The lowest-observed-adverse-effect level (LOAEL), or the lowest-observed-adverse-effect concentration (LOAEC), is the lowest concentration or amount of a substance found by experiment or observation that causes an adverse alteration of morphology, function, capacity, growth, development, or lifespan of a target organism distinguished from normal organisms of the same species under defined conditions of exposure.[1] Federal agencies use the LOAEL during risk assessment to set approval standards below this level.[2]
Hypothetical dose-response showing LOAEL
The United States Environmental Protection Agency defines LOAEL as the 'lowest level of a chemical stressor evaluated in a toxicity test that shows harmful effects on a plant or animal. While LOAELs and LOAECs are similar, they are not interchangeable. A LOAEL refers to a dose of chemical that is ingested, while a LOAEC refers to direct exposure to a chemical (e.g., through gills or the skin).[3]
^NIOSH (March 2020). NIOSH Practices in Occupational Risk Assessment. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. Publication No. 2020-106. doi:10.26616/NIOSHPUB2020106. Retrieved 18 July 2024.
