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A toxin is a naturally occurring

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

poison Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...

produced by

metabolic activities Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

of living cells or organisms. They occur especially as

proteins Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919) and is derived from the word " toxic". Toxins can be small molecules, peptides, or proteins that are capable of causing disease on contact with or absorption by body tissues interacting with biological

macromolecule A macromolecule is a very large molecule important to biophysical processes, such as a protein or nucleic acid. It is composed of thousands of covalently bonded atoms. Many macromolecules are polymers of smaller molecules called monomers. The ...

s such as enzymes or

cellular receptors In biochemistry and pharmacology, receptors are chemical structures, composed of protein, that receive and transduce signals that may be integrated into biological systems. These signals are typically chemical messengers which bind to a recepto ...

. They vary greatly in their toxicity, ranging from usually minor (such as a

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyly, monophyletic lineage within the ...

sting Sting may refer to: * Stinger or sting, a structure of an animal to inject venom, or the injury produced by a stinger * Irritating hairs or prickles of a stinging plant, or the plant itself Fictional characters and entities * Sting (Middle-eart ...

) to potentially fatal even at extremely low doses (such as

botulinum toxin Botulinum toxin, or botulinum neurotoxin (BoNT), is a neurotoxic protein produced by the bacterium ''Clostridium botulinum'' and related species. It prevents the release of the neurotransmitter acetylcholine from axon endings at the neuromusc ...

Terminology

Toxins are often distinguished from other chemical agents strictly based on their biological origin. Less strict understandings embrace naturally occurring non-organic toxins, such as arsenic. Other understandings embrace synthetic analogs of naturally occurring organic poisons as toxins, and may or may not embrace naturally occurring non-organic poisons. It is important to confirm usage if a common understanding is critical. Toxins are a subset of toxicants. The term toxicant is preferred when the poison is man-made and therefore artificial. The human and scientific genetic assembly of a natural-based toxin should be considered a toxin as it is identical to its natural counterpart. The debate is one of linguistic semantics. The word toxin does not specify method of delivery (as opposed to venom, a toxin delivered via a bite, sting, etc.).

Poison Poison is a chemical substance that has a detrimental effect to life. The term is used in a wide range of scientific fields and industries, where it is often specifically defined. It may also be applied colloquially or figuratively, with a broa ...

is a related but broader term that encompasses both toxins and toxicants; poisons may enter the body through any means - typically

inhalation Inhalation (or Inspiration) happens when air or other gases enter the lungs. Inhalation of air Inhalation of air, as part of the cycle of breathing, is a vital process for all human life. The process is autonomic (though there are exceptions ...

, ingestion, or skin absorption. Toxin, toxicant, and poison are often used interchangeably despite these subtle differences in definition. The term toxungen has also been proposed to refer to toxins that are delivered onto the body surface of another organism without an accompanying

wound A wound is a rapid onset of injury that involves laceration, lacerated or puncture wound, punctured skin (an ''open'' wound), or a bruise, contusion (a ''closed'' wound) from blunt force physical trauma, trauma or compression. In pathology, a '' ...

. A rather informal terminology of individual toxins relates them to the anatomical location where their effects are most notable: * Genitotoxin, damages the urinary organs or the reproductive organs * Hemotoxin, causes destruction of

red blood cells Red blood cells (RBCs), also referred to as red cells, red blood corpuscles (in humans or other animals not having nucleus in red blood cells), haematids, erythroid cells or erythrocytes (from Greek language, Greek ''erythros'' for "red" and ''k ...

( hemolysis) *

Phototoxin Phototoxins are toxins that can cause allergic reactions in particularly susceptible individuals and which can cause dangerous photosensitivity in a much broader range of subjects. Phototoxins are common in: *a variety of plants (including food pla ...

