Long-term effects of nanoscaled titanium dioxide on the cladoceran Daphnia magna over six generations.

We investigated the impact of nanoscaled titanium dioxide (nTiO2) on Daphnia magna populations in a multi-generational study over six generations (F0-F5). Each generation was exposed for 21 days to nTiO2 (AEROXIDE(®) TiO2 P25, primary particle size 21 nm) while mortality, individual growth, reproduction and population growth rates (PGR) were assessed as endpoints. The size distribution of nTiO2 in the single test media was analysed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). nTiO2 concentrations were measured using ICP-MS. Mortality and individual growth of D. magna were significantly affected with increasing exposure duration and concentration. Daphnids demonstrated decreasing reproduction over generations in all treatment groups (1.19-6 mg/L) but not in the control. At concentration levels of 1.78 mg/L chronic exposure resulted in a population collapse after five generations. This study indicates that multi-generational studies are suitable for evaluating long-term effects of nanoparticles since they reflect potential effects more accurately than single generation tests.