Toxin
|
|
A toxin, in a scientific context, is a biologically produced substance that causes injury to the health of a living thing on contact or absorption, typically by interacting with biological macromolecules such as enzymes and receptors. Toxicity may be acute (as in a bee sting), chronic (as in the Guam cycad toxin), or both.
In the context of complementary medicine the term is often used as a broader category of any harmful substance claimed to cause ill health, though mainstream scientists argue that the nature of such substances is usually unproven. Many publishers of non-technical material, such as the BBC, also follow this usage to refer to toxic substances in general, though some such as The Guardian maintain the distinction that toxins are only those produced by living organisms.
Many plants, animals and microorganisms generate natural toxins to discourage or kill predators. Animal toxins that are delivered subcutaneously (e.g. by sting or bite) are also called venom. In normal usage, a poisonous organism is one that is harmful to consume, but a venomous organism uses poison to defend itself while still alive. A single organism can be both venomous and poisonous.
When toxins are generated by bacteria, they are called toxoids. The toxins may be produced either in the living body during infection (for instance, by tetanus) or by bacteria in dead biological material. Exotoxins are secreted externally by the bacteria; Endotoxin forms part of the cell wall.
Food poisoning is a term for the broad range of illnesses that can result from eating food that is spoiled or tainted by bacterial toxins, such as Endotoxin, botulinum, and the so-called Shiga-like toxin secreted by the emergent E. coli strain E. coli O157:H7.
Naturally occurring or human-modified toxins may be intentionally released by humans in chemical warfare.
A substance is considered toxic if it contains poison or induces poisoning. The word "toxic" comes from toxikon, which meant "poison arrow" in ancient Greek.
External links
- Society of Toxicology (http://www.toxicology.org)
- Cycad toxicity (http://plantnet.rbgsyd.gov.au/PlantNet/cycad/toxic.html)
- Toxins study 'shocks' family (http://news.bbc.co.uk/1/hi/wales/mid/3719412.stm) BBC News Online, 8 October, 2004
- Toxins may pass down generations (http://news.bbc.co.uk/1/hi/health/4605847.stm) BBC News Online, 3 June, 2005
- Evidence: Detox diets: do they work? (http://www.healthwatch-uk.org/hw51.html#detox) comment on complementary usage of term, HealthWatch (http://www.healthwatch-uk.org/hw51.html) Newsletter no 51: October 2003.
- Corrections and clarifications (http://www.guardian.co.uk/corrections/story/0,,1495281,00.html), The Guardian, 30 May, 2005.fr:Toxine