Lethal Dose 50: A single dose of a material that, on the basis of laboratory tests, is expected to kill 50% of a group of test animals.
The LD50 dose is usually expressed as milligrams or grams of material per kilogram of animal weight (mg/kg or g/kg)
LD stands for "Lethal Dose". LD50 is the amount of a material, given all at once, which causes the death of 50% (one half) of a group of test animals.
The LD50 is one way to measure the short-term poisoning potential (acute toxicity) of a material.
Toxicologists can use many kinds of animals but most often testing is done with rats and mice.
It is usually expressed as the amount of chemical administered (e.g., milligrams) per 100 grams (or kilogram) of the body weight of the test animal.
The LD50 can be found for any route of entry or administration but dermal (applied to the skin) and oral (given by mouth) administration methods are the most common.
Lethal Concentration 50: The concentration of a material in air that, on the basis of laboratory tests, is expected to kill 50% of a group of test animals when administered as a single exposure (usually 1 or 4 hours).
The LC50 is expressed as parts of material per million parts of air, by volume (ppm) for gases and vapors, or as micrograms of material per liter of air (µg/L) or milligrams of material per cubic meter of air (mg/m3) for dusts and mists, as well as for gases and vapors.
LC stands for "Lethal Concentration". LC values usually refer to the concentration of a chemical in air but in environmental studies it can also mean the concentration of a chemical in water.
For inhalation experiments, the concentration of the chemical in air that kills 50% of the test animals in a given time (usually four hours) is the LC50 value
Lethal dose for 1% of the animal test population
Lethal dose for 100% of the animal test population
The lowest dose causing lethality
The lowest dose causing a toxic effect
Acute toxicity is the ability of a chemical to cause ill effects relatively soon after one oral administration or a 4-hour exposure to a chemical in air.
"Relatively soon" is usually defined as a period of minutes, hours (up to 24) or days (up to about 2 weeks) but rarely longer.
Canadian Center for Occupational Health and Safety.