NOEL

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NOEL or NOEC ( N o O bserved E ffect L evel or C oncentration) is a toxicological endpoint in the toxicity determination .

The NOEL corresponds to the highest dose or exposure concentration of a substance in subchronic or chronic studies in which no statistically significant treatment-related effect can be observed. In contrast, the NOAEL describes the dose at which no harmful effect is observed.

The NOEL for a substance always relates to a specific biological measurement method with a specific form of application and a specific animal species or a specific cell culture system, so a substance can have different NOEL values ​​in different processes. Many published NOEL values ​​relate to subchronic toxicity studies with oral administration in rodents.

The determination of the NOEL is problematic in various respects, which is why there are efforts to abolish the NOEL as an international standard.

While a limited number of evaluations is sufficient to determine damage in the NOAEL determination, the detection of the absence of any effect is problematic because it is limited by the number of tests that can be carried out in practice.

Furthermore, as for the NOAEL, it must be taken into account that the NOEL represents only a single value in a given dose series. The exact dose at which no effect could actually be observed is therefore only approximately identified.

The NOEC cannot always be determined, for example if a significant effect occurs at each test concentration. Also, no confidence interval can be determined for the NOEC .

See also

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  1. ↑ OECD : Current approaches in the statistical analysis of ecotoxicity data: A guidance to application , 2006.
  2. ^ Mark Crane, Michael C. Newman: What level of effect is a no observed effect? In: Environmental Toxicology and Chemistry . 19 (2), 2000, pp. 516-519, DOI: 10.1002 / etc. 5620190234 ( PDF ).
  3. ↑ Peter F. Chapman, Mark Crane, John Wiles, Frank Noppert, Eddie McIndoe: Improving the quality of statistics in regulatory ecotoxicity tests. In: Ecotoxicology . 5 (3), 1996, pp. 169-186, DOI: 10.1007 / BF00116338 .