HOME

TheInfoList



OR:

A carcinogen is any substance,
radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
, or radiation that promotes
carcinogenesis Carcinogenesis, also called oncogenesis or tumorigenesis, is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, and epigenetic levels and abnor ...
(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 substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example gamma rays and
alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay, but may also be produce ...
s, which they emit. Common examples of non-radioactive carcinogens are inhaled
asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere ...
, certain dioxins, and
tobacco Tobacco is the common name of several plants in the genus ''Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the chie ...
smoke. Although the public generally associates carcinogenicity with synthetic chemicals, it is equally likely to arise from both natural and synthetic substances. Carcinogens are not necessarily immediately
toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...
; thus, their effect can be insidious. Carcinogens, as mentioned, are agents in the environment capable of contributing to cancer growth. Carcinogens can be categorized into two different types: activation-dependent and activation-independent, and each nature impacts their level and type of influence when it comes to promoting cancer growth.  These can range from certain viruses, such as HPV, to an over-consumption of alcohol, or even excessive amounts of red and processed meats, therefore impacting a person's health in ways they may not immediately associate with cancer. Activation-independent carcinogens, such as ultraviolet rays or nitrosamines in tobacco products, possess characteristics enabling them to interact directly with DNA and other cellular components to cause harm.  These include not requiring metabolic action or molecular changes to act, which complements their ability to be electrically excited, permitting them to interact with oxygen and nitrogen atoms in negatively charged cellular environments.  This type of interaction leads to the alteration of DNA nucleotide bases, causing disarrangement of that genetic material.  This disarrangement is also responsible for the formation of DNA adducts, segments of DNA which bind to carcinogens, which furthers harm. Eventually, failure in DNA repair mechanisms will lead to a buildup of DNA damage and potentially the development of cancer. Cancer is any disease in which normal cells are damaged and do not undergo
programmed cell death Programmed cell death (PCD; sometimes referred to as cellular suicide) is the death of a cell (biology), cell as a result of events inside of a cell, such as apoptosis or autophagy. PCD is carried out in a biological process, which usually confers ...
as fast as they divide via mitosis. Carcinogens may increase the risk of cancer by altering cellular metabolism or damaging DNA directly in
cells 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 ...
, which interferes with
biological Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary in ...
processes, and induces the uncontrolled, malignant division, ultimately leading to the formation of tumors. Usually, severe DNA damage leads to programmed cell death, but if the programmed cell death pathway is damaged, then the cell cannot prevent itself from becoming a cancer cell. There are many natural carcinogens.
Aflatoxin Aflatoxins are various poisonous carcinogens and mutagens that are produced by certain molds, particularly ''Aspergillus'' species. The fungi grow in soil, decaying vegetation and various staple foodstuffs and commodities such as hay, sweetco ...
B1, which is produced by the fungus ''
Aspergillus flavus ''Aspergillus flavus'' is a saprotrophic and pathogenic fungus with a cosmopolitan distribution. It is best known for its colonization of cereal grains, legumes, and tree nuts. Postharvest rot typically develops during harvest, storage, and/or ...
'' growing on stored
grains A grain is a small, hard, dry fruit (caryopsis) – with or without an attached hull layer – harvested for human or animal consumption. A grain crop is a grain-producing plant. The two main types of commercial grain crops are cereals and legum ...
, nuts and peanut butter, is an example of a potent, naturally occurring microbial carcinogen. Certain viruses such as
hepatitis B Hepatitis B is an infectious disease caused by the ''Hepatitis B virus'' (HBV) that affects the liver; it is a type of viral hepatitis. It can cause both acute and chronic infection. Many people have no symptoms during an initial infection. For ...
