What is the LD50?
- Indicator of the toxicity of a substance.
- Dose of a substance that kills all exposed animals.
- Concentration of an inhaled molecule that disorients 50 bees.
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Correct answer: 1 (Indicator of the toxicity of a substance)
The median lethal dose (LD50) is a quantitative indicator of the toxicity of a substance. This indicator measures the dose of a substance that causes the death of 50% of a given animal population (often mice or rats, but it may also be bees) under precisely defined experimental conditions.
The LD50 is expressed in milligrams of active substance per kilogram of body weight. The smaller this value, the more toxic the substance. This dose is valid only for a specific animal species and a specific route of exposure in the organism during a single exposure, e.g. direct contact, ingestion, inhalation, dermal application, injection, etc.
The LD50 makes it possible to measure the toxicity of a substance and thus to establish toxicity classes:
LD50 (rat, oral) vitamin C: 11,900 mg/kg – almost non-toxic
LD50 (rat, oral) caffeine: 192 mg/kg – moderately toxic
LD50 (rat, oral) cyanide: 0.5 to 3.0 mg/kg – highly toxic
LD50 (rat, oral) botulinum toxin: 1 ng/kg – extremely toxic
By analogy, LD100 is the lethal dose that results in the death of 100% of the individuals in a given animal population under defined experimental conditions.
If the substance is inhaled, the term lethal concentration 50 (LC50 or LCt50) is used to express the concentration of the toxicant in the inhaled air that causes the death of 50% of the animals. The LC50 is expressed in mg·min/m³.
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