Poison

:This article is about the dangerous substance. For the band see Poison.

Classification of biological poisons by mechanism

Corrosives

Corrosives mechanically damage biological systems on contact. Both the sensation and injury caused by contact with a corrosive resembles a burn injury.

Related Topics:
Corrosive - Burn injury

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Acids

Strong inorganic acids, such as concentrated sulfuric acid, nitric acid or hydrochloric acid, destroy any biological tissue with which they come in contact within seconds.

Related Topics:
Sulfuric acid - Nitric acid - Hydrochloric acid - Biological tissue

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Bases

Strong inorganic bases, such as lye, gradually dissolve skin on contact but can cause serious damage to eyes or mucous membranes much more rapidly. Ammonia is a far weaker base than lye, but has the distinction of being a gas and thus may more easily come into contact with the sensitive mucous membranes of the respiratory system. Quicklime, which has household uses, is a particularly common cause of poisoning. Some of the light metals, if handled carelessly, can not only cause thermal burns, but also produce very strongly basic solutions in sweat.

Related Topics:
Lye - Mucous membrane - Ammonia - Respiratory system - Quicklime

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Oxidizers

Poisons of this class are generally not very harmful to higher life forms such as humans (for whom the outer layer of cells are more or less disposable), but lethal to microorganisms such as bacteria. Typical examples are ozone and chlorine, either of which is added to nearly every municipal water supply in order to kill any harmful microorganisms present.

Related Topics:
Microorganism - Bacteria - Ozone - Chlorine - Municipal water supply

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All halogens are strong oxidizing agents, fluorine being the strongest of all.

Related Topics:
Halogen - Oxidizing agent - Fluorine

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:See also: Free radical

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Reducing agents

The most notable substance in this class is phosphorus.

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Metabolic poisons (energy)

Metabolic poisons act by adversely disrupting the normal metabolism of an organism.

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Specific biochemical inhibitors

• By far the most notable substance in this class is carbon monoxide, which blocks the ability of red blood cells to transport oxygen.
• Fluoroacetate blocks a vital step in the citric acid cycle.
• Cyanide bonds with an enzyme involved in ATP production.
• Rotenone - disrupts electron transport in cellular respiration
• Antimycin - disrupts electron transport in cellular respiration
• Malonate - inhibits cellular respiration
• 2,4-Dinitrophenol - disrupts cellular proton gradient

Heavy metals

A common trait shared by heavy metals is the chronic nature of their toxicity (a notable exception would be bismuth, which is considered entirely non-toxic). Low levels of heavy metal salts ingested over time accumulate in the body until toxic levels are reached.

Related Topics:
Heavy metal - Bismuth

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Heavy metals are generally far more toxic when ingested in the form of soluble salts than in elemental form. For example, metallic mercury passes through the human digestive tract without interaction and is commonly used in dental fillings—even though mercury salts and inhaled mercury vapor are highly toxic.

Related Topics:
Soluble salt - Mercury - Dental fillings - Mercury salts

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Notable examples:

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• arsenic (see arsenic poisoning)
• antimony
• barium
• cadmium
• chromium
• lead
• mercury
• thallium
• uranium
• beryllium (a highly but subtly toxic light metal)

Neurotoxins

Neurotoxins interfere with nervous system functions and often lead to near-instant paralysis followed by rapid death. They include most spider and snake venoms, as well as many modern chemical weapons. One class of toxins of interest to neurochemical researchers are the various cone snail toxins known as conotoxins.

Related Topics:
Neurotoxin - Nervous system - Paralysis - Death - Spider - Snake - Chemical weapon - Cone snail - Conotoxin

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Anticholinesterases

• Fasciculin

Acetylcholine antagonists

• Curare
• Pancuronium

Cell membrane disrupters

Others

• Nicotine - not strictly a neurotoxin, but capable in large doses of causing heart attack

Teratogens (birth defects)

• Thalidomide

Mutagens (DNA damage)

• Ultraviolet Rays - Long term exposure may cause skin cancer such as Melanoma
• Other Ionizing Radiation - Causes radiation sickness and cancer
• ethidium bromide

Carcinogens (cancer)

A carcinogen is a chemical substance which is believed to cause cancer. There are an enormous variety of possible carcinogens. Some of the better known or more controversial examples are listed below.

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• Some artificial sweeteners (e.g. Aspartame and Saccharin) have been alleged to be carcinogenic or neurotoxic (however these research behind these claims is highly controversial and inconclusive; the FDA believes aspartame is safe for humans in dietary doses).
• Asbestos - a widely used insulating material that causes mesothelioma and other cancers especially in the respiratory tract.
• Benzene (lab solvent, used in various chemical reactions).
• Carbon tetrachloride (formerly used in fire extinguishers).
• Dioxin - actually a group of many chemicals - has carcinogenic and other toxic effects.