and
human papilloma virus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the ''Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and re ...
have been found to cause cancer in humans. The first one shown to cause cancer in animals is Rous sarcoma virus, discovered in 1910 by
Peyton Rous Francis Peyton Rous () (October 5, 1879 – February 16, 1970) was an American pathologist at the Rockefeller University known for his works in oncoviruses, blood transfusion and physiology of digestion. A medical graduate from the Johns Hopk ...
. Other
infectious An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...
organisms which cause cancer in humans include some bacteria (e.g. '' Helicobacter pylori'' ) and helminths (e.g. '' Opisthorchis viverrini'' and ''
Clonorchis sinensis ''Clonorchis sinensis'', the Chinese liver fluke, is a liver fluke belonging to the class Trematoda, phylum Platyhelminthes. It infects fish-eating mammals, including humans. In humans, it infects the common bile duct and gall bladder, feeding on ...
''). Dioxins and dioxin-like compounds,
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
,
kepone Chlordecone, better known in the United States under the brand name Kepone, is an organochlorine compound and a colourless solid. It is an obsolete insecticide, now prohibited in the western world, but only after many thousands of tonnes had bee ...
, EDB, and
asbestos Asbestos () is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere ...
have all been classified as carcinogenic. As far back as the 1930s, industrial smoke and
tobacco Tobacco is the common name of several plants in the genus ''Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the chie ...
smoke were identified as sources of dozens of carcinogens, including benzo 'a''yrene, tobacco-specific nitrosamines such as nitrosonornicotine, and reactive
aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...
s such as formaldehyde, which is also a hazard in
embalming Embalming is the art and science of preserving human remains by treating them (in its modern form with chemicals) to forestall decomposition. This is usually done to make the deceased suitable for public or private viewing as part of the funeral ...
and making plastics.
Vinyl chloride Vinyl chloride is an organochloride with the formula H2C=CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC ...
, from which PVC is manufactured, is a carcinogen and thus a hazard in PVC production.
Co-carcinogen A co-carcinogen is a chemical that promotes the effects of a carcinogen in the production of cancer. Usually, the term is used to refer to chemicals that are not carcinogenic on their own, such that an equivalent amount of the chemical is insuf ...
s are chemicals that do not necessarily cause cancer on their own but promote the activity of other carcinogens in causing cancer. After the carcinogen enters the body, the body makes an attempt to eliminate it through a process called
biotransformation Biotransformation is the biochemical modification of one chemical compound or a mixture of chemical compounds. Biotransformations can be conducted with whole cells, their lysates, or purified enzymes. Increasingly, biotransformations are effected w ...
. The purpose of these reactions is to make the carcinogen more
water-soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solub ...
so that it can be removed from the body. However, in some cases, these reactions can also convert a less toxic carcinogen into a more toxic carcinogen. DNA is
nucleophilic In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
; therefore, soluble carbon electrophiles are carcinogenic, because DNA attacks them. For example, some
alkene In organic chemistry, an alkene is a hydrocarbon containing a carbon–carbon double bond. Alkene is often used as synonym of olefin, that is, any hydrocarbon containing one or more double bonds.H. Stephen Stoker (2015): General, Organic, a ...
s are
toxicated Toxication, toxification or toxicity exaltation is the conversion of a chemical compound into a more toxic form in living organisms or in substrates such as soil or water. The conversion can be caused by enzymatic metabolism in the organisms, as we ...
by human enzymes to produce an
electrophilic In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carri ...
epoxide. DNA attacks the epoxide, and is bound permanently to it. This is the mechanism behind the carcinogenicity of benzo 'a''yrene in tobacco smoke, other aromatics, aflatoxin and mustard gas.


