No observed adverse effects concentration NOAEC

Because of the first of these uncertainties (the extrapolation across species), assessments of risks to human health apply an uncertainty or safety factor of 100 to the experimentally derived no observed adverse effect concentration (NOAEC), in other words the NOAEC is divided by 100 to derive a no-effect level for human toxicity. This factor has been used since 1961, when it was chosen on an essentially arbitrary basis (RCEP, 2003, p22). In the assessment of risks to the environment, application factors of 10, 50, 100 or 1000 are applied to the results of tests carried out on specific species,2 depending on the species used and whether the tests were long term or short term. Evidence to the Royal Commission on Environmental Pollution (RCEP) for their report Chemicals in products indicated that these are merely extrapolation factors — they express the statistical variability of test results but do not effectively take into account inter-species variability, the vulnerability of threatened species, lifetime exposures or the complexity of biological systems... 

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