Lethality (also called deadliness or perniciousness) is how capable something is of causing

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

. Most often it is used when referring to diseases,

chemical weapons A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...

biological weapons A biological agent (also called bio-agent, biological threat agent, biological warfare agent, biological weapon, or bioweapon) is a bacterium, virus, protozoan, parasite, fungus, or toxin that can be used purposefully as a weapon in bioterrorism ...

, or their

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subs ...

chemical components. The use of this term denotes the ability of these weapons to kill, but also the possibility that they may not kill. Reasons for the lethality of a weapon to be inconsistent, or expressed by percentage, can be as varied as minimized exposure to the weapon, previous exposure to the weapon minimizing susceptibility, degradation of the weapon over time and/or distance, and incorrect deployment of a multi-component weapon. This term can also refer to the after-effects of weapon use, such as

nuclear fallout Nuclear fallout is the residual radioactive material propelled into the upper atmosphere following a nuclear blast, so called because it "falls out" of the sky after the explosion and the shock wave has passed. It commonly refers to the radioac ...

, which has highest lethality nearest the deployment site, and in proportion to the subject's size and nature; e.g. a child or small animal. Lethality can also refer to the after-effects of a chemical explosion. A lethality curve can be developed for process safety reasons to protect people and equipment. The impact is typically greatest closest to the explosion site and lessens to the outskirts of the impact zone. Pressure, toxicity and location affect the lethality. Lethality is also a term used by microbiologists and

food scientist Food science is the basic science and applied science of food; its scope starts at overlap with agricultural science and nutritional science and leads through the scientific aspects of food safety and food processing, informing the development ...

s as a measure of the ability of a process to destroy bacteria. Lethality may be determined by enumeration of survivors after incremental exposures.

See also