Incineration of nano-materials: physical and chemical transformations and biological consequences of emissions

According to the 2016 OECD report 'Nano-materials in waste streams', 30 % of waste is incinerated. This process can strongly affect the physical and chemical properties of any nanoparticles in the waste matter, possibly modifying their initial toxicity. Little is known about the spread of nanoparticles in the resulting by-products (smoke and residues from the incineration of the nano-materials). In the Nano Tox'in project, nano-materials were incinerated in a laboratory with a two-fold aim: to study their physical and chemical properties and their by-products in detail, and to assess the impact on the in vitro toxicity of the transformation of the nano-materials' initial nanoparticles into released particulate matter (PM) in aerosols and in the residues (ash). We showed that the nanoparticles were mainly concentrated in the ash. Our results also confirmed that the toxicological profile of the PM is directly related to the toxicity of the polymer matrix host, while that of the ash seems directly linked to the intrinsic toxicity of the nanoparticles. The size, chemistry, and rate of nano-particles along with the nature of the matrix therefore affect the in vitro toxicity. The new project, NanoDetox, will enable us to study the impact of mixed waste (representing the waste streams) and assess the physical and chemical transformations and the effects of synergies and antagonisms of nanoparticles on the in vitro toxicity of soot and/or ash. (authors)