To the Editor

We agree with your Editorial 'Join the dialogue' (Nature Nanotech. 7, 545; 2012) that there is a need for guidelines on materials characterization requirements when reporting nanotoxicology research. However, defining a minimum set of requirements will not substitute for a rigorous peer-review process because materials characterization per se does not necessarily mean that measurements have been performed using state-of-the-art methods, or that the parameters are directly associated with the observed biological effects. Different types of information (and consequently, the use of different methods) are needed depending on the purpose of the study. Materials characterization in the relevant biological matrix is sorely needed and developing methods to do this is important. The use of reference materials can facilitate comparisons between nanotoxicological studies, and such materials should be widely available to the community, for example, through a central repository.

In addition to pinpointing hazard mechanisms and/or ranking nanomaterials as a function of their hazard using in vitro and/or in vivo models, we think it is necessary to broaden the discussion to consider the types of information needed to enhance the quality and comparability of exposure-assessment studies (Brouwer, D. et al. Ann. Occup. Hyg. 56, 1–9; 2012). Nanomaterial risk is a function of hazard and exposure, and at the heart of both disciplines is the need to understand the properties of the nanomaterials in question. We fully agree with Schrurs and Lison (Nature Nanotech. 7, 546–548; 2012) that more coherence is needed in the way that nanotoxicological studies are performed, but this also applies to nanosafety research in a broader sense. One of the main objectives of the European NanoSafety Cluster (www.nanosafetycluster.eu) is to improve coherence in the area of nanosafety research and to harmonize studies in this field. Furthermore, the Cluster aims to avoid duplicating work, and to provide a forum for discussion and bottom-up planning of research activities in the European Union. To this end, the Cluster (of the Sixth Framework Programme (FP6) and FP7 projects along with key national projects) is organized into several working groups focusing on: materials, hazard, exposure, risk, (mathematical) modelling, databases and dissemination. The Cluster is currently putting together a “chart of state-of-the-art methodologies in nanosafety research”, and the issue of whether a set of minimal requirements for materials characterization can be defined has been taken on board.