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90635 
Journal Article 
Abstract 
Aquatic fate and toxicity of nanoparticles: Agglomeration, sedimentation and effects of daphnia magna [Abstract no 1384] 
Wiench, K; Landsiedel, R; Zok, S; Hisgen, V; Radke, K; Van Ravenzwaay, B 
2007 
1 
Toxicologist
ISSN: 0731-9193 
96 
1 
286 
The nanoparticular inorganic pigments titanium dioxide (TiO2) and zinc oxide (ZnO) are used in sunscreens to protect the human skin against UVB light. It has been demonstrated that these nanoparticles do not penetrate human skin. However, the possible impact on the environment and its aquatic organisms has not been well examined.
We analysed the agglomeration and sedimentation and tested the acute aquatic toxicity of TiO2 and ZnO particles. The influence of the test medium, the dispersion method and the pH on the fate and the effects of the particles were tested. Additionally, the characteristics of the nano-scaled materials were compared to those of the micron-scaled materials.
The particle size distributions in the test dispersions were characterized by laser scatterring and dynamic light scattering analysis, and sedimentation of particles was visually observed at different time points. The mass of non-sedimented particles was determined. Acute aquatic toxicity to Daphnia magna was tested considering the OECD Test Guideline 202.
Dispersion of the nano-powders generally leads to suspensions with agglomerated particles and sedimentation. However, agglomeration and sedimentation varied significantly depending on the choice of test media.
The acute aquatic effect of nano-TiO2 was low and did not significantly differ from that of the micron-sized material.
The aquatic toxicity of ZnO particles largely depended on the solubilisation of Zn rather than on the particles themselves. Therefore the pH of the test medium is critical. Microscopy of the Daphnides revealed articles in the intestine, the filtering chamber and inside the carpax as well as adsorption to the body surface. Adsorbed and ingested particles were agglomerates rather than primary nano-scaled particles. 
Society of Toxicology 46th Annual Meeting and ToxExpo 
Charlotte, NC 
March 25-29, 2007