Radiation

CERCLA Superfund is a United States federal environmental remediation program established by the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA). The program is administered by the Environmental Protection Agency ...
identifies all
radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...
s as carcinogens, although the nature of the emitted radiation (
alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whic ...
,
beta Beta (, ; uppercase , lowercase , or cursive ; grc, βῆτα, bē̂ta or ell, βήτα, víta) is the second letter of the Greek alphabet. In the system of Greek numerals, it has a value of 2. In Modern Greek, it represents the voiced labiod ...
, gamma, or neutron and the radioactive strength), its consequent capacity to cause
ionization Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
in tissues, and the magnitude of radiation exposure, determine the potential hazard. Carcinogenicity of radiation depends on the type of radiation, type of exposure, and penetration. For example,
alpha radiation Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an atomi ...
has low penetration and is not a hazard outside the body, but emitters are carcinogenic when inhaled or ingested. For example,
Thorotrast Thorotrast is a suspension containing particles of the radioactive compound thorium dioxide, ThO2; it was used as a radiocontrast agent in clinical radiography in the 1930s to 1950s. It is no longer used clinically. Thorium compounds produce ...
, a (incidentally radioactive) suspension previously used as a contrast medium in
x-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10  picometers to 10 nanometers, corresponding to frequencies in the range 30  ...
diagnostics, is a potent human carcinogen known because of its retention within various
organs In biology, an organ is a collection of tissues joined in a structural unit to serve a common function. In the hierarchy of life, an organ lies between tissue and an organ system. Tissues are formed from same type cells to act together in a ...
and persistent emission of alpha particles. Low-level ionizing radiation may induce irreparable DNA damage (leading to replicational and transcriptional errors needed for neoplasia or may trigger viral interactions) leading to pre-mature aging and cancer. Not all types of electromagnetic radiation are carcinogenic. Low-energy waves on the
electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from b ...
including
radio wave Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (shor ...
s,
microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...
s, infrared radiation and visible light are thought not to be, because they have insufficient energy to break chemical bonds. Evidence for carcinogenic effects of non-ionizing radiation is generally inconclusive, though there are some documented cases of radar technicians with prolonged high exposure experiencing significantly higher cancer incidence. Higher-energy radiation, including ultraviolet radiation (present in sunlight), x-rays, and gamma radiation, generally ''is'' carcinogenic, if received in sufficient doses. For most people, ultraviolet radiations from sunlight is the most common cause of skin cancer. In Australia, where people with pale skin are often exposed to strong sunlight, melanoma is the most common cancer diagnosed in people aged 15–44 years. Substances or foods irradiated with electrons or electromagnetic radiation (such as microwave, X-ray or gamma) are not carcinogenic. In contrast, non-electromagnetic neutron radiation produced inside nuclear reactors can produce secondary radiation through
nuclear transmutation Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed. A transmut ...
.


In prepared food

Chemicals used in processed and cured meat such as some brands of bacon, sausages and ham may produce carcinogens. For example, nitrites used as food preservatives in cured meat such as bacon have also been noted as being carcinogenic with demographic links, but not causation, to colon cancer. Cooking food at high temperatures, for example
grilling Grilling is a form of cooking that involves dry heat applied to the surface of food, commonly from above, below or from the side. Grilling usually involves a significant amount of direct, radiant heat, and tends to be used for cooking meat a ...
or
barbecuing Barbecue or barbeque (informally BBQ in the UK, US, and Canada, barbie in Australia and braai in South Africa) is a term used with significant regional and national variations to describe various cooking methods that use live fire and smoke t ...
meats, may also lead to the formation of minute quantities of many potent carcinogens that are comparable to those found in cigarette smoke (i.e., benzo 'a''yrene).
Charring Charring is a chemical process of incomplete combustion of certain solids when subjected to high heat. Heat distillation removes water vapour and volatile organic compounds (syngas) from the matrix. The residual black carbon material is char, as di ...
of food looks like
coking Coking is the heating of coal in the absence of oxygen to a temperature above 600 °C to drive off the volatile components of the raw coal, leaving a hard, strong, porous material of high carbon content called coke. Coke consists almost en ...
and tobacco pyrolysis, and produces carcinogens. There are several carcinogenic pyrolysis products, such as polynuclear aromatic hydrocarbons, which are converted by human enzymes into epoxides, which attach permanently to DNA. Pre-cooking meats in a microwave oven for 2–3 minutes before grilling shortens the time on the hot pan, and removes heterocyclic amine (HCA) precursors, which can help minimize the formation of these carcinogens. Baking, grilling or broiling food, especially starchy foods, until a toasted crust is formed generates significant concentrations of
acrylamide Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary ...
. 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 Cancer Research UK (CRUK) is the world's largest independent cancer research organization. It is registered as a charity in the United Kingdom and Isle of Man, and was formed on 4 February 2002 by the merger of The Cancer Research Campaign and t ...
categorizes the idea that burnt food causes cancer as a "myth".


