Acute toxicity

Acute toxicity describes the adverse effects of a substance which result either from a single exposure or from multiple exposures in a short space of time (usually less than 24 hours). To be described as acute toxicity, the adverse effects should occur within 14 days of the administration of the substance.

Acute toxicity is distinguished from chronic toxicity, which describes the adverse health effects from repeated exposures, often at lower levels, to a substance over a longer time period (months or years).

It is obviously unethical to test for acute (or chronic) toxicity in humans. However, some information can be gained from investigating accidental human exposures (e.g. factory accidents). Otherwise, most acute toxicity data comes from animal testing or, more recently, in vitro testing methods and inference from data on similar substances.

Regulatory values
Limits for short-term exposure, such as STELs or CVs, are only defined if there a particular acute toxicity associated with a substance.
 * Short-term exposure limit, STEL; Threshold limit value-short-term exposure limit, TLV-STEL
 * Ceiling value, CV; Threshold limit value-ceiling, TLV-C

Experimental values

 * No observed adverse effect level, NOAEL
 * Lowest observed adverse effect level, LOAEL
 * Maximum tolerable concentration, MTC, LC0; Maximum tolerable dose, MTD, LD0
 * Minimum lethal concentration, LCmin; Mimimum lethal dose, LDmin
 * Median lethal concentration, LC50; Median lethal dose, LD50; Median lethal time, LT50
 * Absolute lethal concentration, LC100; Absolute lethal dose, LD100