Chromium toxicity refers to any poisonous toxic effect in an

organism In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multicellular o ...

cell Cell most often refers to: * Cell (biology), the functional basic unit of life Cell may also refer to: Locations * Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...

that results from exposure to specific forms of

chromium Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and h ...

—especially

hexavalent chromium 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). Virtually all chromium ore is processed via hexavalent chromium, specifically the s ...

. Hexavalent chromium and its compounds are toxic when inhaled or ingested.

Trivalent chromium Chromium is a chemical element with the Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium me ...

is a

trace mineral In the context of nutrition, a mineral is a chemical element required as an essential nutrient by organisms to perform functions necessary for life. However, the four major structural elements in the human body by weight (oxygen, hydrogen, carbon, ...

that is essential to human nutrition. There is a hypothetical risk of

genotoxicity Genotoxicity is the property of chemical agents that damage the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, but some genotoxic s ...

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 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). Virtually all chromium ore is processed via hexavalent chromium, specifically the s ...

and

trivalent chromium Chromium is a chemical element with the Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium me ...

are chromium

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by conven ...

s—they have different numbers of

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary partic ...

s 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 Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''hemotoxin'' is to some degree a misnomer since toxins that damage t ...

genotoxic Genotoxicity is the property of chemical agents that damage the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, but some genotoxic sub ...

, and

carcinogenic A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...

. When hexavalent chromium enters the bloodstream, it damages

blood cell A blood cell, also called a hematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), ...

s by causing

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

reactions. This

oxidative damage Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal re ...

can lead to

hemolysis Hemolysis or haemolysis (), also known by several other names, is the rupturing (lysis) of red blood cells (erythrocytes) and the release of their contents (cytoplasm) into surrounding fluid (e.g. blood plasma). Hemolysis may occur in vivo o ...

and, ultimately,

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; bloo ...

and

liver The liver is a major organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the synthesis of proteins and biochemicals necessary for digestion and growth. In humans, it ...

failure. Patients might be treated with

dialysis Dialysis may refer to: *Dialysis (chemistry), a process of separating molecules in solution **Electrodialysis, used to transport salt ions from one solution to another through an ion-exchange membrane under the influence of an applied electric pote ...

. The

median lethal dose In toxicology, the median lethal dose, LD50 (abbreviation for "lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a toxin, radiation, or pathogen. The value of LD50 for a substance is ...

of hexavalent chromium is 50–150 mg/kg. The

World Health Organization The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level o ...

recommends a maximum allowable concentration of 0.05

milligram The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...

s per

litre The litre (international spelling) or liter (American English spelling) (SI symbols L and l, other symbol used: ℓ) is a metric unit of volume. It is equal to 1 cubic decimetre (dm3), 1000 cubic centimetres (cm3) or 0.001 cubic metre (m3 ...

of chromium(VI) in

drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, ...

. In Europe, the use of hexavalent chromium is regulated by the

Restriction of Hazardous Substances Directive The Restriction of Hazardous Substances Directive 2002/95/EC (RoHS 1), short for Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment, was adopted in February 2003 by the European Unio ...

. Hexavalent chromium can be found in some

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution and ...

s and

paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...

s, as well as in some

leather tanning Tanning is the process of treating skins and hides of animals to produce leather. A tannery is the place where the skins are processed. Tanning hide into leather involves a process which permanently alters the protein structure of skin, making ...

products. Primer paint containing hexavalent chromium is widely used in

aerospace Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...

and

automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded ...

refinishing applications. Metal workers (such as welders)—as well as people with a

surgical implant An implant is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. Medical implants are man-made devices, in contrast to a transplant, whi ...

made from cobalt-chromium

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductilit ...

—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 In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the ...

, 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 The Pacific Gas and Electric Company (PG&E) is an American investor-owned utility (IOU). The company is headquartered in the Pacific Gas & Electric Building, in San Francisco, California. PG&E provides natural gas and electricity to 5.2 milli ...

had dumped more than 1.4 billion litres (370 million gallons) of wastewater tainted with hexavalent chromium into the

Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar; es, Desierto de Mojave) is a desert in the rain shadow of the Sierra Nevada mountains in the Southwestern United States. It is named for the indigenous Mojave people. It is located primarily i ...

. This contaminated the groundwater, and caused widespread illness among the people of

Hinkley, California Hinkley is an unincorporated community in the Mojave Desert, in San Bernardino County, California, United States, 14 miles (23 km) northwest of Barstow, 59 miles (95 km) east of Mojave, north of Victorville and about a 120 mile (193 ...

, a small community nearby. As of May 2017, the mandated

environmental remediation Environmental remediation deals with the removal of pollution or contaminants from environmental media such as soil, groundwater, sediment, or surface water. Remedial action is generally subject to an array of regulatory requirements, and may ...

measures are ongoing.

Chromate

Chromates Chromate salts contain the chromate anion, . Dichromate salts contain the dichromate anion, . They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ...