In cigarettes

There is a strong association of smoking with lung cancer; the risk of developing lung cancer increases significantly in smokers. A large number of known carcinogens are found in cigarette smoke. Potent carcinogens found in cigarette smoke include
polycyclic aromatic hydrocarbon A polycyclic aromatic hydrocarbon (PAH) is a class of organic compounds that is composed of multiple aromatic rings. The simplest representative is naphthalene, having two aromatic rings and the three-ring compounds anthracene and phenanthrene. ...
s (PAH, such as benzo(a)pyrene),
benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
, and nitrosamine.


Mechanisms of carcinogenicity

Carcinogens can be classified as genotoxic or nongenotoxic.
Genotoxin 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 ...
s cause irreversible genetic damage or mutations by binding to DNA. Genotoxins include chemical agents like
N-nitroso-N-methylurea ''N''-Nitroso-''N''-methylurea (NMU) is a highly reliable carcinogen, mutagen, and teratogen. NMU is an alkylating agent, and exhibits its toxicity by transferring its methyl group to nucleobases in nucleic acids, which can lead to AT:GC tran ...
(NMU) or non-chemical agents such as ultraviolet light and ionizing radiation. Certain viruses can also act as carcinogens by interacting with DNA. Nongenotoxins do not directly affect DNA but act in other ways to promote growth. These include hormones and some organic compounds.


Classification


International Agency for Research on Cancer

The
International Agency for Research on Cancer The International Agency for Research on Cancer (IARC; french: Centre International de Recherche sur le Cancer, CIRC) is an intergovernmental agency forming part of the World Health Organization of the United Nations. Its role is to conduct and ...
(IARC) is an intergovernmental agency established in 1965, which forms part of the World Health Organization of the
United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizi ...
. It is based in
Lyon Lyon,, ; Occitan: ''Lion'', hist. ''Lionés'' also spelled in English as Lyons, is the third-largest city and second-largest metropolitan area of France. It is located at the confluence of the rivers Rhône and Saône, to the northwest of th ...
, France. Since 1971 it has published a series of ''Monographs on the Evaluation of Carcinogenic Risks to Humans'' that have been highly influential in the classification of possible carcinogens. *
Group 1 Group 1 may refer to: * Alkali metal, a chemical element classification for Alkali metal * Group 1 (racing) The Group 1 racing class referred to FIA regulations for cars in touring car racing and rallying. Throughout its existence the group reta ...
: the agent (mixture) is definitely carcinogenic to humans. The exposure circumstance entails exposures that are carcinogenic to humans. (Strongest tier for evidence of carcinogenity) * Group 2A: the agent (mixture) is probably (''product more likely to be'') carcinogenic to humans. The exposure circumstance entails exposures that are probably carcinogenic to humans. (There is a bunch of data liking it to carcinogenicity, some may not link it to carcinogenicity) * Group 2B: the agent (mixture) is possibly (''chance of product being'') carcinogenic to humans. The exposure circumstance entails exposures that are possibly carcinogenic to humans. (There is ''some'' data liking it to carcinogenicity) *
Group 3 Group 3 may refer to: *Group 3 element, chemical element classification *Group 3 (racing), FIA classification for auto racing * Group 3, the third tier of races in worldwide Thoroughbred horse racing * Group 3 image format, Group 3 & Group 4 are ...
: the agent (mixture or exposure circumstance) is not classifiable as to its carcinogenicity to humans. (A lack of data can make it fall into this category). Those could still be carginogenic or not. This category might be seen as the "default (or initial) category" *
Group 4 Group 4 may refer to: *Group 4 element, chemical element classification * Group 4 (racing), classification for cars in auto racing and rallying * G4S, formerly Group 4 Securicor, a prominent British security company *IB Group 4 subjects, subject gr ...
: the agent (mixture) is probably not carcinogenic to humans. (There is data mostly indicating ailing to findthat the mixture is carcinogenic).


