Approaches for establishing human health no effect levels for engineered nanomaterials

Current Technical Guidance Documents for preparing risk assessments, like the guidance for the implementation of REACH, have limited focus on chemical substances in the particulate form and generally do not focus on substances in the nanoform. Within the ENRHES project a comprehensive and critical scientific review of publicly available health and safety information on four types of nanoparticles was performed. Based on the identified exposure and hazard data, basic human health risk assessment appraisals were carried out for fullerenes, carbon nanotubes, nano-silver and nano-titanium dioxide. These risk assessment appraisals followed the structure of a regulatory risk assessment and if possible and relevant, it was attempted to derive indicative human no-effect levels from key studies by applying assessment factors as suggested in the technical guidance document for REACH. These assessment factors address differences and uncertainty related to exposure features between test animals and humans (time, respiratory volume), other interspecies and intraspecies differences and factors for extrapolation to chronic duration. If required, the severity of effects and the quality of the database can be addressed by additional factors. Recently other procedures for deriving human no-effect levels have been published and these are compared to the ENRHES basic risk assessment appraisals. The main differences were observed in relation to evaluating the differences in animal and human exposure situations and interspecies differences, and in applying assessment factors for intraspecies differences for local effects. The applicability of the REACH guidance for nanomaterials is currently being investigated for possible adaptations, considering the specific behaviour and mode of action of