Based on the information provided in this Report, one can conclude that lung overload in its distinct form with all its consequences is a rat specific phenomenon. Rat inhalation studies with PSPs in which lung overload has been observed have therefore no human relevance with regard to any observed tumourigenic effects and, without appropriately considering the dose-response differences between rat and humans, of little human relevance for non-tumourigenic effects.
From a worker and consumer protection point of view, it is not considered to be meaningful or helpful if, as a general principle, all poorly soluble particles of low toxicity would be classified as STOT-RE and/or inhalation carcinogens on the basis of data that are not relevant to humans. Such situation would undermine the objective of chemical hazard classification schemes. The mechanisms of toxicity of inhaled PSPs are well understood, allowing the establishment of safe exposure levels and identification and use of adequate risk management measures. This knowledge already results in practical application for setting of occupational exposure limits and, under the EU REACH Regulation, the setting of derived no effect levels (‘DNELs’). For hazard classification purposes, it is recommended to clarify the UN GHS/EU CLP guideline values for STOT classifications as human equivalent concentrations (HECs).