Chromium hexavalent compounds
Chromium hexavalent compounds, also known as hexavalent chromium or chromium (VI), are highly oxidized forms of the element chromium, characterized by their combination with six oxygen atoms. These compounds are widely used in various industrial applications, including chromate dyes, anticorrosive agents in paints, and leather-tanning products. However, they pose significant health risks, as they are classified as known human carcinogens, particularly associated with lung cancer, and, less commonly, cancers of the nose and sinuses.
Exposure to chromium hexavalent compounds primarily occurs through inhalation, but can also result from skin contact and ingestion of contaminated water. Workers in industries that handle these compounds are at the highest risk, along with individuals living near contaminated sites or using products containing hexavalent chromium. The health impacts of exposure can range from respiratory issues, such as coughing and bronchitis, to severe conditions that may lead to cancer.
The history of chromium dates back to the late 18th century when it was first utilized as a pigment, but its carcinogenic properties were not recognized until 1980. Since then, regulations have tightened, with organizations such as OSHA enforcing exposure limits, and states like California setting standards for chromium levels in drinking water. Ongoing research continues to investigate the link between these compounds and cancer, highlighting the importance of awareness and safety measures in environments where exposure can occur.
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Subject Terms
Chromium hexavalent compounds
ROC STATUS: Known human carcinogen since 1980
ALSO KNOWN AS: Hexavalent chromium, chromium 6, chromium (VI), Cr (VI)
RELATED CANCERS: Lung cancer, and less commonly, cancers of the nose and sinuses
DEFINITION: The term “hexavalent” describes how highly oxidized chromium becomes in a chemical compound, and it means that the element chromium has combined with six oxygen atoms. This fully oxygenated form is associated with chromium’s most significant industrial use and serious health concerns.
Exposure routes: Primarily inhalation and, to a lesser extent, skin contact and water intake
Where found: Chromate dyes of plastics, inks, and photographic processing compounds; anticorrosive agent in paints, electroplated metal, and welded stainless steel; and in leather-tanning products, textile dyes, and wood preservatives
At risk: Workers in daily contact with hexavalent chromium. There is also concern among people living near contaminated wastewater, people who breathe air polluted with chromium hexavalent compounds, and those who have skin contact with products containing these compounds. Hexavalent chromium became part of the American lexicon following the film Erin Brockovich (2000), a true-life cautionary tale about a cancer cluster seemingly associated with local drinking water industrial contamination. The National Toxicology Program reported in 2011 that in 2007, over 1,100 sites were responsible for releasing fifty-one million pounds of chromium compounds. In 2022, over 1,000 sites in the United States were still producing chromium hexavalent compounds. The health risk from this discharge is impossible to quantify, but it is very real and dangerous.
Etiology and symptoms of associated cancers: The respiratory tract is the most common site for hexavalent chromium damage. This damage may lead to septal ulceration and perforation, bronchitis, asthma, pneumonia, decreased lung function, and cancers of the nose, nasal sinus cavities, and lungs. Even short-term exposure may manifest in fits of coughing, wheezing, and shortness of breath. Although the respiratory tract is the primary area of concern, injury to the kidneys, liver, teeth, eardrums, eyes, and skin is possible. Although genetic damage following hexavalent chromium exposure is clear, and some findings have indicated that epigenetics may play a role, research has not yet fully described the exact cellular mechanism that results in cancer. However, it is believed that after chromium hexavalent compounds enter a cell, they produce free oxygen radicals which cause lipid peroxidation, cell membrane alterations, enzyme inhibition, and DNA damage.
History: Shortly after chromium, “the red mineral,” was found in Siberia toward the end of the eighteenth century, it became useful as a paint pigment and leather-tanning product. Although some of its health risks soon became apparent, it was not until 1980 that the US government officially acknowledged its role as a carcinogen. In the twenty-first century, businesses using hexavalent chromium must establish the exposure rates of their workers. The Occupational Safety and Health Administration (OSHA) has played a crucial role, mandating strict monitoring and eight-hour exposure limits to hexavalent chromium dust or fumes in targeted job sites.
In 2024, California became the first state to set standards for levels of chromium hexavalent compounds in drinking water in an effort to reduce its carcinogenic effects. Additionally, in California, concern was raised over the amount of exposure to chromium hexavalent compounds during the state’s increasingly active wildfire season. Finally, ongoing research by the National Toxicology Program shows a clear correlation between oral exposure to chromium hexavalent compounds and cancer in laboratory trials using animals.
Bibliography
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