, causes dangerous photosensitivity * Hepatotoxins affect the liver *

Neurotoxin Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature ner ...

s affect the nervous system On a broader scale, toxins may be classified as either

exotoxin An exotoxin is a toxin secreted by bacteria. An exotoxin can cause damage to the host by destroying cells or disrupting normal cellular metabolism. They are highly potent and can cause major damage to the host. Exotoxins may be secreted, or, simi ...

s, excreted by an organism, or endotoxins, which are released mainly when bacteria are lysed.

Biological

The term "biotoxin" is sometimes used to explicitly confirm the biological origin as opposed to environmental or anthropogenic origins. Biotoxins can be classified by their mechanism of delivery as

s (passively transferred via ingestion, inhalation, or absorption across the skin), toxungens (actively transferred to the target's surface by spitting, spraying, or smearing), or venoms (delivered through a wound generated by a bite, sting, or other such action). They can also be classified by their source, such as fungal biotoxins,

microbial toxin Microbial toxins are toxins produced by micro-organisms, including bacteria, fungi, protozoa, dinoflagellates, and viruses. Many microbial toxins promote infection and disease by directly damaging host tissues and by disabling the immune system. ...

s, plant biotoxins, or animal biotoxins. Toxins produced by microorganisms are important virulence determinants responsible for microbial pathogenicity and/or evasion of the host immune response. Biotoxins vary greatly in purpose and mechanism, and can be highly complex (the venom of the cone snail can contain over 100 unique peptides, which target specific nerve channels or receptors). Biotoxins in nature have two primary functions: * Predation, such as in the spider, snake, scorpion, jellyfish, and wasp * Defense as in the

, ant, termite, honey bee, wasp,

poison dart frog Poison dart frog (also known as dart-poison frog, poison frog or formerly known as poison arrow frog) is the common name of a group of frogs in the family Dendrobatidae which are native to tropical Central and South America. These species are ...

and plants producing toxins ** The toxins used as defense in species among the

can also be used for medicinal purposes Some of the more well known types of biotoxins include: * Cyanotoxins, produced by

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

Dinotoxin Dinotoxins are a group of toxins which are produced by flagellate, aquatic, unicellular protists called dinoflagellates. Dinotoxin was coined by Hardy and Wallace in 2012 as a general term for the variety of toxins produced by dinoflagellates. Dinof ...

s, produced by

dinoflagellate The dinoflagellates (Greek δῖνος ''dinos'' "whirling" and Latin ''flagellum'' "whip, scourge") are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered algae. Dinoflagellates are ...

s * Necrotoxins cause

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

(i.e., death) in the cells they encounter. Necrotoxins spread through the bloodstream. In humans, skin and

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

tissues are most sensitive to necrotoxins. Organisms that possess necrotoxins include: ** The

brown recluse The brown recluse (''Loxosceles reclusa''), Sicariidae (formerly placed in a family "Loxoscelidae") is a recluse spider with Necrosis, necrotic venom. Similar to those of other recluse spiders, their bites sometimes require medical attention. T ...

or "fiddle back" spider ** Most

rattlesnake Rattlesnakes are venomous snakes that form the genera ''Crotalus'' and ''Sistrurus'' of the subfamily Crotalinae (the pit vipers). All rattlesnakes are vipers. Rattlesnakes are predators that live in a wide array of habitats, hunting small anim ...

s and vipers produce phospholipase and various trypsin-like serine proteases ** Puff adder ** Necrotizing fasciitis (caused by the "flesh eating" bacterium '' Streptococcus pyogenes'') – produces a pore forming toxin *

s primarily affect the nervous systems of animals. The group neurotoxins generally consists of ion channel toxins that disrupt ion channel conductance. Organisms that possess neurotoxins include: ** The

black widow Black widow may refer to: Spiders * Black widow spider, a common name for some species of spiders in the genus ''Latrodectus'' American species * ''Latrodectus apicalis'', the Galapagos black widow * ''Latrodectus curacaviensis'', the South Amer ...

