Noael

Acronym for "No Observed Adverse Effect Level". In preclinical pharmaceutical research, NOAEL is an important toxicological endpoint in the determination of toxicity.

The NOAEL defines in a given study approach the highest dose or exposure concentration of a substance at which no significantly increased adverse treatment-related findings in morphology, function, growth, development or lifespan are observed.
The NOAEL value for a substance always refers to a specific biological measurement procedure with a specific form of application and a specific animal species (often oral application in rodents) or to a defined cell culture system.

If the NOAEL cannot be determined from toxicity studies, the lowest concentration/dose tested at which adverse effects are still observed (LOAEL) shall be reported.