Towards a Definition of Harmless Nanoparticles from an Environmental and Safety Perspective

Figure 5

TEM image of sludge without (a) or with (b) the addition of 50 mg/L Fe₂O₃ NPs after 6 h. (a) Inset panels (A)–(C) and (D)–(F) show three kinds of bacteria in the sludge. In panel (c), the reaction was allowed to continue for 36 hours in the presence of Fe₂O₃ NP. The insets (G)–(I) show bacteria at the 36 h time point. Arrows indicate Fe₂O₃ NPs.