Chromium: The good, the bad, and the not-so-important
Chromium is found and produced in several different forms. The most common forms are metallic, trivalent and hexavalent. The trivalent form occurs naturally and is an essential nutrient. Its needed for fatty acid and cholesterol production and insulin metabolism. It is found in eggs, meat, cheese, whole grains and certain fruits and vegetables. Metallic chromium isn’t pertinent to this article (Pediatric Environmental Health, 3rd edition, Dr. Ruth Etzel, Editor, and Dr. Sophie Balk, Assoc. Editor. Elk Grove Village, IL: 2012).
Hexavalent chromium is the toxic form. The US National Toxicology Program, World Health Organization, EPA, and International Agency for Research on Cancer have all identified hexavalent chromium as a human carcinogen. It comes mostly from industrial emissions and passes into the air, water, and soil. It’s also part of tobacco smoke. Chromium is used in so many ways it isn’t surprising it is found in more than 50% of the National Priorities List superfund hazardous waste sites as well as many landfills. Fossil fuel burning and steel production are major sources of chromium in the air. The movie Erin Brockovich was about The Pacific Gas and Electric Company’s role in the excessive chromium in water and even though it has been out a long time, this is still a real problem.
Absorption of hexavalent chromium from the lungs is high. Gastrointestinal absorption of this form can be as high as 50% but much of it is converted to the trivalent form. Chromium doesn’t stay in the body very long, so antidotes and chelators aren’t in demand. Vitamin C helps convert hexavalent chromium to the trivalent form. Laboratory assessments are not particularly useful, and environmental documentation is more helpful.
Topical chromium is a common cause of allergic contact dermatitis. Swallowing a large amount of hexavalent chromium could cause nausea, vomiting and acute kidney failure.
The biggest concern is with chronic inhalation of the hexavalent form of chromium. Those at highest risk are those working or who have worked in industries where chromium is used. These individuals have an increased chance of developing nasal and lung cancer. The latter risk increases with the duration of an exposure and there’s about a 13 to 30-year latency period. In “Profiling stainless steel welding processes to reduce fume emissions, hexavalent chromium emissions and operating costs in the workplace,” (by M. Keane, et al in Journal of Occupational and Environmental Hygiene, 2016, v. 13#1, pages 1-8) almost half a million Americans do some welding in their work, and that is a potential exposure. Gas metal arc welding was found to create less exposure to toxic gases.
In “Hexavalent Chromium Is Carcinogenic to F344/N Rats and B6C3F1 Mice” (by M. Stout, et al, in Environmental Health Perspectives, v117, #5, for May 2009, pages 716-722), the possibility of an increased risk for oral, stomach and duodenal cancer with chronic consumption of water polluted with excess chromium was raised. The research done involved giving water with various levels of hexavalent chromium in it to the test animals for 2 years. Before you decide that this isn’t relevant to humans, consider the fact that rats and mice are used in research because they share many biological processes and tissue structures with humans.
This all lends support to having water tested, including well water, before even a sip.
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