(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 A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...

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 The sulfate or sulphate ion is a polyatomic ion, polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salt (chemistry), ...

and

phosphate In chemistry, a phosphate is an anion, salt, functional group or ester derived from a phosphoric acid. It most commonly means orthophosphate, a derivative of orthophosphoric acid . The phosphate or orthophosphate ion is derived from phosph ...

ions into cells. Contact with products containing chromates can lead to allergic

contact dermatitis Contact dermatitis is a type of acute or chronic inflammation of the skin caused by exposure to chemical or physical agents. Symptoms of contact dermatitis can include itchy or dry skin, a red rash, bumps, blisters, or swelling. These rashes ar ...

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.

Genotoxicity

Hexavalent chromium is

: it damages genetic information in living cells, which results in DNA

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, m ...

s, and possibly the formation of cancerous

tumor A neoplasm () is a type of abnormal and excessive growth of tissue. The process that occurs to form or produce a neoplasm is called neoplasia. The growth of a neoplasm is uncoordinated with that of the normal surrounding tissue, and persists ...

s. One hypothesis asserts that the genotoxicity is caused by

free radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabo ...

s such as

hydroxyl radical The hydroxyl radical is the diatomic molecule . The hydroxyl radical is very stable as a dilute gas, but it decays very rapidly in the condensed phase. It is pervasive in some situations. Most notably the hydroxyl radicals are produced from the ...

s, 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). A third hypothesis proposes that two other forms of chromium—

Chromium(IV) Chromium is a chemical element with the Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal. Chromium me ...

compounds, along with

chromium(V) Chromium is a chemical element with the symbol Cr and atomic number 24. It is the first element in group 6. It is a steely-grey, lustrous, hard, and brittle transition metal. Chromium metal is valued for its high corrosion resistance and hardne ...

produced by

redox reaction Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a de ...

s in the cell—bind to DNA.

Trivalent chromium

, or chromium(III), is an essential

in the human diet. In some

nutritional supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources or that are synthetic in orde ...

s, chromium(III) occurs as

chromium(III) picolinate Chromium(III) picolinate is a chemical compound with the formula Cr(C5H4N(CO2H))3, commonly abbreviated as CrPic3. It is sold as a nutritional supplement to treat type 2 diabetes and promote weight loss. This bright-red coordination compound is de ...

(in which chromium is bound to

picolinic acid Picolinic acid is an organic compound with the formula C5H4N(CO2H). It is a derivative of pyridine with a carboxylic acid (COOH) substituent at the 2-position. It is an isomer of nicotinic acid and isonicotinic acid, which have the carboxyl sid ...

) or

chromium(III) nicotinate Chromium(III) nicotinate is an ionic substance used for chromium supplementation in some nutritional products, where it is also referred to as chromium polynicotinate. It appears in products that are referred to as a medical food used for nutritio ...

(in which chromium is bound to

nicotinic acid Niacin, also known as nicotinic acid, is an organic compound and a form of vitamin B3, an essential human nutrient. It can be manufactured by plants and animals from the amino acid tryptophan. Niacin is obtained in the diet from a variet ...

). Nicotinic acid is also known as the

B vitamin B vitamins are a class of water-soluble vitamins that play important roles in cell metabolism and synthesis of red blood cells. Though these vitamins share similar names (B1, B2, B3, etc.), they are chemically distinct compounds that often coexis ...

niacin Niacin, also known as nicotinic acid, is an organic compound and a form of vitamin B3, an essential human nutrient. It can be manufactured by plants and animals from the amino acid tryptophan. Niacin is obtained in the diet from a variet ...

. Chromium(III) is poorly absorbed in humans; most dietary chromium is excreted in the urine. The threshold for

acute Acute may refer to: Science and technology * Acute angle ** Acute triangle ** Acute, a leaf shape in the glossary of leaf morphology * Acute (medicine), a disease that it is of short duration and of recent onset. ** Acute toxicity, the adverse eff ...

oral toxicity is 1900–3300 mg/kg. In rats,

nonsteroidal anti-inflammatory drug Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...

s such as

aspirin Aspirin, also known as acetylsalicylic acid (ASA), is a nonsteroidal anti-inflammatory drug (NSAID) used to reduce pain, fever, and/or inflammation, and as an antithrombotic. Specific inflammatory conditions which aspirin is used to treat in ...

and

indometacin Indometacin, also known as indomethacin, is a nonsteroidal anti-inflammatory drug (NSAID) commonly used as a prescription medication to reduce fever, pain, stiffness, and swelling from inflammation. It works by inhibiting the production of pros ...

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 Free radical damage to DNA can occur as a result of exposure to ionizing radiation or to radiomimetic compounds. Damage to DNA as a result of free radical attack is called indirect DNA damage because the radicals formed can diffuse throughout th ...

might result.

References

External links

{{Elements in biology Toxic effects of metals