The<unk> <unk> , or the<unk><unk> -adverse-effect concentration <unk> , is the<unk>  concentration or amount of a substance found by experiment or observation that causes an adverse alteration of morphology, function, capacity, growth,<unk> opment, or lifespan of a target organism distinguished from normal organisms of the same species under defined conditions of exposure. Federal agencies use set approval standards below this<unk> . The United States Environmental Protection Agency defines<unk>  as the<unk><unk>  of a chemical stressor evaluated in a toxicity test that shows harmful effects on a plant or animal. While<unk> s and<unk> s are similar, they are not interchangeable. A<unk>  refers to a dose of chemical that is ingested, while a<unk>  refers to direct exposure to a chemical (e.g., through gills or the skin).
Lowest-observed-adverse-effect level
No-observed-adverse-effect level
Relative biological effectiveness
Appropriate use criteria
Unwarranted variation
Risk–benefit ratio
Weekend effect
Biological plausibility