REACH DNEL establishment for PSP

There is substantial evidence that poorly soluble particles of low toxicity, whether nano- or microsized, exert toxicologically relevant adverse effects via a threshold mode of action. Hence, the derivation of DNELs based on NOAELs/NOAECs as derived in animal inhalation studies, adjusted for human equivalent concentrations by appropriate dosimetry modelling, is toxicologically justified. Due to the higher sensitivity of the rat compared to humans with regard to lung overload driven effects, an overall assessment factor of 1 for intra- as well as interspecies differences is considered suitable and sufficient. While within the scope of this work it was not possible to scientifically justify a default assessment factor for exposure duration extrapolation, the Task Force recommends further investigations on the need of such AF and reconsideration as new knowledge becomes available.