Glossary / Toxicology
NOAEL
NOAEL, the No Observed Adverse Effect Level, is the highest dose or exposure in a toxicity study at which no statistically or biologically significant harmful effect is seen in the exposed group compared with controls.
Explanation
A NOAEL comes from studies where groups of animals receive several dose levels over days, weeks or longer. The highest level that produced no harmful effect becomes the NOAEL. Doses above it begin to cause measurable harm. It is therefore a study result, tied to a species, route, duration and effect.
Regulators use the NOAEL as a starting point to estimate safe human exposure. They divide it by uncertainty factors that allow for differences between animals and people and between individual humans. The results are values such as reference doses, and in Europe derived no-effect levels such as the DNEL. Occupational exposure limits may also draw on NOAEL findings.
The NOAEL has weaknesses. It can only be one of the doses the researchers happened to test, so a study with few dose groups gives a poor picture. Small studies may also miss real effects, which makes the NOAEL look safer than it is. Because of this, LOAEL and other methods are used alongside it.
The SDS rarely reports the NOAEL as a safe level for workers. It provides it as supporting data on how doses relate to effects.
What to do and watch for
- Remember a NOAEL applies to specific conditions and endpoints, not to all possible effects.
- Never treat a reported NOAEL as a safe workplace exposure.
- Use the SDS and applicable exposure limits to set controls.
Where it appears on an SDS
- Section 11: Toxicological information. Repeated-dose or reproductive study entries sometimes state the NOAEL with species, route, duration and the effect examined.
- Section 12: Ecological information. Ecotoxicity entries may give a NOAEC or NOEC, the environmental equivalent from long-term aquatic tests.
SDS content and wording vary by supplier. This page is general reference and does not replace the current SDS for your product.