No-observed-adverse-effect level
No-observed-adverse-effect level (NOAEL) is a term used in toxicology and pharmacology to denote the highest experimental point that does not cause a harmful effect in test subjects after exposure.
Pronunciation
The term is pronounced as "no-observed-adverse-effect level".
Etymology
The term is derived from the field of toxicology, where it is used to describe the highest dose of a substance that does not cause adverse effects in test subjects.
Definition
The No-observed-adverse-effect level (NOAEL) is the highest dose of a substance that, when administered under defined conditions, results in no statistically or biologically significant increases in the frequency or severity of any adverse effects in the exposed population when compared with its appropriate control group.
Related Terms
- Lowest-observed-adverse-effect level (LOAEL)
- Maximum tolerated dose (MTD)
- Therapeutic index (TI)
- Lethal dose, 50 percent (LD50)
Use in Risk Assessment
In risk assessment, the NOAEL is used to derive the acceptable daily intake (ADI) or reference dose (RfD). The NOAEL is divided by a safety factor, usually 100, to account for uncertainties in the extrapolation from experimental animals to humans and for variations in human susceptibility.
See Also
External links
- Medical encyclopedia article on No-observed-adverse-effect level
- Wikipedia's article - No-observed-adverse-effect level
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