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The main causes of cancer (including hazardous circumstances)


Glossary over The main causes of cancer (including hazardous circumstances)

Adverse health effect

A change in body function or cell structure that might lead to disease or health problems. (Source: ATSDR Glossary of Terms  )

Aerodynamic diameter

Airborne particles have irregular shapes, and their aerodynamic behaviour is expressed in terms of the diameter of an idealised spherical particle known as aerodynamic diameter.

Particles are sampled and described on the basis of their aerodynamic diameter, which is usually simply referred to as particle size.

Particles having the same aerodynamic diameter may have different dimensions and shapes. (Source: based on the GreenFacts Digest on Air Pollution)



Aflatoxins are potent toxic, carcinogenic, mutagenic, immunosuppressive substances that can be found on poorly stored grains and nuts.

They are produced as secondary metabolites by certain types of molds (Aspergillus flavus and Aspergillus parasiticus).

Food contaminated with aflatoxins can affect both humans and animals and lead to liver cancer. (Source: GreenFacts)


The term alcohol refers to a family of chemicals that occur widely in nature and are mass-produced for use in antifreezes, fuels and some manufacturing processes.

Alcohol is commonly used to refer to alcohol-containing drinks such as wine, beer and spirits. In this case the alcohol, ethanol, has been produced by a process called fermentation. Consumption of excessive amounts of alcohol can lead to drunkenness and may be harmful to health. (Source: GreenFacts)


Originating from the activity of humans. (Source: GreenFacts )


Antiviral drugs are used for treating viral infections. They do not kill the viruses but impede their development by suppressing their ability to multiply and reproduce. (Source: GreenFacts)



The smallest particle of an element that still conserves the chemical properties of that element. Atoms are composed of electrons, protons, and neutrons. (Source: GreenFacts)


Bacteria are a major group of micro-organisms that live in soil, water, plants, organic matter, or the bodies of animals or people. They are microscopic and mostly unicellular, with a relatively simple cell structure.

Some bacteria cause diseases such as tetanus, typhoid fever, pneumonia, syphilis, cholera, and tuberculosis.

Bacteria play a role in the decomposition of organic matter and other chemical processes. (Source: GreenFacts)



Bioaccumulation is used to describe the increase in concentration of a substance in an organism over time.

Bioaccumulative substances tend to be fat soluble and not to be broken down by the organism. (Source: GreenFacts )



According to the Biocides Directive (98/8/EC), biocidal products are those that are intended to destroy, render harmless, prevent the action of, or otherwise exert a controlling effect on any harmful organism by chemical or biological means. Examples include disinfectants, preservatives, antiseptics, pesticides, herbicides, fungicides and insecticides.

Biocidal products mentioned in the Biocides Directive are listed in the following table: (Source: GreenFacts, based on the Biocides Directive (98/8/EC)  )



The total quantity or mass of organic material produced by living organisms in a particular area, at a given time. (Source: GreenFacts)



The dense, living tissue that makes up the skeleton of humans and vertebrate animals.

Mature bones are made up of three types of tissue: compact tissue (the hard outer portion of most bones); cancellous tissue (spongy tissue inside the bones that contains bone marrow, which makes blood cells); and subchondral tissue (smooth bone tissue of the joints).

Cancellous tissue, also known as cancellous bone, spongy bone or trabecular bone, is characterized by its spongy, porous, honeycomb-like structure and is typically found at the ends of long bones. Compact tissue is also known as hard bone, compact bone or compact cortical bone. (Source: GreenFacts)



Any one of a group of diseases that occur when cells in the body become abnormal and have the potential to spread and establish growth in nearby tissues and other parts of the body (malignancy). (Source: GreenFacts )


Cancer risk

A theoretical risk for getting cancer if exposed to a substance every day for 70 years (a lifetime exposure). The true risk might be lower. (Source: ATSDR Glossary of Terms  )



A substance, factor or situation that causes or induces cancer. (Source: GreenFacts )


