Editing Toxicity (section)

==Types==

There are generally five types of toxicities: chemical, biological, physical, radioactive and behavioural.

Disease-causing microorganisms and parasites are toxic in a broad sense but are generally called [[pathogen]]s rather than toxicants. The biological toxicity of pathogens can be difficult to measure because the [[threshold dose]] may be a single organism. Theoretically one [[virus]], bacterium or [[worm]] can reproduce to cause a serious [[infection]]. If a host has an intact [[immune system]], the inherent toxicity of the organism is balanced by the host's response; the effective toxicity is then a combination. In some cases, e.g. [[cholera toxin]], the disease is chiefly caused by a nonliving substance secreted by the organism, rather than the organism itself. Such nonliving biological toxicants are generally called [[toxin]]s if produced by a microorganism, plant, or fungus, and [[venom]]s if produced by an animal.

Physical toxicants are substances that, due to their physical nature, interfere with biological processes. Examples include [[coal]] dust, [[asbestos]] fibres or finely divided [[silicon dioxide]], all of which can ultimately be fatal if inhaled. Corrosive chemicals possess physical toxicity because they destroy tissues, but are not directly poisonous unless they interfere directly with biological activity. [[Water intoxication|Water can act as a physical toxicant]] if taken in extremely high doses because the concentration of vital ions decreases dramatically with too much water in the body. Asphyxiant gases can be considered physical toxicants because they act by displacing oxygen in the environment but they are inert, not chemically toxic gases.

Radiation can have a toxic effect on organisms.<ref>{{cite journal | doi=10.1016/j.taap.2003.08.019 | volume=195 | issue=3 | title=Toxic effects of ultraviolet radiation on the skin | journal=Toxicology and Applied Pharmacology | pages=298–308 | pmid=15020192 | date=March 2005 | vauthors=Matsumura Y, Ananthaswamy HN}}</ref>

Behavioral toxicity refers to the undesirable effects of essentially therapeutic levels of medication clinically indicated for a given disorder (DiMascio, Soltys and Shader, 1970). These undesirable effects include anticholinergic effects, alpha-adrenergic blockade, and dopaminergic effects, among others.<ref>{{cite book |doi=10.1016/B0080-4270(73)00116-4 |chapter=Pharmacological Therapies |title=Comprehensive Clinical Psychology |date=1998 |last1=Singh |first1=Nirbhay N. |last2=Ellis |first2=Cynthia R. |pages=267–293 |isbn=978-0-08-042707-2 }}</ref>