Trophic transfer of TiO₂ nanoparticles from daphnia to zebrafish in a simplified freshwater food chain

The rapid development of nanotechnology and the corresponding increase in the use of manufactured nanomaterials (MNMs) in commercial products have led to concerns about the health risks and environmental impacts of such nanosized materials. One of the most significant and currently not well-understood risks is their potential transfer and magnification in food webs. To address this concern, a simplified model of a freshwater food chain including a low trophic level organism (daphnia, Daphnia magna) and a high trophic level organism (zebrafish, Danio rerio) was established. Our results provide the first direct evidence that nanoscale TiO₂ particles (nTiO₂) can transfer from D. magna to D. rerio by dietary exposure. However, no biomagnifications of nTiO₂ was observed in this simplified food chain because the values of the biomagnification factors (BMF) in this study (0.024 and 0.009) were all less than one. Compared to the dietary intake, D. rerio could accumulate nTiO₂ by aqueous exposure with high bioaccumulation factors (BCFs) of 25.38 and 181.38 for 0.1 and 1.0 mg L^-1 exposure groups, respectively. Nevertheless, higher body burden of nTiO₂ in the dietary exposure groups than that in the aqueous exposure groups demonstrated that dietary intake may constitute a major route of potential nanomaterial exposure for a higher trophic level of aquatic organisms. This study represents the first examination of the potential food chain transfer and biomagnification of nTiO₂ in an aquatic ecosystem.