and other reducing agents combine with chromate to give chromium(III) products inside the cell. The reduction occurs via direct electron transfer primarily from ascorbate and some nonprotein thiols. Inside the cell, hexavalent chromium(VI) is reduced first to pentavalent chromium(V) then to trivalent chromium(III) without the aid of any enzymes. Due to its structural similarity to sulfate, chromate (a typical form of chromium(VI) at neutral pH) is transported into cells via sulfate channels. Hexavalent chromium compounds are genotoxic carcinogens. Within the European Union, the use of hexavalent chromium in electronic equipment is largely prohibited by the Restriction of Hazardous Substances Directive and the European Union regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals. Workers who are exposed to hexavalent chromium are at increased risk of developing lung cancer, asthma, or damage to the nasal epithelia and skin. Problematic exposure is known to occur among workers who handle chromate-containing products and those who grind and/ or weld stainless steel. Workers in many occupations are exposed to hexavalent chromium. Positive associations have also been observed between exposure to chromium (VI) compounds and cancer of the nose and nasal sinuses. Īll hexavalent chromium compounds are toxic (due to their oxidizing power) as well as carcinogenic ( IARC Group 1), especially if airborne and inhaled where they cause lung cancer. Hexavalent chromium can also be found in drinking water and public water systems. In these situations the chromium is not originally hexavalent, but the high temperatures involved in the process result in oxidation that converts the chromium to a hexavalent state. ![]() Hexavalent chromium can be formed when performing "hot work" such as welding on stainless steel or melting chromium metal. Industrial uses of hexavalent chromium compounds include chromate pigments in dyes, paints, inks, and plastics chromates added as anticorrosive agents to paints, primers, and other surface coatings and chromic acid electroplated onto metal parts to provide a decorative or protective coating. Hexavalent chromium is used in textile dyes, wood preservation, anti-corrosion products, chromate conversion coatings, and a variety of niche uses. Īdditional hexavalent chromium compounds include chromium trioxide and various salts of chromate and dichromate, among others. Approximately 136,000 tonnes (150,000 tons) of hexavalent chromium were produced in 1985. ![]() Hexavalent chromium is key to all materials made from chromium. Virtually all chromium ore is processed via hexavalent chromium, specifically the salt sodium dichromate. Hexavalent chromium ( chromium(VI), Cr(VI), chromium 6) is chromium in any chemical compound that contains the element in the +6 oxidation state (thus hexavalent). Chromium in the +6 oxidation state An example of a chromium(VI) compound: chromium trioxide ![]()
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