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LC50

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LD50, 50% Lethal Dose

Definition

• An LD₅₀ value is the amount of a solid or liquid material that it takes to kill 50% of test animals (for example, mice or rats) in one dose.

  This is closely related to the LD_Lo value which is the lowest dosage reported to have killed animals or humans.

  LC₅₀ (50% lethal concentration) is a related term used for gases, dusts, vapors, mists etc.

Additional Info

The dose may be administered orally (by mouth), injection into various parts of the body (intraperitoneally or intravenously), or dermally (application to the skin). The value is usually reported along with the administration method.

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Both LC50 and LD50 values state the animal used in the test. This is important because animal toxicity studies do not necessarily extrapolate (extend) to humans. For example, dioxins (of Love Canal, Times Beach, Sveso and Agent Orange fame) are highly toxic to guinea pigs and ducklings at extremely low levels, but have never been conclusively linked to a single human death even at very high levels of acute (short term) exposure. However, it is best to err on the safe side when evaluating animal toxicity studies and assume that most chemicals that are toxic to animals are toxic to humans. Typical units for LD50 values are milligrams or grams of material per kilogram of body weight (mg/kg or g/kg, recall that 1 kg = 2.2 pounds).

MSDS Relevance

Never be exposed to an LD₅₀ dose of a hazardous chemical -- by definition, there is a 50% chance this will kill you...and if you survive you're not going to be in good shape.

Pay close attention to the permissible exposure level (PEL) instead. This is a more realistic determination of the maximum safe exposure to a material and is usually based on the known effects of the chemical on humans rather than laboratory animals.

Further Reading

The National Institutes of Health's Intragency Research Animal Committee's Recommendation on LD50 testing (36kB PDF file) is to replace the classical LD50 method involving ~100 animals with a modified approach. The U.S. EPA's Terminology Reference System entry on LD50 and LD50 (dermal) have detailed information including links to the U.S. Federal regulations for experimental determination of toxicity values. The Canadian Centre for Occupational Health and Safety's What is an LD50 and LC50 is quite readable. Visit the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) for the development, review, and validation of alternative toxicological testing methods. Try your hand at Toxic Trivia here at ILPI. See also: intraperitoneal, intravenous, LC50, mus (mouse), PEL, STEL, TLV.

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Disclaimer: The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.