Globally Harmonized System

The Globally Harmonized System of Classification and Labelling of Chemicals (GHS) is a
United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizi ...
initiative to attempt to harmonize the different systems of assessing chemical risk which currently exist (as of March 2009) around the world. It classifies carcinogens into two categories, of which the first may be divided again into subcategories if so desired by the competent regulatory authority: * Category 1: known or presumed to have carcinogenic potential for humans ** Category 1A: the assessment is based primarily on human evidence ** Category 1B: the assessment is based primarily on animal evidence * Category 2: suspected human carcinogens


U.S. National Toxicology Program

The National Toxicology Program of the
U.S. Department of Health and Human Services The United States Department of Health and Human Services (HHS) is a cabinet-level executive branch department of the U.S. federal government created to protect the health of all Americans and providing essential human services. Its motto is " ...
is mandated to produce a biennial ''Report on Carcinogens''. As of June 2011, the latest edition was the 12th report (2011).''Report on Carcinogens, Eleventh Edition''
; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program (2011).
It classifies carcinogens into two groups: * Known to be a human carcinogen * Reasonably anticipated being a human carcinogen


American Conference of Governmental Industrial Hygienists

The
American Conference of Governmental Industrial Hygienists The American Conference of Governmental Industrial Hygienists (ACGIH) is a professional association of industrial hygienists and practitioners of related professions, with headquarters in Cincinnati, Ohio. One of its goals is to advance worker p ...
(ACGIH) is a private organization best known for its publication of threshold limit values (TLVs) for occupational exposure and monographs on workplace chemical hazards. It assesses carcinogenicity as part of a wider assessment of the occupational hazards of chemicals. * Group A1: Confirmed human carcinogen * Group A2: Suspected human carcinogen * Group A3: Confirmed animal carcinogen with unknown relevance to humans * Group A4: Not classifiable as a human carcinogen * Group A5: Not suspected as a human carcinogen


European Union

The European Union classification of carcinogens is contained in the Regulation (EC) No 1272/2008. It consists of three categories: * Category 1A: Carcinogenic * Category 1B: May cause cancer * Category 2: Suspected of causing cancer The former European Union classification of carcinogens was contained in the Dangerous Substances Directive and the
Dangerous Preparations Directive The Dangerous Preparations Directive is a European Union directive in the field of occupational safety and health and consumer protection. It complements the Dangerous Substances Directive (67/548/EEC) and replaces a previous Dangerous Preparati ...
. It also consisted of three categories: * Category 1: Substances known to be carcinogenic to humans. * Category 2: Substances which should be regarded as if they are carcinogenic to humans. * Category 3: Substances which cause concern for humans, owing to possible carcinogenic effects but in respect of which the available information is not adequate for making a satisfactory assessment. This assessment scheme is being phased out in favor of the GHS scheme (see above), to which it is very close in category definitions.


Safe Work Australia

Under a previous name, the NOHSC, in 1999
Safe Work Australia Safe Work Australia is an Australian Government statutory agency established in 2009 under the Safe Work Australia Act 2008. Their primary responsibility is to improve work health and safety and workers’ compensation arrangements across Austra ...
published the Approved Criteria for Classifying Hazardous Substances OHSC:1008(1999)Safe Work Australia
, NOHSC. (1999). Approved criteria for classifying hazardous substances OHSC:1008(1999)§ 4.76. Accessed 21/05/2011
Section 4.76 of this document outlines the criteria for classifying carcinogens as approved by the Australian government. This classification consists of three categories: * Category 1: Substances known to be carcinogenic to humans. * Category 2: Substances that should be regarded as if they were carcinogenic to humans. * Category 3: Substances that have possible carcinogenic effects in humans but about which there is insufficient information to make an assessment.


Common carcinogens


Occupational carcinogens

Occupational carcinogens are agents that pose a risk of cancer in several specific work-locations: Disclaimer: ''The following list is far from being exhaustive.''


