LOAELNOAEL

LOAEL and NOAEL are terms used in toxicology and risk assessment to describe dose levels related to adverse effects. LOAEL stands for the lowest observed adverse effect level, the smallest dose in a study at which a measured adverse effect is observed. NOAEL stands for the no observed adverse effect level, the highest dose at which no adverse effects are observed. The term LOAELNOAEL is not a standard designation, but may be encountered as a way to describe, in a single context, the pair of values reported for a substance or study: the LOAEL and the NOAEL.

In practice, LOAELNOAEL can indicate the range between which safe exposure was not demonstrated within a particular study, or simply the two key reference points reported for a given chemical, species, endpoint, and duration. These values are used to support regulatory decisions, often by applying uncertainty factors to derive reference doses or tolerable daily intakes. It is important to note that both LOAEL and NOAEL are highly dependent on study design, including the species, endpoint selection, duration, and the spacing of dose levels.

Limitations include the fact that the LOAEL relies on tested doses and may overestimate risk if dose spacing is wide, and the NOAEL may not capture effects that occur below the tested thresholds. Modern risk assessment increasingly favors benchmark dose modeling, which uses the entire dose–response relationship to estimate a point of departure with confidence intervals, rather than relying solely on LOAEL/NOAEL values.

If encountered, LOAELNOAEL should be interpreted with context, clarifying that it refers to the reported LOAEL and NOAEL values for a specific study or dataset.