Chromium toxicity refers to any poisonous toxic effect in an organism or cell that results from exposure to specific forms of chromium—especially hexavalent chromium. Hexavalent chromium and its compounds are toxic when inhaled or ingested. Trivalent chromium is a trace mineral that is essential to human nutrition. There is a hypothetical risk of genotoxicity in humans if large amounts of trivalent chromium were somehow able to enter living cells, but normal metabolism and cell function prevent this.
Forms of chromium
Hexavalent chromium and trivalent chromium are chromium ions—they have different numbers of electrons and, therefore, different properties. Trivalent chromium, or chromium(III), is the form of chromium that is essential to human health. Hexavalent chromium, or chromium(VI), is an unequivocally toxic form.
Hexavalent chromium, also called chromium(VI), is hemotoxic, genotoxic, and carcinogenic. When hexavalent chromium enters the bloodstream, it damages blood cells by causing oxidation reactions. This oxidative damage can lead to hemolysis and, ultimately, kidney and liver failure. Patients might be treated with dialysis.
The median lethal dose of hexavalent chromium is 50–150 mg/kg. The World Health Organization recommends a maximum allowable concentration of 0.05 milligrams per litre of chromium(VI) in drinking water. In Europe, the use of hexavalent chromium is regulated by the Restriction of Hazardous Substances Directive.
Hexavalent chromium can be found in some dyes and paints, as well as in some leather tanning products. Primer paint containing hexavalent chromium is widely used in aerospace and automobile refinishing applications. Metal workers (such as welders)—as well as people with a surgical implant made from cobalt-chromium alloy—may also be exposed to hexavalent chromium. Chromium concentrations in whole blood, plasma, serum, or urine may be measured to monitor for safety in exposed workers, to confirm the diagnosis in potential poisoning victims, or to assist in the forensic investigation in a case of fatal overdosage.
In the U.S. state of California, an epidemic of hexavalent chromium exposure led to a class-action lawsuit in 1993: Anderson, et al. v. Pacific Gas and Electric. The Pacific Gas and Electric Company had dumped more than 1.4 billion litres (370 million gallons) of wastewater tainted with hexavalent chromium into the Mojave Desert. This contaminated the groundwater, and caused widespread illness among the people of Hinkley, California, a small community nearby. As of May 2017, the mandated environmental remediation measures are ongoing.
Chromates (chromium salts) formed from hexavalent chromium are used to manufacture leather products, paints, cement, mortar, anti-corrosives, and other things. They are carcinogenic and allergenic. The carcinogenity of chromate dust has been documented since the late 19th century, when workers in a chromate dye company were found to exhibit high incidence of cancer. Chromate enters cells by means of the same transport mechanism that carries sulfate and phosphate ions into cells.
Contact with products containing chromates can lead to allergic contact dermatitis and irritant dermatitis, resulting in ulceration of the skin—a condition sometimes called chrome ulcers. Workers that have been exposed to strong chromate solutions in electroplating, tanning, and chrome-producing manufacturers may also develop chrome ulcers.
This section needs to be updated.(June 2018)
Hexavalent chromium is genotoxic: it damages genetic information in living cells, which results in DNA mutations, and possibly the formation of cancerous tumors. One hypothesis asserts that the genotoxicity is caused by free radicals such as hydroxyl radicals, produced by the reduction of chromium(VI) to chromium(III). Another proposed mechanism supposes that chromium binds to DNA at the end of the reduction to chromium(III).
Trivalent chromium, or chromium(III), is an essential trace mineral in the human diet. In some nutritional supplements, chromium(III) occurs as chromium(III) picolinate (in which chromium is bound to picolinic acid) or chromium(III) nicotinate (in which chromium is bound to nicotinic acid). Nicotinic acid is also known as the B vitamin niacin.
Chromium(III) is poorly absorbed in humans; most dietary chromium is excreted in the urine. The threshold for acute oral toxicity is 1900–3300 mg/kg. In rats, nonsteroidal anti-inflammatory drugs such as aspirin and indometacin can increase chromium absorption.
Ordinarily, cellular transport mechanisms in humans and some other animals limit the amount of chromium(III) that enters a cell. Hypothetically, if an excessive amount was able to enter a cell, free radical damage to DNA might result.
- Bogden, John D.; Klevay, Leslie M., eds. (2000). "Trace Elements and Minerals in the Elderly § Chromium". Clinical Nutrition of the Essential Trace Elements and Minerals: The Guide for Health Professionals. Springer Science+Business Media. p. 189. ISBN 978-1-61737-090-8 – via Google Books.
