The physical, chemical and biological properties of various nanomaterials differ substantially – as do the potential risks they pose. We argue that nanomaterials must be categorized based on the location of the nanoscale structure in the system/material before their hazards can be assessed and propose a categorization framework that enables scientists and regulators to identify the categories of nanomaterials systematically. The framework is applied to a suggested hazard identification approach aimed at identifying causality between inherent physical and chemical properties and observed adverse effects reported in the literature. We tested the workability of the proposed procedure using nanoparticles as an illustrative case study. A database was generated noting the reported inherent physical and chemical properties of the nanoparticles tested and the main effects observed. 428 studies were noted in the database reporting on a total of 965 nanoparticles. We found that although a limited number of studies have been reported on ecotoxicity, more than 120 and 270 have been reported on mammalian toxicity and cytotoxicity, respectively. In general there was a lack of characterization of the nanoparticles studied and it was not possible to link specific properties of nanoparticles to the observed effects. Our study shows that future research strategies must have a strong focus on characterization of the nanoparticles tested.

It remains unclear which kinds of nanoproducts are available on the European market, although this information is a prerequisite for any kind of exposure and risk assessment. In order to address this lack of information, we have established The Nanodatabase (http://www.nanodb.dk), which is an online inventory of products claimed by manufacturers to contain nanomaterials (NMs) or be based on nanotechnology. The database currently entails 2231 products. The database is unique and includes basic information about the product (name, NM used, location of NM, product category, etc.) as well as a safety evaluation of each individual product according to the NanoRiskCat-framework. Our analysis of products that are currently present in the database shows that most products fall into “personal care” and “clothing” categories (≥300), followed by “sporting goods” and “cleaning” (>200). Silver and titanium dioxide are the most used NMs, but it is not possible to identify the NMs used for almost 60% of the products in the database. The data analysis shows that for most product categories the dominant route of exposure is dermal, and that the exposure potential as well as human and environmental hazard potential of most products is either “high” or “unknown”. In order to address the current lack of reporting by manufacturers when it comes to nanoproducts, we recommend that it is made mandatory to disclose and report any nanomaterials used in a consumer product and it becomes illegal to advertise and market products as “nano” when they have no content of nanomaterials.