OECD GUIDELINE FOR THE TESTING OF CHEMICALS DISPERSION STABILITY OF NANOMATERIALS IN SIMULATED ENVIRONMENTAL MEDIA

1. The increased production and wide usage of manufactured nanomaterials suggest a higher probability of finding them in natural systems, where transport and distribution in the environment will take place especially via aqueous media. This has raised the question and lead to discussion as to whether the existing regulatory testing protocols are sufficient and adequate to assess the fate of manufactured nanomaterials and their impact on the natural system(s) of interest. Dispersion stability of the nanomaterials was identified as important parameter affecting the environmental behaviour of nanomaterials. This parameter depends on the physicochemical characteristics of the nanomaterial itself, the physicochemical characteristics of the suspension medium, suspension preparation, concentration of the nanomaterial and concentration of other substances and particles in the suspension. The dispersion stability is also highly dynamic in many cases, because it is controlled by kinetics (energy barriers) rather than thermodynamic equilibrium. Therefore information on nanomaterials dispersion stability and agglomeration behaviour is, beside e.g. dissolution rate, one prerequisite for a robust and reliable further testing of nanomaterials.