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LD50

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LDLo, Lowest Lethal Dose

Definition

• An LD_Lo value is the lowest amount of a solid or liquid material reported to have caused the death of animals or humans. The exposure may be acute or chronic. This is also called the lowest dosage causing death, lowest detected lethal dose, and lethal dose low.

  LD_Lo is closely related to the LD₅₀ value which is the dosage which kills half of the test animals under controlled conditions.

  LC_Lo (lowest lethal concentration) is a related term used for gases, dusts, vapors, mists etc.

Additional Info



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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.

Both LD₅₀ and LD_Lo 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 unambiguously linked to a single human death even at very high levels of acute (short term) exposure; note, however they are listed by IARC as "known human carcinogens". 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 LD_Lo 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 LD_Lo dose of a hazardous chemical -- by definition, there is a resonable chance of dying!

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



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• 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 Ag 101 entry on LD50.
• 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.

Additional definitions from Google and OneLook.

Entry last updated: Saturday, June 11, 2016. This page is copyright 2000-2016 by ILPI. Unauthorized duplication or posting on other web sites is expressly prohibited. Send suggestions, comments, and new entry desires (include the URL if applicable) to us by email.

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