TR 110 – Guidance on Assessment Factors to Derive a DNEL

from November 2010

ECETOC publishes its ‘Guidance on Assessment Factors to Derive a DNEL’

The chemical industry has reached an important milestone this month by having submitted their dossiers for the first REACH registration deadline. This was also a significant timeline for ECETOC to observe as the report on “Guidance on Assessment Factors to Derive a DNEL’ had to be published by then. Companies were already referring to the tables on assessment factors communicated with the draft report this March, i.e. in preparation for the Workshop in Ispra/Italy where we discussed the underlying principles with regulators, academia and experts from industry. Since then, the ECETOC Task Force has worked diligently to address the helpful comments made at the Workshop. This required, for example, evaluating many original data from toxicological studies on industrial chemicals reported in the open literature. The guidance has now been published as Technical Report No. 110 (available at

TR 110 addresses the (human health) assessment factors for setting a DNEL. In the REACH Technical Guidance Document, chapter R.8 “Characterisation of dose[concentration]-response for human health’ proposes a tiered and systematic approach for the delineation of DNEL (and DMEL). This approach is supported by ECETOC in principle, but it appeared advisable to provide additional scientific arguments and recommendations for the derivation of DNEL (to note: DMEL were not addressed). The Task Force that had started its work in mid-2009 critically assessed the approaches laid out in the REACH TGD, re-visited the previously published guidance on assessment factors (TR 86) and supplemented this with an updated review of the literature published on this topic during the intervening years. Although for most chemicals a DNEL will solely be based upon animal data, for some health effects data derived in humans will be an additional and important source of information. Hence, the conclusions from TR 104, providing a guide for an integrative framework for human and animal data, have also been referred to in TR 110.

ECETOC, in line with the R.8 guidance, recognise that the use of “informed’ assessment factors is preferred over “default’ assessment factors wherever possible, whether supported by substance-specific data or, for example, by read-across to other chemicals or mechanisms of action. The use of informed assessment factors for hazard and risk assessment is well-established and has been used for many years by organisations such as the Scientific Committee on Occupational Exposure Limits (SCOEL) and national competent authorities to set occupational exposure limits. The guidance in TR 110 is illustrated by a number of case studies drawn from, for example, SCOEL documentation, for which the outcome of assessments based on default (REACH TGD, chapter R.8) versus ECETOC recommended assessment factors has been compared.

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