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LC50

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LCLo, Lowest Lethal Concentration

Definition

• An LC_Lo value is the lowest concentration of a material in air reported to have caused the death of animals or humans. The exposure may be acute or chronic. This is also called the lowest concentration causing death, lowest detected lethal concentration, and lethal concentration low.

  LC_Lo is closely related to the LC₅₀ value which is the concentration which kills half of the test animals under controlled conditions.

  This value applies to vapors, dusts, mists and gases. Solids and liquids use the closely related LD_Lo value for routes other than inhalation.

Additional Info

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Both LC50 and LCLo 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 LCLo values are parts per million (ppm) of material in air, micrograms (10-6 = 0.000001 g) per liter of air and milligrams (10-3 = 0.001 g) per cubic meter of air (see volume units and mass units).

MSDS Relevance

Never be exposed to an LC_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

The U.S. EPA's Terminology Reference System entry on LC50 has 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. The U.S. EPA has a PC-based and Acute-to-Chronic Estimation (ACE) model and Web-based Interspecies Correlation Estimation model for risk assessment. Visit the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) for the development, review, and validation of alternative toxicological testing methods. List of highly toxic gases at Wikipedia. Try your hand at Toxic Trivia here at ILPI. See also: LD50, mus (mouse), PEL, STEL, TLV. Additional definitions from Google and OneLook.

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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.