Measures of pollutant concentration

NOEL or NOEC (No Observed Effect Level or Concentration) is a toxicological endpoint in the toxicity determination.

The NOEL is 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 means the dose at which no adverse effect is observed.

The NOEL for a substance always relates to a particular biological measurement method with a specific application form and a specific species or a specific cell culture system can be used in various processes a substance thus have different NOELs. Many published NOEL values ​​are based on subchronic toxicity studies with oral administration in rodents.

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

While the NOAEL determination, a limited number of evaluations is sufficient to determine damage, evidence of the absence of any effect is problematic because limited by the number of practicable investigations.

Furthermore - as well as for NOAEL - to consider that the NOEL is only a single value in a given dose range. The precise dose at which no effect is observed would actually, so only approximately identified.

NOEC is not always determined, for example, when at each test concentration, a significant effect occurs. Also may be intended for the NOEC no confidence.

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