A carcinoma is a cancerous tumour that starts in tissues covering or lining various organs of the body or in glands, such as skin, uterus, prostate, breast, or stomach. Carcinomas tend to infiltrate into nearby tissues. They may also spread to distant organs such as lung, bone, liver, or the brain. Carcinomas are the most common type of cancer. (Source: GreenFacts)


Chlorine (Cl2) is produced in large amounts and widely used both industrially and domestically as a disinfectant and bleach. In particular, it is widely used in the disinfection of swimming pools and is the most commonly used disinfectant and oxidant for drinking-water treatment. In water, chlorine reacts to form hypochlorous acid and hypochlorites. (Source: WHO  Guidelines for drinking water quality )


One of the threadlike "packages" of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs of chromosomes, 46 in all: 44 autosomes and two sex chromosomes. Each parent contributes one chromosome to each pair, so children get half of their chromosomes from their mothers and half from their fathers. (Source: NHGRI Talking Glossary of Genetic Terms  )


Cohort study

A type of epidemiological study which observes a large number of individuals in a population over a period of time.

It compares individuals who are exposed for instance to a certain chemical to others without the exposure or with a different level of exposure. These two groups are called cohorts and are followed over time to determine the differences in the health outcomes between the exposure subjects. (Source: GreenFacts)


Relating to or affecting the colon and the rectum. (Source: GreenFacts)



A material made up of two or more elements combined in a fixed ratio. (Source: CoRIS glossary  )



A substance that is either present in an environment where it does not belong or is present at levels that might cause harmful effects to humans or the environment. (Source: GreenFacts)


Diabetes is a disease that develops when the body is unable to produce or respond to insulin hormone in the normal way. (Source: GreenFacts)


Digestive tract

The digestive tract is the system of organs which takes in food, digests it to extract energy and nutrients and expels remaining waste. It includes the mouth, salivary glands, esophagus, stomach, pancreas, liver, gallbladder, small intestine, large intestine, and rectum.

After food is chewed and swallowed, the digestive juices released by the pancreas and stomach break it down into substances that are readily absorbed through the small intestine. Material that is not taken up by the body collects in the large intestine, forming faecal matter that is then excreted through the anus. (Source: GreenFacts)



"Dioxins" refers to a group of chlorinated organic chemicals with similar chemical structures.

In all GreenFacts publications the term "dioxins" is used to cover both polychlorinated dibenzo-dioxins (PCDDs) and polychlorinated dibenzo-furans (PCDFs). Other sources may refer to these compounds as "dioxins and furans".

Some dioxins have harmful properties, depending on the number and position of chlorine atoms. One of the most toxic dioxin is known as TCDD (2,3,7,8 tetrachlorodibenzo-p-dioxin). Some PCBs which have similar properties are considered "dioxin-like". (Source: GreenFacts)


Electromagnetic fields (EMF)

Electromagnetic fields (EMF) are a combination of invisible electric and magnetic fields of force. They occur both naturally and due to human activity. (Source: GreenFacts)


Electromagnetic spectrum

The electromagnetic spectrum is the entire range of wavelengths of all known electromagnetic radiations. It includes:

Gamma rays have the smallest wavelengths and highest frequencies known. They are high energy waves capable of travelling long distances through air and are the most penetrating waves.

X-rays have longer wavelengths than gamma rays but smaller wavelengths and therefore higher energy than ultraviolet radiation. They have been used in various applications in science and industry and are primarily used in medicine for instance in radiography. They are a form of ionizing radiation and as such can be dangerous. X-rays are emitted by electrons outside the nucleus, while gamma rays are emitted by the nucleus.

Ultraviolet (UV) radiation is defined as the portion of the electromagnetic spectrum between X-rays and visible light. More...

Visible light – also known as the visible spectrum – is the portion of the electromagnetic spectrum that human eyes can detect. It covers all colours from blue at 400 nm to red at 700 nm, with blue light having more energy than red light.

Infrared (IR) radiation – also referred to as thermal radiation – is the portion of the electromagnetic spectrum lying between visible light and microwaves. The most important natural source of infrared radiation is the sun.

