Acute toxicity describes the adverse effects of a substance that 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

Chronic toxicity

Chronic toxicity is a property of a substance that has toxic effects on a living organism, when that organism is exposed to the substance continuously or repeatedly. Compared with acute toxicity.Two distinct situations need to be considered:...

, 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 widely considered unethical to use humans as test subjects for acute (or chronic) toxicity research. However, some information can be gained from investigating accidental human exposures (e.g., factory accidents). Otherwise, most acute toxicity data comes from animal testing

Animal testing

Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments. Worldwide it is estimated that the number of vertebrate animals—from zebrafish to non-human primates—ranges from the tens of millions to more than 100 million...

 or, more recently, in vitro

In vitro

In vitro refers to studies in experimental biology that are conducted using components of an organism that have been isolated from their usual biological context in order to permit a more detailed or more convenient analysis than can be done with whole organisms. Colloquially, these experiments...

testing methods and inference

Statistical inference

In statistics, statistical inference is the process of drawing conclusions from data that are subject to random variation, for example, observational errors or sampling variation...

 from data on similar substances.

Regulatory values

Limits for short-term exposure, such as STELs or CVs, are defined only if there is a particular acute toxicity associated with a substance.

• Short-Term Exposure Limit
  Short-term exposure limit
  The short-term exposure limit is a term used in occupational health, industrial hygiene and toxicology. The STEL may be a legal limit in the United States for exposure of an employee to a chemical substance. The Occupational Safety and Health Administration has set OSHA-STELs for 1,3-Butadiene,...
  
  , 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, LC_min; Mimimum lethal dose, LD_min
• Median lethal concentration, LC₅₀; Median lethal dose, LD₅₀; Median lethal time, LT₅₀
• Absolute lethal concentration, LC₁₀₀; Absolute lethal dose, LD₁₀₀