Others

* Gasoline (contains aromatics) * Lead and its compounds *
Alkylating antineoplastic agent An alkylating antineoplastic agent is an alkylating agent used in cancer treatment that attaches an alkyl group (CnH2n+1) to DNA. The alkyl group is attached to the guanine base of DNA, at the number 7 nitrogen atom of the purine ring. Since ...
s (e.g. mechlorethamine) *
Styrene Styrene () is an organic compound with the chemical formula C6H5CH=CH2. This derivative of benzene is a colorless oily liquid, although aged samples can appear yellowish. The compound evaporates easily and has a sweet smell, although high concen ...
*Other
alkylating agent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...
s (e.g. dimethyl sulfate) * Ultraviolet radiation from the sun and UV lamps *
Alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...
(causing head and neck cancers) * Other ionizing radiation (X-rays, gamma rays, etc.) * Low refining or unrefined
mineral oil Mineral oil is any of various colorless, odorless, light mixtures of higher alkanes from a mineral source, particularly a distillate of petroleum, as distinct from usually edible vegetable oils. The name 'mineral oil' by itself is imprecise, ...
s * Etc


Major carcinogens implicated in the four most common cancers worldwide

In this section, the carcinogens implicated as the main causative agents of the four most common cancers worldwide are briefly described. These four cancers are lung, breast, colon, and stomach cancers. Together they account for about 41% of worldwide cancer incidence and 42% of cancer deaths (for more detailed information on the carcinogens implicated in these and other cancers, see references).


Lung cancer

Lung cancer (pulmonary carcinoma) is the most common cancer in the world, both in terms of cases (1.6 million cases; 12.7% of total cancer cases) and deaths (1.4 million deaths; 18.2% of total cancer deaths). Lung cancer is largely caused by tobacco smoke. Risk estimates for lung cancer in the United States indicate that tobacco smoke is responsible for 90% of lung cancers. Other factors are implicated in lung cancer, and these factors can interact synergistically with smoking so that total attributable risk adds up to more than 100%. These factors include occupational exposure to carcinogens (about 9-15%), radon (10%) and outdoor air pollution (1-2%). Tobacco smoke is a complex mixture of more than 5,300 identified chemicals. The most important carcinogens in tobacco smoke have been determined by a "Margin of Exposure" approach. Using this approach, the most important tumorigenic compounds in tobacco smoke were, in order of importance, acrolein, formaldehyde, acrylonitrile, 1,3-butadiene, cadmium, acetaldehyde, ethylene oxide, and isoprene. Most of these compounds cause DNA damage by forming DNA adducts or by inducing other alterations in DNA. DNA damages are subject to error-prone DNA repair or can cause replication errors. Such errors in repair or replication can result in mutations in tumor suppressor genes or oncogenes leading to cancer.


Breast cancer

Breast cancer Breast cancer is cancer that develops from breast tissue. Signs of breast cancer may include a lump in the breast, a change in breast shape, dimpling of the skin, milk rejection, fluid coming from the nipple, a newly inverted nipple, or a r ...
is the second most common cancer 1.4 million cases, 10.9%), but ranks 5th as cause of death (458,000, 6.1%) Increased risk of breast cancer is associated with persistently elevated blood levels of estrogen. Estrogen appears to contribute to breast carcinogenesis by three processes; (1) the metabolism of estrogen to genotoxic, mutagenic carcinogens, (2) the stimulation of tissue growth, and (3) the repression of phase II
detoxification Detoxification or detoxication (detox for short) is the physiological or medicinal removal of toxic substances from a living organism, including the human body, which is mainly carried out by the liver. Additionally, it can refer to the period of ...
enzymes that metabolize ROS leading to increased oxidative DNA damage. The major estrogen in humans, estradiol, can be metabolized to quinone derivatives that form
adducts An adduct (from the Latin ''adductus'', "drawn toward" alternatively, a contraction of "addition product") is a product of a direct addition of two or more distinct molecules, resulting in a single reaction product containing all atoms of all co ...
with DNA. These derivatives can cause dupurination, the removal of bases from the phosphodiester backbone of DNA, followed by inaccurate repair or replication of the apurinic site leading to mutation and eventually cancer. This genotoxic mechanism may interact in synergy with estrogen receptor-mediated, persistent cell proliferation to ultimately cause breast cancer. Genetic background, dietary practices and environmental factors also likely contribute to the incidence of DNA damage and breast cancer risk.


