For some time now, engineered and surface-modified nanomaterials have been used in various everyday products. For the material flow analyses presented in the following paper, six nano-based consumer products were selected that are available on the Austrian market and primarily contain metallic nanomaterials (nano-SiO2, -TiO2, -Ag or CdSe quantum dots); one sample product contained carbon nanotubes (CNTs).
For the purpose of the material flow analyses, it was necessary to estimate the amounts of nanomaterial input at the product level. On the basis of available product information and academic publications, initial estimates of consumption in Austria were prepared. In the case of the sample product “televisions with quantum dot displays,” there was too little data available to do so. However, this scenario offers valuable proof of the fact that little to no product information is available for many product categories, making it impossible to quantitatively estimate the amount of nanomaterials in waste streams.
The initial estimates show that tons of nano-TiO2 are already used in sun creams (ca. 5.4 to 40.8 t/year in Austria). In contrast, only several kilograms each of nano-SiO2 (in automotive paint sealants), nano-Ag (in indoor paints and washcloths), and CNTs (in tennis rackets) are used each year.
Based on the material flow analyses it can be assumed that, in the course of waste treatment, metallic/metal oxide nanomaterials very likely enrich in secondary waste like combustion residues, which in turn predominantly end up in landfills. Carbon-based nanomaterials like CNTs are most likely completely oxidized in the course of incineration. However, their elimination can only be ensured if they are subjected to high temperatures for a sufficiently long time. The uncertainties/substantial variances in the projected nanomaterial flows clearly show that there are still considerable gaps in our knowledge and available information, and that research regarding the exact environmental fate of nano-products especially into their behavior and potential emission pathways in the disposal phase is urgently needed.