- Barceloux, Donald G.; Barceloux, Donald (1999). "Chromium". Clinical Toxicology. 37 (2): 173–194. doi:10.1081/CLT-100102418. PMID 10382554.
- Dayan, A. D.; Paine, A. J. (2001). "Mechanisms of chromium toxicity, carcinogenicity and allergenicity: Review of the literature from 1985 to 2000". Human & Experimental Toxicology. 20 (9): 439–451. doi:10.1191/096032701682693062. PMID 11776406. S2CID 31351037.
- Katz, Sidney A.; Salem, H (1992). "The toxicology of chromium with respect to its chemical speciation: A review". Journal of Applied Toxicology. 13 (3): 217–224. doi:10.1002/jat.2550130314. PMID 8326093. S2CID 31117557.
- "WHO Guidelines on Drinking-Water Quality" (PDF). WHO.int. World Health Organisation. Section 12.30: Chromium.
- Merritt, Katharine; Brown, Stanley A. (May 1995). "Release of hexavalent chromium from corrosion of stainless steel and cobalt—chromium alloys". Journal of Biomedical Materials Research. 29 (5): 627–633. doi:10.1002/jbm.820290510. PMID 7622548.
- Baselt, R. (2008). Disposition of Toxic Drugs and Chemicals in Man (8th ed.). Foster City: Biomedical Publications. pp. 305–7. ISBN 978-0962652370.
- Izbicki, John A.; Groover, Krishangi. "Natural and Man-Made Hexavalent Chromium, Cr(VI), in Groundwater near a Mapped Plume, Hinkley, California—Study Progress as of May 2017, and a Summative-Scale Approach to Estimate Background Cr(VI) Concentrations" (PDF). Open-file Report. United States Geological Survey. ISSN 2331-1258. Retrieved 2018-05-15.
- Newman, D. (1890). "A case of adeno-carcinoma of the left inferior turbinated body, and perforation of the nasal septum, in the person of a worker in chrome pigments". Glasgow Medical Journal. 33: 469–470.
- Langard, Sverre (1990). "One Hundred Years of Chromium and Cancer: A Review of Epidemiological Evidence and Selected Case Reports". American Journal of Industrial Medicine. 17 (2): 189–215. doi:10.1002/ajim.4700170205. PMID 2405656.
- "Chrome Contact Allergy". DermNet NZ.
- Basketter, David; Horev, L.; Slodovnik, D.; Merimes, S.; Trattner, A.; Ingber, A. (2000). "Investigation of the threshold for allergic reactivity to chromium". Contact Dermatitis. 44 (2): 70–74. doi:10.1034/j.1600-0536.2001.440202.x. PMID 11205406. S2CID 45426346.
- Basketter, D. A.; Briatico-Vangosa, G.; Kaestner, W.; Lally, C.; Bontinck, W. J. (1992). "Nickel, cobalt and chromium in consumer products: A role in allergic contact dermatitis?". Contact Dermatitis. 28 (1): 15–25. doi:10.1111/j.1600-0536.1993.tb03318.x. PMID 8428439. S2CID 35966310.
- M. D., Cohen; Kargacin, B.; Klein, C. B.; Costa, M. (1993). "Mechanisms of chromium carcinogenicity and toxicity". Critical Reviews in Toxicology. 23 (3): 255–81. doi:10.3109/10408449309105012. PMID 8260068.
- Javed, Kashif; Amjad, Muhammad; Ashraf, Yasmin; Saddiqa, Aisha; Ashraf, Samina; Waqas, Muhammad; Naseer, Sumra; Hussain, Shabbir (2020). "Factors Affecting the Rate of Breast Cancer; Role of Heavy Metals". International Journal of Economic and Environmental Geology. 11 (3): 57–64. doi:10.46660/ijeeg.Vol11.Iss3.2020.476. S2CID 230634595.
- "Chromium § Toxicity". Micronutrient Information Center. Oregon State University. 22 April 2014. Retrieved 2018-04-15.
- "Chromium § Drug interactions". Micronutrient Information Center. Oregon State University. 22 April 2014. Retrieved 2018-04-15.
- Eastmond, David A.; MacGregor, JT; Slesinski, RS (2008). "Trivalent Chromium: Assessing the Genotoxic Risk of an Essential Trace Element and Widely Used Human and Animal Nutritional Supplement". Critical Reviews in Toxicology. 38 (3): 173–190. doi:10.1080/10408440701845401. PMID 18324515. S2CID 21033504.