Lethality

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Lethality is the ability of something to cause death. It’s used for diseases, chemical or biological weapons, and their toxic parts. It describes not only how deadly something can be but also that it might not kill in every case.

Lethality can vary because of:
- how much exposure a person has
- prior exposure that reduces risk
- how the weapon degrades over time or with distance
- how a multi‑part weapon is used

The term also covers after‑effects like nuclear fallout, which is most deadly closest to where it happened; the size and type of the person matter too. It can describe the consequences of major chemical or oil/gas spills that cause a fire, explosion, or toxic cloud.

In process safety, lethality curves show how mortality changes around an accident site; death risk is usually highest near the site and falls outward. Factors include blast overpressure, heat, toxicity, and location.

In microbiology and food science, lethality means how well a process kills bacteria, usually measured by counting survivors after increasing exposure.