Radio waves have long wavelengths, ranging from a few centimetres to many thousands of kilometres in length. They are used among other things for television, cell phone and radio communications. (Source: GreenFacts)


Elemental Arsenic

The element with the symbol "As" and the atomic number 33. Its molecular weight is 74.92160 g. It can be classified as semi metallic and its colour is observed to be metallic grey. (Source: GreenFacts)



Found only in a certain strictly limited geographical region, i.e. restricted to a specified region or locality. Can apply for instance to a disease or to an animal or plant species. (Source: GreenFacts)

Endometrial tissue

The layer of tissue that lines the uterus. (Source: NCI Dictionary of Cancer Terms  )

Epidemiological studies

Studies on human populations, which attempt to link human health effects (e.g. cancer) to a cause (e.g. exposure to a specific chemical). (Source: GreenFacts)



The muscular tube through which food passes from the pharynx to the stomach. (Source: GreenFacts)


Primary female sex hormone produced mainly by the ovaries. Estrogens are also produced in smaller amounts in the testes of men.

In women, estrogens are primarily involved with the development of female sexual characteristics and the maintenance of the reproductive system and menstrual cycle.

Estrogens are also thought to be important in the development of nerve cells and in the maintenance of a healthy heart.



Contact of the cells of an organism with a substance, micro-organism or radiation. In the case of humans, this may involve contact with a substance or agent by swallowing, breathing, or through the skin or eyes. Exposure may be short-term [acute exposure], of intermediate duration, or long-term [chronic exposure].

Exposure can be divided into external and internal.

External exposure refers to the whole dose to which an organism is exposed.

Internal exposure refers only to that fraction of the initial chemical dose that is absorbed and distributed throughout the body via systemic circulation. (Source: GreenFacts)


Exposure assessment(s)

Quantitative or qualitative evaluation of the contact of a chemical [or a physical factor] with the outer boundary of the human body, which includes consideration of the intensity, frequency and duration of contact, the route of exposure (e.g. dermal, oral or respiratory), rates (chemical intake or uptake rates), the resulting amount that actually crosses the boundary (dose), and the amount absorbed (internal dose) (WHO 1999). (Source: EMCOM Glossary  )


The ability of people or animals to produce healthy offspring in abundance.

Unlike fecundity, which measures a potential ability, fertility measures the actual number of offspring of an individual, a couple, a group or a population. It is evaluated by the time to achieve pregnancy.

Please note that "fertility" corresponds to "fécondité" in French and "fecundidad" in Spanish whereas the French word "fertilité" and the Spanish word "fertilidad" mean "fecundity". (Source: GreenFacts)

Food web

The interconnected food chains (feeding relationships) in an ecosystem. Plants, herbivores, and carnivores all form parts of the food web. (Source: GreenFacts)



A colorless, pungent, and irritating volatile organic compound (VOC), with formula H2CO, used in manufacturing and chemical industries, and as a preservative by anatomists, embalmers, and pathologists. Potential sources in the home include pressed wood products such as particleboard or fiberboard, smoking, glues and adhesives, etc.

Formaldehyde is a known human carcinogen. (Source: GreenFacts)

Gall bladder

An organ that stores bile after it has been produced in the liver and before it is needed in the intestine where it aids the digestion of fats. (Source: GreenFacts)


Gene expression

The process by which a gene is "turned on" to produce the specific biological molecule encoded by that gene (usually protein or RNA). (Source: GreenFacts )


The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein. (Source: NHGRI Talking Glossary of Genetic Terms  )

Heavy metals

Metallic elements with high atomic weights, e.g. mercury, chromium, cadmium, arsenic, and lead.

They can damage living things at low concentrations and tend to accumulate in the food chain. (Source: US EPA Drinking Water Glossary  )


Inflammation of the liver caused by viruses (viral hepatitis) or by chronic exposure to medicines or toxins such as alcohol.

