Title: lowest-observed-effect concentration
Long Title: IUPAC Gold Book - lowest-observed-effect concentration
DOI: 10.1351/goldbook.14820
Status: current

Definition
Lowest concentration of a material used in an aquatic toxicity test that has a statistically significant adverse effect on the exposed population of test organisms compared with controls.

Note
When derived from a life cycle or partial life cycle test, it is numerically the same as the upper limit of the maximum acceptable toxicant concentration (MATC). Also called lowest-observed-adverse-effect level (LOAEL).

Related Terms
- maximum acceptable toxicant concentration: https://goldbook.iupac.org//terms/view/14832
- population: https://goldbook.iupac.org//terms/view/14932

Source
- PAC, 2009, 81, 829. 'Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)' on page 908 (https://doi.org/10.1351/PAC-REC-08-07-09)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/14820/html
- json: https://goldbook.iupac.org/terms/view/14820/json
- xml: https://goldbook.iupac.org/terms/view/14820/xml

Citation: Citation: 'lowest-observed-effect concentration' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.14820
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Disclaimer: The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.
Accessed: 2026-04-20T21:23:22+00:00