Table 2.

A set of key issues relevant for SbD approach.

Issue	Description	Need
Identification/characterisation of NM-based biocidal agent	Knowledge on the key characteristics that influence the release, exposure, behaviour, effects and subsequent environmental and human risks of NMs.	Reasonably priced, accessible, standardized and validated methods and procedures to characterize NM in different media according to the EC definition.
Transformation of NM-based biocidal agent	Knowledge on the circumstances, extent and rate of dissolution; change of the structure of NM throughout the different stages of their life cycle.	Life Cycle Assessment in different biological and environmental matrices; standardized and validated methods to test or predict the extent and rates of the transformation of NMs.
Dose metrics	Dose that determines a particular response in a test system; production volume of the substance; dose levels at which toxicity effects are observed in experimental tests and which can be compared to the estimated exposure levels to estimate the risk.	Development and use of standardized protocols for sample preparation and characterization of NM within exposure and toxicity studies; identification of the most appropriate metrics for each type of NM within each specific route of exposure and toxicological endpoint.
Extrapolation	Information (on physico-chemical characteristics, exposure and/or hazard) of different forms, types and sizes of NMs (or the bulk material) for extrapolation, read across or grouping within the risk assessment of NMs.	Development of nano-specific approaches for extrapolation, interpolation, read across and grouping based on the key characteristics/properties that influence the release, exposure, behaviour (fate and kinetics), effects (hazards) and subsequent risks of NMs.
Fate and kinetics	Interaction of NMs with their environment that change their physico-chemical characteristics, including their surface composition, ability to aggregate, agglomerate and/or dissolve.	Knowledge on the key characteristics that influence the fate, behaviour and kinetics of NM with respect to the life cycle assessment of nanoproducts (including the release of NMs from products).