Algae (Raphidocelis) reduce combined toxicity of nano-TiO₂ and lead on C. dubia

Nanoparticles (NPs) often serve as carriers of background toxins and enhance their toxicity on aquatic organisms such as Ceriodaphnia dubia (C. dubia). However, foods, especially algae, are also present in natural water and impacts this type of toxicity. This study investigated the effect of algae on the combined toxicity of nano-TiO₂ and lead (Pb). A mixture of yeast-trout chow-cereal leaves (YTC) was also used as another model food. Results indicated that, both algae and YTC significantly reduce the combined toxicity of nano-TiO₂ and Pb. Further investigation indicated that the ingestion of algae had minimal impacts on Pb uptake by, Pb depuration from, and Pb distribution within the C. dubia. Therefore, the toxicity reduction from algae ingestion should come from mechanisms other than the change in Pb mass and speciation in C. dubia, which will need future investigation. Nevertheless, the effect of food on the mitigation of combined toxicity of NPs and heavy metals must be considered when assessing the toxicity of nanoparticles in the natural environment because food always exists in natural waterbodies where aquatic organisms grow.