Symptoms include jaundice (yellowing of the skin caused by the buildup of bile pigments in the body), fever, appetite loss and gastrointestinal upset. (Source: GreenFacts)



Any chemical substance designed to kill or inhibit the growth of certain plants that are considered undesirable. (Source: GreenFacts)


Chemical messengers that help our body do different tasks. Hormones are produced by the endocrine glands and then sent all over the body to stimulate certain activities. For example, insulin is a well-known hormone that helps our body digest food. Hormones regulate our growth, digestion, reproduction and sexual function. (Source: EMCOM Endocrine disruptors glossary  )


It is the growth of a parasite within the human body that causes illness. It can be a virus, a bacteria, a fungus or a protozoa. (Source: GreenFacts )


Inflammation is the reaction of living tissues to infection, irritation or other injury. (Source: GreenFacts)



The act of swallowing something through eating, drinking, or mouthing objects. A hazardous substance can enter the body this way. (Source: ATSDR Glossary of Terms  )


The act of breathing.

A hazardous substance can enter the body by inhaling an airborne substance or contaminant in the form of gas, fumes mists, vapors, dusts, or aerosols. Once inhaled, contaminants can be deposited in the lungs and/or transported into the blood. (Source: GreenFacts)

Inorganic arsenic compound(s)

Sometimes referred to in short as inorganic arsenic, inorganic arsenic compound contain arsenic (As) and at least one other element, but no carbon (C). Inorganic arsenic exists in four main chemical forms known as valency or oxidation states. Valency is a measure of the ability of a compound to combine with other elements, such as hydrogen.

The dominant forms are:

  • Arsenite, with a valency of 3, also referred to as trivalent arsenic (As (III), As+3), and
  • Arsenate, with a valency of 5, also referred to as pentavalent arsenic (As (V), As+5



A substance that kills insects. (Source: FAO Glossary of biotechnology & genetic engineering  )


A hormone made by [certain] cells of the pancreas. Insulin controls the amount of sugar in the blood by moving it into the cells, where it can be used by the body for energy. (Source: St Jude's Children's Hospital: Medical Terminology & Drug Database  )


International Agency for Research on Cancer

"The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO).

IARC's mission is to coordinate and conduct research on the causes of human cancer, the mechanisms of carcinogenesis, and to develop scientific strategies for cancer control. The Agency is involved in both epidemiological and laboratory research and disseminates scientific information through publications, meetings, courses, and fellowships."

It has collaborated to and published many highly recognized scientific publications.

Most publications are availaible from the webpage IARC Monographs Programme on the Evaluation of Carcinogenic Risks to humans , "The IARC Monographs series publishes authoritative independent assessments by international experts of the carcinogenic risks posed to humans by a variety of agents, mixtures and exposures."

IARC distinguishes between four groups of compounds or physical factors based on the existing scientific evidence for carcinogenicity: Standard IARC classification (Source: IARC website  )


In the context of genetically modified crops, invasiveness refers to the ability of a plant to spread beyond its introduction site and become established in new locations, where it may have a deleterious effect on organisms already existing there. (Source: GreenFacts, based on FAO Glossary of biotechnology & genetic engineering  )


The larynx (voice box) is the upper end of the trachea (windpipe) that contains the vocal cords. It is the organ of voice production.

The larynx is the cornerstone of the aerodigestive system. It is related to three functions:

  • deglutition
  • respiration
  • phonation
(Source: GreenFacts)


An area of abnormal tissue. A lesion may be benign (non-cancercous) or malignant (cancerous). (Source: NCI dictionary  )


Leukaemia is a cancer that starts in blood-forming tissue such as the bone marrow, which makes blood cells (red blood cells that carry oxygen around the body, white blood cells that fight disease and infection, platelets that help to stop bleeding when it starts).

In people with leukaemia, the bone marrow produces large numbers of abnormal white blood cells and not enough normal red blood cells.

Leukaemia cases represent less than 4% of all cancer cases in adults but are the most common form of cancer in children.

