## 2 Exposure
### Release of NMs (from the Product) into the Environment  
Some early studies evaluated the release of NMs into the wider environment from some selected nanomaterial-containing products during the consumption phase [28,29]. One study used life-cycle based modelling and embraced the whole life-cycle of products that contain certain NMs [30]. This study provided the first comprehensive assessment of the potential concentrations and the associated environmental risks of nano-TiO\({}_{2}\), nano-Ag and carbon nanotubes (CNTs). These studies estimated concentration levels of selected NMs in different systems (aquatic, terrestrial, waste-water systems) based on the available knowledge of the total usage of products containing NMs.  
While the release of NMs is obviously a precondition of downstream exposure, little has been done so far to examine such release in a rigorous and systematic manner. General processes and areas of possible release of nanoscale entities and NMs are: the production process; the handling, packaging, use and misuse of such materials; the ageing processes of NMs; and end-of-life activities such as recycling and disposal [14].  
Possible release during production may occur through leaks to water and air in closed systems or open production processes. These have been studied in several European and national studies such as NANOSH, CarboSafe and NanoGEM [31]. The areas of \"handling and use\" and \"ageing\" are vast and complex. The former includes the handling of powders, diffuse emission from production plants, mechanical treatment of NMs such as sanding and drilling, abrasion during use, spraying of 'nano'-sprays. The latter covers all processes taking place in the environment such as selective wear and tear, degradation, wash-out, and the increased brittleness of some materials.  
End-of-life activities include: (1) re-use or recycling, such as disassembling, and mechanical or thermal processes like crushing, melting and torch cutting; (2) waste treatment, such as incineration; and (3) disposal, such as landfill. The release of nanoscale entities can never be excluded as a possibility, especially during high energy processes.  
**Recommendation 2**: There is a general lack of knowledge on the release of NMs. More research and development activities need to be aimed at understanding the release of NMs from processes and products during use. This applies both to standard non-nanotechnology processes and to new nanotechnology-related processes. Specifically we need: (a) detailed studies of processes including the nanoscale; (b) standardised testing for certain possibly relevant mechanisms and routes of release; (c) the derivation of quantitative information on the possible release rates; and (d) characterisation of the physical, chemical and bio-interface properties of NMs that are dependent on specific release conditions (e.g., abrasion) that is useful for safety measures.  
**Recommendation 3**: Concerning release, for safety purposes we need data on the leach rate and/or decay rate of nanoscale entities in realistic landfill conditions. We already know that free NMs can penetrate clay (typically used as a liner in landfill) and move into ground water, so the expectation is that there will be some long-term slow release at the end of a product's life. Of course, at this early stage, if product manufacturers can design for re-use then the amount going to landfill may be reduced.