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Acrylamide (or acrylic amide) is an
organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...
with the
chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
CH2=CHC(O)NH2. It is a white odorless solid, soluble in
water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...
and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary amide (CONH2). It is produced industrially mainly as a precursor to polyacrylamides, which find many uses as water-soluble thickeners and flocculation agents. Acrylamide forms in burnt areas of
food Food is any substance consumed by an organism for Nutrient, nutritional support. Food is usually of plant, animal, or Fungus, fungal origin and contains essential nutrients such as carbohydrates, fats, protein (nutrient), proteins, vitamins, ...
, particularly starchy foods like potatoes, when cooked with high heat, above . Despite health scares following this discovery in 2002, and its classification as a probable carcinogen, acrylamide from diet is thought unlikely to cause cancer in humans; Cancer Research UK categorized the idea that eating burnt food causes cancer as a "myth".


Production

Acrylamide can be prepared by the hydration of acrylonitrile, which is catalyzed enzymatically: :CH2=CHCN + H2O → CH2=CHC(O)NH2 This reaction also is catalyzed by
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
as well as various metal salts. Treatment of acrylonitrile with sulfuric acid gives acrylamide sulfate, . This salt can be converted to acrylamide with a base or to methyl acrylate with methanol.


Uses

The majority of acrylamide is used to manufacture various polymers, especially polyacrylamide. This water-soluble polymer, which has very low toxicity, is widely used as thickener and flocculating agent. These functions are valuable in the purification of drinking water, corrosion inhibition, mineral extraction, and paper making. Polyacrylamide gels are routinely used in medicine and biochemistry for purification and assays.


Toxicity and carcinogenicity

Acrylamide can arise in some cooked foods via a series of steps by the reaction of the amino acid asparagine and glucose. This condensation, one of the Maillard reactions, followed by dehydrogenation produces ''N''-(D-glucos-1-yl)-L-asparagine, which upon pyrolysis generates some acrylamide. The discovery in 2002 that some cooked foods contain acrylamide attracted significant attention to its possible biological effects. IARC, NTP, and the EPA have classified it as a probable carcinogen, although epidemiological studies (as of 2019) suggest that dietary acrylamide consumption does not significantly increase people's risk of developing
cancer Cancer is a group of diseases involving Cell growth#Disorders, abnormal cell growth with the potential to Invasion (cancer), invade or Metastasis, spread to other parts of the body. These contrast with benign tumors, which do not spread. Po ...
.


Europe

According to the EFSA, the main toxicity risks of acrylamide are " Neurotoxicity, adverse effects on male reproduction, developmental toxicity and carcinogenicity". However, according to their research, there is no concern on non- neoplastic effects. Furthermore, while the relation between consumption of acrylamide and cancer in rats and mice has been shown, it is still unclear whether acrylamide consumption has an effect on the risk of developing cancer in humans, and existing epidemiological studies in humans are very limited and do not show any relation between acrylamide and cancer in humans. Food industry workers exposed to twice the average level of acrylamide do not exhibit higher cancer rates.


United States

Acrylamide is classified as an extremely hazardous substance in the United States as defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. 11002), and is subject to strict reporting requirements by facilities which produce, store, or use it in significant quantities. Acrylamide is considered a potential occupational carcinogen by U.S. government agencies and classified as a Group 2A carcinogen by the IARC. The Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have set dermal occupational exposure limits at 0.03 mg/m3 over an eight-hour workday.


Opinions of health organizations

Baking, grilling or broiling food causes significant concentrations of acrylamide. This discovery in 2002 led to international health concerns. Subsequent research has however found that it is not likely that the acrylamides in burnt or well-cooked food cause cancer in humans; Cancer Research UK categorizes the idea that burnt food causes cancer as a "myth". The American Cancer Society says that laboratory studies have shown that acrylamide is likely to be a carcinogen, but that evidence from epidemiological studies suggests that dietary acrylamide is unlikely to raise the risk of people developing most common types of cancer.


Hazards

Radiolabeled acrylamide is also a skin irritant and may be a tumor initiator in the skin, potentially increasing risk for skin cancer. Symptoms of acrylamide exposure include dermatitis in the exposed area, and peripheral neuropathy. Laboratory research has found that some phytochemicals may have the potential to be developed into drugs which could alleviate the toxicity of acrylamide.


Mechanism of action

left, Glycidamide is the dangerous metabolite produced from acrylamide, which in turn is produced by heating certain proteins. Acrylamide is metabolized to the genotoxic derivative glycidamide. On the other hand, acrylamide and glycidamide can be detoxified via conjugation with glutathione.


Occurrence in food

Acrylamide was discovered in foods, mainly in starchy foods, such as potato chips (UK: ''potato crisps''), French fries (UK: ''chips''), and bread that had been heated higher than . Production of acrylamide in the heating process was shown to be temperature-dependent. It was not found in food that had been boiled, or in foods that were not heated. Acrylamide has been found in roasted barley tea, called ''mugicha'' in Japanese. The
barley Barley (), a member of the grass family, is a major cereal grain grown in temperate climates globally. It was one of the first cultivated grains; it was domesticated in the Fertile Crescent around 9000 BC, giving it nonshattering spikele ...
is roasted so it is dark brown prior to being steeped in hot water. The roasting process produced 200–600 micrograms/kg of acrylamide in mugicha. This is less than the >1000 micrograms/kg found in potato crisps and other fried whole potato snack foods cited in the same study and it is unclear how much of this enters the drink to be ingested. Rice cracker and sweet potato levels were lower than in potatoes. Potatoes cooked whole were found to have significantly lower acrylamide levels than the others, suggesting a link between food preparation method and acrylamide levels. Acrylamide levels appear to rise as food is heated for longer periods of time. Although researchers are still unsure of the precise mechanisms by which acrylamide forms in foods, many believe it is a byproduct of the Maillard reaction. In fried or baked goods, acrylamide may be produced by the reaction between asparagine and reducing sugars (
fructose Fructose (), or fruit sugar, is a Ketose, ketonic monosaccharide, simple sugar found in many plants, where it is often bonded to glucose to form the disaccharide sucrose. It is one of the three dietary monosaccharides, along with glucose and gal ...
,
glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecular formula , which is often abbreviated as Glc. It is overall the most abundant monosaccharide, a subcategory of carbohydrates. It is mainly made by plants and most algae d ...
, etc.) or reactive carbonyls at temperatures above . Later studies have found acrylamide in black olives, dried plums, dried pears, coffee, and
peanut The peanut (''Arachis hypogaea''), also known as the groundnut, goober (US), goober pea, pindar (US) or monkey nut (UK), is a legume crop grown mainly for its edible seeds. It is widely grown in the tropics and subtropics by small and large ...
s. The US FDA has analyzed a variety of U.S. food products for levels of acrylamide since 2002.


Occurrence in cigarettes

Cigarette smoking is a major acrylamide source. It has been shown in one study to cause an increase in blood acrylamide levels three-fold greater than any dietary factor.


See also

* Acrydite: research on this compound casts light on acrylamide * Acrolein * Alkyl nitrites * Deep-frying * Deep fryer * Vacuum fryer * Substance of very high concern * Heterocyclic amines * Polycyclic aromatic hydrocarbons


References


Further reading

*


External links

{{Authority control Carboxamides IARC Group 2A carcinogens Monomers Reproductive toxicants Suspected fetotoxicants