04209 IUPAC Gold Book - no-observed-effect-level 10.1351/goldbook.N04209 N04209 current acronym: NOEL 1 Greatest concentration or amount of a substance, found by experiment or observation, that causes no alterations of morphology, functional capacity, growth, development, or life span of target organisms distinguishable from those observed in normal (control) organisms of the same species and strain under the same defined conditions of exposure. morphology https://goldbook.iupac.org//terms/view/MT07285 strain https://goldbook.iupac.org//terms/view/S06037 PAC, 1993, 65, 2003. 'Glossary for chemists of terms used in toxicology (IUPAC Recommendations 1993)' on page 2076 (https://doi.org/10.1351/pac199365092003) https://goldbook.iupac.org/terms/view/N04209/html https://goldbook.iupac.org/terms/view/N04209/json https://goldbook.iupac.org/terms/view/N04209/plain Citation: 'no-observed-effect-level' 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.N04209 The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) for individual terms. If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org . 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. 2026-04-20T23:02:54+00:00