The no-observed-adverse-effect level (NOAEL) denotes the level of exposure of an organism, found by experiment or observation, at which there is no biologically or statistically significant increase in the frequency or severity of any adverse effects of the tested protocol.
The no-observed-adverse-effect level (NOAEL) signifies the exposure level of an organism, determined through experimentation or observation, at which there is no statistically significant increase in the occurrence or severity of any adverse effects associated with the tested protocol.