There are different types of leukaemia (e.g. acute, chornic, myeloid and lymphoid leukaemia). (Source: GreenFacts )


An essential structural component of living cells, lipids are a class of oily organic compounds which are insoluble in water but soluble in fats and oils. The lipid class of molecules mainly consists of fats, oils and waxes. (Source: GreenFacts)



The liver is a big reddish-brow organ lying beneath the diaphragm on the right side. The liver is made up for a great part of liver cells which absorb nutrients and detoxify and remove harmful substances from the blood such as drugs and alcohol. The liver has many other vital functions and there is currently no way to compensate for the absence of liver.

Other liver functions include:

  • controlling levels of fats, amino acids and glucose in the blood
  • fighting infections in the body, particularly infections arising in the bowel.
  • manufacturing bile, a kind of digestive juice which aids in the digestion of fats
  • storing iron, certain vitamins and other essential chemicals
  • breaking down food and turning it into energy
  • manufacturing, breaking down and regulating numerous hormones
  • making enzymes and proteins which are responsible for most chemical reactions in the body, for example those involved in blood clotting and repair of damaged tissues.

Cancer that begins in cells of the immune system (the lymphatic system).

The most common type of lymphoma is called Hodgkin's lymphoma or Hodgkin's disease.

All other lymphomas are grouped together under the term non-Hodgkin's lymphoma. (Source: GreenFacts)


Cancerous. Progressive and uncontrolled growth. Malignant neoplasms or tumours can invade and destroy other tissues and spread to other parts of the body via the bloodstream or lymphatics (metastasis). (Source: GreenFacts )


A substance that is the product of biological changes to a chemical. (Source: US EPA Glossary  )



CH3OH. Methanol is the simplest alcohol and is toxic. At high concentrations, methanol can cause headaches, dizziness, nausea, vomiting, and death. Acute exposure may cause blindness. Chronic exposure to methanol can cause liver damage. (Source: GreenFacts )



Mathematical representation or simulation of an actual situation. (Source: GreenFacts)


A disease or the incidence of a disease within a population. (Source: GreenFacts)


Death. Usually the cause (a specific disease, a condition, or an injury) is stated. (Source: ATSDR Glossary of Terms   )


Any permanent change in the DNA of a cell.

Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment.

Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited.

Certain mutations may lead to cancer or other diseases. (Source: NCI dictionary   )

Nitrate & Nitrite

Nitrate [NO3-]and nitrite [NO2-] are naturally occurring ions that are part of the nitrogen cycle. Nitrate is used mainly in inorganic fertilizers, and sodium nitrite is used as a food preservative, especially in cured meats. The nitrate concentration in groundwater and surface water is normally low but can reach high levels as a result of agricultural [activity and] runoff, refuse dump runoff, or contamination with human or animal wastes. (Source: Safe Water for International Travelers Water Quality Standards; Nitrate )



The approximately 20 chemical elements known to be essential for the growth of living organisms, including nitrogen, sulfur, phosphorus, and carbon. (Source: Millennium Ecosystem Assessment Glossary   )



Obesity is defined as a Body Mass Index (BMI) of 30.0 or greater (Source: GreenFacts, based on WHO Obesity  )



A large, elongated gland located behind the lower portion of the stomach that secretes the hormones insulin and glucagon into the blood. These hormones are essential in regulating blood sugar levels.

The pancreas also secretes enzymes into the small intestine that help with digestion and neutralize acid from the stomach. (Source: GreenFacts)



An epidemic that is geographically widespread; occurring throughout a region or even throughout the world. (Source: CoRIS Glossary  )


Particulate matter

Sum of all microscopic solid and liquid particles, of human and natural origin, that remain suspended in a medium such as air for some time. These particles vary greatly in size, composition, and origin, and may be harmful.

Particulate matter may be in the form of fly ash, soot, dust, fog, fumes etc. (Source: GreenFacts)



Polychlorinated biphenyls (PCBs) are a family of 209 congeners of structurally similar organic chemicals, ranging from oily liquids to waxy solids. There are 12 PCBs that are dioxin-like and can similarly be toxic and non-toxic. One dioxin-like PCB is 3,4,4',5-Tetrachlorobiphenyl.

