Toxicity of lead on Ceriodaphnia dubia in the presence of nano-CeO2 and nano-TiO2

► Pb is significantly accumulated on the surface of CeO2 and TiO2 nanoparticles (NPs). ► NPs are significantly ingested in the gastrointestinal tract of Ceriodaphnia dubia. ► The ingestion of Pb-loaded NPs enhances the overall toxicity of Pb. ► Reducing pH enhances the overall toxicity of Pb, with or without NPs.