Glossary / Toxicology
LC50
LC50 is the concentration of a chemical in air, or in water for aquatic tests, that is expected to kill 50 percent of a group of test animals during a stated exposure period. It is the inhalation counterpart of the LD50.
Explanation
Where LD50 measures a dose, LC50 measures how concentrated the chemical is in the surrounding medium. For inhalation tests, the animals breathe air containing the substance for a fixed time, commonly a few hours, and the concentration that kills half of them is recorded. The result depends heavily on the length of exposure, so the SDS must state the duration.
Units depend on the form of the material. Gases are usually expressed in parts per million, vapors in ppm or milligrams per liter, and dusts and mists in milligrams per liter of air. GHS sets separate inhalation acute toxicity cutoffs for each form, and the SDS applies them for you, giving H330, H331 or H332 statements.
In environmental toxicology the same idea applies to fish and other aquatic organisms in water, where LC50 over a stated period describes how toxic a substance is to aquatic life. A related value, EC50, describes effects other than death, such as immobilization.
A lower LC50 means higher toxicity. As with LD50, the number comes from animal tests and cannot be used as a safe level for people.
What to do and watch for
- Check the exposure time and species before comparing LC50 values from different sources.
- Do not use LC50 to decide what air concentration is acceptable; use exposure limits.
- Treat very low LC50 gases as needing strong ventilation, detection and emergency planning.
Where it appears on an SDS
- Section 11: Toxicological information. Inhalation LC50 values with species, duration and physical form of the test material are given.
- Section 12: Ecological information. Aquatic LC50 results for fish and other organisms are summarized in the ecotoxicity entry.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.