PCBs are synthetic and produced either as a singular congener, as a homogeneous group or as a mixture. They are non-flammable, stable, have a high boiling point and exhibit electrical insulating properties. As such, PCBs have been used as coolants and lubricants in transformers and other electrical equipment, as hydraulic fluids, and as plasticizers, pigments, dyes and carbonless copy paper ink. They are also generated and released into the environment as waste byproducts of chemical manufacturing and incineration. (Source: GreenFacts)


Persistent organic pollutants

Persistent organic pollutants (POPs) are chemical substances that persist in the environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment. This group of priority pollutants consists of pesticides (such as DDT), industrial chemicals (such as polychlorinated biphenyls, PCBs) and unintentional by-products of industrial processes (such as dioxins and furans).

Persistent Organic Pollutants are transported across international boundaries far from their sources, even to regions where they have never been used or produced. (Source: European Commission Environment DG POPs  )


A toxic chemical product that kills harmful organisms (e.g., insecticides, fungicide, weedicides, rodenticides, acaricides). (Source: FAO Glossary of biotechnology & genetic engineering  )



The pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus. In mammals, it is where the digestive tract and the respiratory tract cross, commonly called the "throat" (which term may also include the larynx). The human pharynx is bent at a sharper angle than other mammal pharynges, enabling us to produce a wider variety of sounds, but also putting us in danger of choking.

The human pharynx is divided into three sections: the nasopharynx, lying behind the nasal cavity; the oropharynx, behind the oral cavity [including soft palate, base of the tongue and tonsils]; and the laryngopharynx [also named hypopharynx], posterior to the larynx. (Source: GreenFacts )


Polycyclic aromatic hydrocarbons

A group of over 100 different organic compounds composed of several benzene rings. Some of them are persistent and carcinogenic.

PAHs are commonly formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat.

Generally, tobacco smoke is by far the most important source of exposure for humans. (Source: GreenFacts)


Primary & secondary particles

Primary particles are directly released into the atmosphere by wind, combustion processes, or human activities.

Secondary particles are those that form in the atmosphere from other gaseous pollutants, particularly sulfur dioxide, nitrogen oxides, ammonia, and volatile organic compounds. (Source: GreenFacts)

Primary & Secondary pollutant

A primary pollutant is an air pollutant emitted directly from a source.

A secondary pollutant is not directly emitted as such, but forms when other pollutants (primary pollutants) react in the atmosphere.

Examples of a secondary pollutant include ozone, which is formed when hydrocarbons (HC) and nitrogen oxides (NOx) combine in the presence of sunlight; NO2, which is formed as NO combines with oxygen in the air; and acid rain, which is formed when sulfur dioxide or nitrogen oxides react with water. (Source: GreenFacts)


A large molecule composed of one or more chains of amino acids in a specific order, formed according to genetic information.


Radiation dose

The radiation dose is the amount of energy from radiation that is actually absorbed by the body. This is not the same as measurements of the amount of radiation in the environment.

(Source: ATSDR Glossary   )


A radioactive gas that is released by the breakdown of uranium, a substance found in some soils and rocks. It can get inside buildings by diffusing through the soil and can also be released from concrete.

Breathing in too much radon can damage lung cells and lead to lung cancer. (Source: GreenFacts )

Risk assessment

A scientifically based process consisting of four steps:

  • hazard identification,
  • hazard characterization,
  • exposure assessment and
  • risk characterization
(Source:   Official Journal of the European Communities 2002 L 31 )


Skin cancer

A tumour that grows from skin cells and which can have different causes, including repeated severe sunburns or long-term exposure to the sun. (Source: GreenFacts, based on EcoHealth; Glossary   )


Solid cancer

Solid cancers are defined as abnormal cellular growths in "solid" organs such as the breast or prostate, as opposed to leukemia, a cancer affecting the blood, which is liquid. (Source: GreenFacts)

Standard IARC classification

Compounds or physical factors assessed by IARC (International Agency for Research on Cancer) are classified in four groups based on the existing scientific evidence for carcinogenicity.