Colon cancer

Colorectal cancer Colorectal cancer (CRC), also known as bowel cancer, colon cancer, or rectal cancer, is the development of cancer from the colon or rectum (parts of the large intestine). Signs and symptoms may include blood in the stool, a change in bowel m ...
is the third most common cancer .2 million cases (9.4%), 608,000 deaths (8.0%) Tobacco smoke may be responsible for up to 20% of colorectal cancers in the United States. In addition, substantial evidence implicates
bile acid Bile acids are steroid acids found predominantly in the bile of mammals and other vertebrates. Diverse bile acids are synthesized in the liver. Bile acids are conjugated with taurine or glycine residues to give anions called bile salts. Primary ...
s as an important factor in colon cancer. Twelve studies (summarized in Bernstein et al.) indicate that the bile acids deoxycholic acid (DCA) or lithocholic acid (LCA) induce production of DNA-damaging reactive oxygen species or reactive nitrogen species in human or animal colon cells. Furthermore, 14 studies showed that DCA and LCA induce DNA damage in colon cells. Also 27 studies reported that bile acids cause programmed cell death (
apoptosis Apoptosis (from grc, ἀπόπτωσις, apóptōsis, 'falling off') is a form of programmed cell death that occurs in multicellular organisms. Biochemical events lead to characteristic cell changes (morphology) and death. These changes includ ...
). Increased apoptosis can result in selective survival of cells that are resistant to induction of apoptosis. Colon cells with reduced ability to undergo apoptosis in response to DNA damage would tend to accumulate mutations, and such cells may give rise to colon cancer. Epidemiologic studies have found that fecal bile acid concentrations are increased in populations with a high incidence of colon cancer. Dietary increases in total fat or saturated fat result in elevated DCA and LCA in feces and elevated exposure of the colon epithelium to these bile acids. When the bile acid DCA was added to the standard diet of wild-type mice invasive colon cancer was induced in 56% of the mice after 8 to 10 months. Overall, the available evidence indicates that DCA and LCA are centrally important DNA-damaging carcinogens in colon cancer.


Stomach cancer

Stomach cancer is the fourth most common cancer 90,000 cases (7.8%), 738,000 deaths (9.7%) '' Helicobacter pylori'' infection is the main causative factor in stomach cancer. Chronic gastritis (inflammation) caused by ''H. pylori'' is often long-standing if not treated. Infection of gastric epithelial cells with ''H. pylori'' results in increased production of reactive oxygen species (ROS). ROS cause oxidative DNA damage including the major base alteration 8-hydroxydeoxyguanosine (8-OHdG). 8-OHdG resulting from ROS is increased in chronic gastritis. The altered DNA base can cause errors during DNA replication that have mutagenic and carcinogenic potential. Thus ''H. pylori''-induced ROS appear to be the major carcinogens in stomach cancer because they cause oxidative DNA damage leading to carcinogenic mutations. Diet is thought to be a contributing factor in stomach cancer - in Japan where very salty pickled foods are popular, the incidence of stomach cancer is high. Preserved meat such as bacon, sausages, and ham increases the risk while a diet high in fresh fruit and vegetables may reduce the risk. The risk also increases with age.


See also


References


External links


U.S. National Toxicology Program's Report on Carcinogens


* ttp://www.scorecard.org/health-effects/chemicals.tcl?short_hazard_name=cancer&all_p=t Recognized Carcinogens
American Cancer Society

Database of Rodent Carcinogens


{{Authority control Carcinogenesis Radiation health effects