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Toxicology (from the Greek words τοξικός - toxicos "poisonous" and logos) is the study of the adverse effects of chemicals on living organisms.[1] It is the study of symptoms, mechanisms, treatments and detection of poisoning, especially the poisoning of people.

Contents

History

Mathieu Orfila is considered to be the modern father of toxicology, having given the subject its first formal treatment in 1813 in his Traité des poisons, also called Toxicologie générale.[2]

Theophrastus Phillipus Auroleus Bombastus von Hohenheim (1493–1541) (also referred to as Paracelsus, from his belief that his studies were above or beyond the work of Celsus - a Roman physician from the first century) is also considered "the father" of toxicology.[3] He is credited with the classic toxicology maxim, "Alle Dinge sind Gift und nichts ist ohne Gift; allein die Dosis macht, dass ein Ding kein Gift ist." which translates as, "All things are poison and nothing is without poison; only the dose makes a thing not a poison." This is often condensed to: "The dose makes the poison".

An even earlier writer on toxicology was Ibn Wahshiya (Arabic: أبو بكر أحمد بن وحشية Abu Bakr Ahmed ibn Wahshiyah ), who wrote the Book on Poisons in the 9th or 10th century.[4]

The relationship between dose and its effects on the exposed organism is of high significance in toxicology. The chief criterion regarding the toxicity of a chemical is the dose, i.e. the amount of exposure to the substance. All substances are toxic under the right conditions. The term LD50 refers to the dose of a toxic substance that kills 50 percent of a test population (typically rats or other surrogates when the test concerns human toxicity). LD50 estimations in animals are no longer required for regulatory submissions as a part of pre-clinical development package.[citation needed]

The conventional relationship (more exposure equals higher risk) has been challenged in the study of endocrine disruptors.

Toxicity of metabolites

Many substances regarded as poisons are toxic only indirectly. An example is "wood alcohol," or methanol, which is chemically converted to formaldehyde and formic acid in the liver. It is the formaldehyde and formic acid that cause the toxic effects of methanol exposure. As for drugs, many small molecules are made toxic in the liver, a good example being acetaminophen (paracetamol), especially in the presence of chronic alcohol use. The genetic variability of certain liver enzymes makes the toxicity of many compounds differ between one individual and the next. Because demands placed on one liver enzyme can induce activity in another, many molecules become toxic only in combination with others. A family of activities that many toxicologists engage includes identifying which liver enzymes convert a molecule into a poison, what are the toxic products of the conversion and under what conditions and in which individuals this conversion takes place.

Subdisciplines of toxicology

There are various specialized subdisciplines within the field of toxicology that concern diverse chemical and biological aspects of this area. For example, toxicogenomics involves applying molecular profiling approaches to the study of toxicology.[5] Other areas include Aquatic toxicology, Chemical toxicology, Ecotoxicology, Environmental toxicology, Forensic toxicology, and Medical toxicology.

Chemical toxicology

Chemical toxicology is a scientific discipline involving the study of structure and mechanism related to the toxic effects of chemical agents, and encompasses technology advances in research related to chemical aspects of toxicology. Research in this area is strongly multidisciplinary, spanning computational chemistry and synthetic chemistry, proteomics and metabolomics, drug discovery, drug metabolism and mechanisms of action, bioinformatics, bioanalytical chemistry, chemical biology, and molecular epidemiology.

See also

References

  1. ^ "What is Toxicology" -Schrager, TF, October 4, 2006
  2. ^ U.S. National Library of Medicine, Biography of Mathieu Joseph Bonaventure Orfila (1787–1853)
  3. ^ Paracelsus Dose Response in the Handbook of Pesticide Toxicology WILLIAM C KRIEGER / Academic Press Oct01
  4. ^ Martin Levey (1966), Medieval Arabic Toxicology: The Book on Poisons of ibn Wahshiya and its Relation to Early Native American and Greek Texts
  5. ^ Afshari CA, Hamadeh HK (2004). Toxicogenomics: principles and applications. New York: Wiley-Liss. ISBN 0-471-43417-5. 
    Review: Omenn GS (November 2004). "Toxicogenomics: Principles and Applications". Environ Health Perspect 112 (16): A962. 

Further reading

  • Nelson, Lewis H.; Flomenbaum, Neal; Goldfrank, Lewis R.; Hoffman, Robert Louis; Howland, Mary Deems; Neal A. Lewin (2006). Goldfrank's toxicologic emergencies. New York: McGraw-Hill, Medical Pub. Division. ISBN 0-07-147914-7. 
  • Richards IS. 2008. Principles and Practice of Toxicology in Public Health. Jones and Bartlett Publisher, Sudbury Massachusetts.

External links

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1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

Medical warning!
This article is from the 1911 Encyclopaedia Britannica. Medical science has made many leaps forward since it has been written. This is not a site for medical advice, when you need information on a medical condition, consult a professional instead.

TOXICOLOGY, the name of that branch of science which deals with poisons, their effects and antidotes, &c. For the general treatment of the subject and for the law relating to the sale thereof see Poisons, and for the criminal law see Medical Jurisprudence. The term "toxic," meaning poisonous, is derived from Gr. Toov, bow, owing to the custom of smearing arrows with poison.


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Wikibooks

Up to date as of January 23, 2010

From Wikibooks, the open-content textbooks collection

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Simple English

Toxicology is the study of the negative effects of chemicals on living things. The main factor in the toxicity of a substance is the dose (how much of the chemical has been given), as almost all substances can be toxic under the right conditions.

Many chemicals that we call poisons are only toxic when made into different chemicals by the body. Many chemicals are made toxic in the liver by enzymes, for example paracetamol, which is a common drug. There is also some variation in liver enzymes (caused by genetic variation) in different people that can cause a substance to be more toxic in one person than it is in another. Some substances are also only toxic when they are with other chemicals, as one liver enzyme can cause activity in another enzyme.

Some measures of toxicity

  • LD50 is a test that finds an average dose required to kill half of the animals being tested (normally rats in human toxicity).
  • The Fixed Dose Procedure, an alternative to the LD50 which measures oral toxicity in a similar way, but using fewer animals and with less suffering.
  • Minimum lethal dose (MLD, also LDmin), the smallest amount of drug that can produce death in an animal species under controlled conditions.
  • Draize test
  • LDLo
  • IC50
  • EC50

Other pages

  • In vitro toxicology
  • Toxicity

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