Group 1: "Carcinogenic to humans" There is enough evidence to conclude that it can cause cancer in humans.
IARC definition and list of compounds

Group 2A: "Probably carcinogenic to humans" There is strong evidence that it can cause cancer in humans, but at present it is not conclusive.
IARC definition and list of compounds

Group 2B: "Possibly carcinogenic to humans" There is some evidence that it can cause cancer in humans but at present it is far from conclusive.
IARC definition and list of compounds

Group 3: "Unclassifiable as to carcinogenicity in humans" There is no evidence at present that it causes cancer in humans.
IARC definition and list of compounds

Group 4: "Probably not carcinogenic to humans" There is strong evidence that it does not cause cancer in humans.
IARC definition and compound listed

Standard IARC classification categorization descriptions

Group 1: "The agent (mixture) is carcinogenic to humans . The exposure circumstance entails exposures that are carcinogenic to humans."

"This category is used when there is sufficient evidence of carcinogenicity in humans. Exceptionally, an agent (mixture) may be placed in this category when evidence of carcinogenicity in humans is less than sufficient but there is sufficient evidence of carcinogenicity in experimental animals and strong evidence in exposed humans that the agent (mixture) acts through a relevant mechanism of carcinogenicity."

Examples include asbestos, benzene and ionizing radiation.
List of agents evaluated as group 1 to date. 

Group 2 (A and B): "This category includes agents, mixtures and exposure circumstances for which, at one extreme, the degree of evidence of carcinogenicity in humans is almost sufficient, as well as those for which, at the other extreme, there are no human data but for which there is evidence of carcinogenicity in experimental animals. Agents, mixtures and exposure circumstances are assigned to either group 2A (probably carcinogenic to humans) or group 2B (possibly carcinogenic to humans) on the basis of epidemiological and experimental evidence of carcinogenicity and other relevant data."

Group 2A: "The agent (mixture) is probably carcinogenic to humans . The exposure circumstance entails exposures that are probably carcinogenic to humans."

"This category is used when there is limited evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals. In some cases, an agent (mixture) may be classified in this category when there is inadequate evidence of carcinogenicity in humans and sufficient evidence of carcinogenicity in experimental animals and strong evidence that the carcinogenesis is mediated by a mechanism that also operates in humans. Exceptionally, an agent, mixture or exposure circumstance may be classified in this category solely on the basis of limited evidence of carcinogenicity in humans."

Examples include diesel engine exhaust, Formaldehyde and PCBs.
List of agents evaluated as group 2A to date. 

Group 2B: "The agent (mixture) is possibly carcinogenic to humans. "

"The exposure circumstance entails exposures that are possibly carcinogenic to humans.

This category is used for agents, mixtures and exposure circumstances for which there is limited evidence of carcinogenicity in humans and less than sufficient evidence of carcinogenicity in experimental animals. It may also be used when there is inadequate evidence of carcinogenicity in humans but there is sufficient evidence of carcinogenicity in experimental animals. In some instances, an agent, mixture or exposure circumstance for which there is inadequate evidence of carcinogenicity in humans but limited evidence of carcinogenicity in experimental animals together with supporting evidence from other relevant data may be placed in this group."

Examples include glass wool, styrene and gasoline exhaust.
List of agents evaluated as group 2B to date. 

Group 3: "The agent (mixture) is unclassifiable as to carcinogenicity in humans. "

"This category is used most commonly for agents, mixtures and exposure circumstances for which the evidence of carcinogenicity is inadequate in humans and inadequate or limited in experimental animals. Exceptionally, agents (mixtures) for which the evidence of carcinogenicity is inadequate in humans but sufficient in experimental animals may be placed in this category when there is strong evidence that the mechanism of carcinogenicity in experimental animals does not operate in humans.

Agents, mixtures and exposure circumstances that do not fall into any other group are also placed in this category."

Examples include anthracene, caffeine and fluorescent lighting.
List of agents evaluated as group 3 to date. 

Group 4: "The agent (mixture) is probably not carcinogenic to humans."

"This category is used for agents or mixtures for which there is evidence suggesting lack of carcinogenicity in humans and in experimental animals. In some instances, agents or mixtures for which there is inadequate evidence of carcinogenicity in humans but evidence suggesting lack of carcinogenicity in experimental animals, consistently and strongly supported by a broad range of other relevant data, may be classified in this group."

