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The Ames test is a widely employed method that uses bacteria to test whether a given chemical can cause mutations in the DNA of the test organism. More formally, it is a biological assay to assess the mutagenic potential of chemical compounds. A positive test indicates that the chemical is mutagenic and therefore may act as a carcinogen, because cancer is often linked to mutation. The test serves as a quick and convenient assay to estimate the carcinogenic potential of a compound because standard carcinogen assays on mice and rats are time-consuming and expensive. However, false-positives and false-negatives are known.
A carcinogen also known as cancerogen 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 substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example gamma rays and alpha particles, which they emit. Common examples of non-radioactive carcinogens are inhaled asbestos, certain dioxins, and tobacco 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; thus, their effect can be insidious.
In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer in animals, such mutagens can therefore be carcinogens, although not all necessarily are. All mutagens have characteristic mutational signatures with some chemicals becoming mutagenic through cellular processes.
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 substructure of the organism, such as a cell (cytotoxicity) or an organ such as the liver (hepatotoxicity). By extension, the word may be metaphorically used to describe toxic effects on larger and more complex groups, such as the family unit or society at large. Sometimes the word is more or less synonymous with poisoning in everyday usage.
Erythritol is an organic compound, a sugar alcohol (or polyol), used as a food additive and sugar substitute. It is naturally occurring. It can be made from corn using enzymes and fermentation. Its formula is C
4H
10O
4, or HO(CH2)(CHOH)2(CH2)OH; specifically, one particular stereoisomer with that formula.
VSD may refer to:
The linear no-threshold model (LNT) is a dose-response model used in radiation protection to estimate stochastic health effects such as radiation-induced cancer, genetic mutations and teratogenic effects on the human body due to exposure to ionizing radiation. The model statistically extrapolates effects of radiation from very high doses into very low doses, where no biological effects may be observed. The LNT model lies at a foundation of a postulate that all exposure to ionizing radiation is harmful, regardless of how low the dose is, and that the effect is cumulative over lifetime.
Radiation hormesis is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation. The reserve repair mechanisms are hypothesized to be sufficiently effective when stimulated as to not only cancel the detrimental effects of ionizing radiation but also inhibit disease not related to radiation exposure. This hypothesis has captured the attention of scientists and public alike in recent years.
Estragole is a phenylpropene, a natural organic compound. Its chemical structure consists of a benzene ring substituted with a methoxy group and an allyl group. It is an isomer of anethole, differing with respect to the location of the double bond. It is a colorless liquid, although impure samples can appear yellow. It is a component of various trees and plants, including turpentine, anise, fennel, bay, tarragon, and basil. It is used in the preparation of fragrances.
The dose–response relationship, or exposure–response relationship, describes the magnitude of the response of an organism, as a function of exposure to a stimulus or stressor after a certain exposure time. Dose–response relationships can be described by dose–response curves. This is explained further in the following sections. A stimulus response function or stimulus response curve is defined more broadly as the response from any type of stimulus, not limited to chemicals.
Hexachlorobenzene, or perchlorobenzene, is an organochloride with the molecular formula C6Cl6. It is a fungicide formerly used as a seed treatment, especially on wheat to control the fungal disease bunt. It has been banned globally under the Stockholm Convention on Persistent Organic Pollutants.
Ethyl acrylate is an organic compound with the formula CH2CHCO2CH2CH3. It is the ethyl ester of acrylic acid. It is a colourless liquid with a characteristic acrid odor. It is mainly produced for paints, textiles, and non-woven fibers. It is also a reagent in the synthesis of various pharmaceutical intermediates.
4,4′-Methylenebis(2-chloroaniline) is a substance used as a curing agent in polyurethane production. MOCA is an aromatic amine which is structurally similar to benzidine, a known human bladder carcinogen. MOCA has been shown to cause hepatomas in mice and rats, lung and mammary carcinomas in rats and bladder cancer in dogs. It is a proven human carcinogen standing on the WHO List of IARC Group 1 carcinogens, with a current threshold limit value of 0.01 ppm in the industrial atmosphere. Animal studies have resulted in tumor growth in the liver, lung, and bladder.
Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environment. They are mostly by-products of burning or various industrial processes - or, in case of dioxin-like PCBs and PBBs, unwanted minor components of intentionally produced mixtures.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a polychlorinated dibenzo-p-dioxin (sometimes shortened, though inaccurately, to simply 'dioxin') with the chemical formula C12H4Cl4O2. Pure TCDD is a colorless solid with no distinguishable odor at room temperature. It is usually formed as an unwanted product in burning processes of organic materials or as a side product in organic synthesis.
Radon, a radioactive, colorless, odorless, tasteless noble gas, has been studied by a number of scientific and medical bodies for its effects on health. A naturally-occurring gas formed as a decay product of radium, radon is one of the densest substances that remains a gas under normal conditions, and is considered to be a health hazard due to its radioactivity. Its most stable isotope, radon-222, has a half-life of 3.8 days. Due to its high radioactivity, it has been less well studied by chemists, but a few compounds are known.
Cancer slope factors (CSF) are used to estimate the risk of cancer associated with exposure to a carcinogenic or potentially carcinogenic substance. A slope factor is an upper bound, approximating a 95% confidence limit, on the increased cancer risk from a lifetime exposure to an agent by ingestion or inhalation. This estimate, usually expressed in units of proportion affected per mg of substance/kg body weight-day, is generally reserved for use in the low-dose region of the dose-response relationship, that is, for exposures corresponding to risks less than 1 in 100.
Slope factors are also referred to as cancer potency factors (PF).
4-Methylimidazole is a heterocyclic organic chemical compound with molecular formula H
3C–C
3H
3N
2 or C
4H
6N
2. It is formally derived from imidazole through replacement of the hydrogen in position 4 by a methyl group. It is a slightly yellowish solid.
Exposure to ionizing radiation is known to increase the future incidence of cancer, particularly leukemia. The mechanism by which this occurs is well understood, but quantitative models predicting the level of risk remain controversial. The most widely accepted model posits that the incidence of cancers due to ionizing radiation increases linearly with effective radiation dose at a rate of 5.5% per sievert; if correct, natural background radiation is the most hazardous source of radiation to general public health, followed by medical imaging as a close second. Additionally, the vast majority of non-invasive cancers are non-melanoma skin cancers caused by ultraviolet radiation. Non-ionizing radio frequency radiation from mobile phones, electric power transmission, and other similar sources have been described as a possible carcinogen by the WHO's International Agency for Research on Cancer, but the link remains unproven.
Threshold dose is the minimum dose of drug that triggers minimal detectable biological effect in an animal. At extremely low doses, biological responses are absent for some of the drugs. The increase in dose above threshold dose induces an increase in the percentage of biological responses. Several benchmarks have been established to describe the effects of a particular dose of drug in a particular species, such as NOEL(no-observed-effect-level), NOAEL(no-observed-adverse-effect-level) and LOAEL(lowest-observed-adverse-effect-level). They are established by reviewing the available studies and animal studies. The application of threshold dose in risk assessment safeguards the participants in human clinical trials and evaluates the risks of chronic exposure to certain substances. However, the nature of animal studies also limits the applicability of experimental results in the human population and its significance in evaluating potential risk of certain substances. In toxicology, there are some other safety factors including LD50, LC50 and EC50.
References
- ↑ Derelanko, M.J. and Hollinger, M.A. (Eds). CRC Handbook of Toxicology. 1995. CRC Press. Boca Raton, FL.
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