In an article on February 24, 2021, the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) announced the publication of a technical report reviewing available scientific information used to determine a chemical’s derived no-effect levels (DNELs).
DNELs are generally defined as “the exposure level beneath which a substance does not harm human health” and establishing a DNEL represents a vital step in the assessment of chemicals under REACH. The European Chemicals Agency (ECHA) defines DNELs based on “recognized international practices” as well as, extrapolating from animal studies to human exposure by applying assessment factors (AFs).
The purpose of applying AFs is to address uncertainties as well as variability, for example, among humans, sensitive subpopulations, and when extrapolating across species. Ideally, AFs should be based on experimental data, however, data scarcity often results in the application of so-called “default AFs”.
However, according to ECETOC, the default approach is “in some cases overly conservative” and the authors explain that the results of their review support the occasional use of alternative factors. According to the authors, the application of this concept requires chemical-specific reasoning, as well as transparent documentation. The organization writes that the higher costs required to attain such chemical-specific assessment factors may limit this approach to only a small number of high-profile or high-value chemicals. In the presented review, the organization also concluded that the available scientific landscape regarding intra- and inter-species variation has not changed much in the last ten years, confirming opinions of their earlier reviews. Nevertheless, ECETOC recommends reviewing AFs to consider differences in study duration and to avoid the development of divergent practices.
ECETOC (February 24, 2021). “Tr – 136 Assessment Factors To Derive Dnels – Critical Evaluation Of The Status Quo.”