The only agent in that group is: Caprolactam (see Group 4 to date ) (Source: IUPAC Glossary of Terms Used in Toxicology Classification of carcinogenicity  )


A surfactant is a substance that reduces the surface tension of a liquid in which it is dissolved.

When dissolved in water a surfactant gives a product the ability to remove dirt from surfaces such as the human skin, textiles, and other solids. (Source: GreenFacts)

The International Renewable Energy Agency

The International Renewable Energy Agency (IRENA) is an intergovernmental organisation that supports countries in their transition to a sustainable energy future, and serves as the principal platform for international cooperation, a centre of excellence, and a repository of policy, technology, resource and financial knowledge on renewable energy. IRENA promotes the widespread adoption and sustainable use of all forms of renewable energy, including bioenergy, geothermal, hydropower, ocean, solar and wind energy in the pursuit of sustainable development, energy access, energy security and low-carbon economic growth and prosperity. (Source:  )


Measures taken to treat a physical or mental disease.

First-line therapy is the first type of therapy given for a condition or disease.

Second-line therapy is the treatment that is given when initial treatment (first-line therapy) doesn't work, or stops working. (Source: based on St Jude Hospital Medical Terminology & Drug Database )

Thyroid gland

The thyroid gland consists of two bodies like small walnuts; they are connected by an isthmus beside the larynx (voice box). The thyroid gland produces thyroid hormones T3 and T4 which regulate the metabolism of all cells in the body. Disorders of the thyroid gland are characterized by the inability to produce or release sufficient thyroid hormones (hypothyroidism) or the overactivity of the thyroid gland (hyperthyroidism). (Source: EMCOM Endocrine Disruptors Glossary  )



A group of cells joined to perform a set of functions. (Source: GreenFacts)


Able to poison or harm an organism. Toxic substances can cause adverse health effects. (Source: GreenFacts)


An abnormal mass of tissue resulting from uncontrolled and excessive cell division.

Tumours can be either benign (localised, without the invasion of other tissues) or malignant (showing progressive invasion of other tissues). (Source: GreenFacts)

Ultraviolet radiation

Electromagnetic radiation of shorter wavelength than visible light but of longer wavelenght than x-rays, i.e. ranging from approximately 400 nm to 100 nm.

The most common source of ultraviolet radiation is the sun, but it can also be produced artificially by UV lamps.

UV radiation is divided into three bands: UVA, UVB, and UVC. All three bands are classified as a probable human carcinogen.

UVA – Long-wavelength UVA covers the range 315–400 nm. Not significantly filtered by the atmosphere. Approximately 90% of UV radiation reaching the Earth’s surface. UVA is again divided into UVA-I (340 nm - 400 nm) and UVA-II (315 nm - 340 nm).

UVB – Medium-wavelength UVB covers the range 280–315 nm. Approximately 10% of UV radiation reaching the Earth’s surface.

UVC – Short-wavelength UVC covers the range 100–280 nm. All solar UVC radiation is absorbed by the ozone layer. (Source: GreenFacts based on WHO  Artificial tanning sunbeds: risks and guidance )



Method to improve a person’s immunity to a particular infectious disease. It involves the administration (oral intake or injection) of a vaccine, which is a weakened, dead or inactivated form of the pathogen responsible for the infection. This stimulates the immune system which produces antibodies (Source: GreenFacts)


A virus is a small organism which can infect other biological organisms.

Viruses can only reproduce by invading and taking over cells as they lack the cellular machinery for self reproduction.

They cause diseases in human beings, animals, plants and bacteria.

Examples of human diseases caused by viruses include the common cold, influenza, small pox, AIDS, and cold sores. (Source: GreenFacts)



Vitamins are a group of organic micronutrients that are required by the body for healthy growth, development and immune system functioning.

Certain vitamins are produced by the body but most vitamins are obtained from food or from manufactured dietary supplements. (Source: GreenFacts)


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