spider. ** Most scorpions ** The box jellyfish ** Elapid snakes ** The cone snail ** The Blue-ringed octopus ** Venomous fish ** Frogs ** '' Palythoa'' coral ** Various different types of

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

and dinoflagellates * Myotoxins are small, basic peptides found in snake and

lizard Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia alt ...

venoms, They cause muscle tissue damage by a non-enzymatic receptor based mechanism. Organisms that possess myotoxins include: **

s ** Mexican beaded lizard * Cytotoxins are toxic at the level of individual cells, either in a non-specific fashion or only in certain types of living cells: **

Ricin Ricin ( ) is a lectin (a carbohydrate-binding protein) and a highly potent toxin produced in the seeds of the castor oil plant, ''Ricinus communis''. The median lethal dose (LD50) of ricin for mice is around 22 micrograms per kilogram of body ...

, from castor beans **

Apitoxin Apitoxin or bee venom is the venom produced by the honey bee. It is a cytotoxic and hemotoxic bitter colorless liquid containing proteins, which may produce local inflammation. It may have similarities to sea nettle toxin. Components Bee venom i ...

, from honey bees ** T-2 mycotoxin, from certain toxic mushrooms ** Cardiotoxin III, from Chinese cobra ** Hemotoxin, from

viper The Viperidae (vipers) are a family of snakes found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, and various other isolated islands. They are venomous and have long (relative to non-vipers), hinged fangs tha ...

Weaponry

Many living organisms employ toxins offensively or defensively. A relatively small number of toxins are known to have the potential to cause widespread sickness or casualties, but these may be appealing to those who would use them nefariously for several reasons. They are often inexpensive and easily available, and in some cases it is possible to refine them outside the laboratory. As biotoxins act quickly, and are highly toxic even at low doses, they can be more efficient than chemical agents. Due to these factors, it is vital to raise awareness of the clinical symptoms of biotoxin poisoning, and to develop effective countermeasures including rapid investigation, response, and treatment.

Environmental

The term "environmental toxin" can sometimes explicitly include synthetic contaminants such as industrial pollutants and other artificially made toxic substances. As this contradicts most formal definitions of the term "toxin", it is important to confirm what the researcher means when encountering the term outside of microbiological contexts. Environmental toxins from food chains that may be dangerous to human health include: * Paralytic shellfish poisoning (PSP) * Amnesic shellfish poisoning (ASP) * Diarrheal shellfish poisoning (DSP) * Neurotoxic shellfish poisoning (NSP)

Research

In general, when scientists determine the amount of a substance that may be hazardous for humans, animals and/or the environment they determine the amount of the substance likely to trigger effects and if possible establish a safe level. In Europe, the European Food Safety Authority produced risk assessments for more than 4,000 substances in over 1,600 scientific opinions and they provide open access summaries of human health, animal health and ecological hazard assessments in their OpenFoodTox database. The OpenFoodTox database can be used to screen potential new foods for toxicity. The Toxicology and Environmental Health Information Program (TEHIP) at the United States National Library of Medicine (NLM) maintains a comprehensive toxicology and environmental health web site that includes access to toxins-related resources produced by TEHIP and by other government agencies and organizations. This web site includes links to databases, bibliographies, tutorials, and other scientific and consumer-oriented resources. TEHIP also is responsible for the Toxicology Data Network (TOXNET), an integrated system of toxicology and environmental health databases that are available free of charge on the web. TOXMAP is a Geographic Information System (GIS) that is part of TOXNET. TOXMAP uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory and Superfund Basic Research Programs.

References

External links

T3DB: Toxin-target databaseATDB: Animal toxin databaseSociety of ToxicologyThe Journal of Venomous Animals and Toxins including Tropical DiseasesToxSeek: Meta-search engine in toxicology and environmental healthWebsite on Models & Ecotoxicology
{{Toxicology * Biology terminology * Chemical ecology