Lowest-observed-adverse-effect level

<p>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 <a href="/facts/Morphology_(biology)/Nl3B0myy">morphology</a>, function, capacity, growth, development, or lifespan of a target organism distinguished from normal organisms of the same species under defined conditions of exposure.  Federal agencies use the LOAEL during <a href="/facts/Risk_assessment/vlG9Uf0h">risk assessment</a> to set approval standards below this level.
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<p>The <a href="/facts/United_States_Environmental_Protection_Agency/ghI985SI">United States Environmental Protection Agency</a> 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).
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Lowest-observed-adverse-effect level