Toxicity of lanthanum oxide (La2O3) nanoparticles in aquatic environments†
This study demonstrates the acute toxicity of lanthanum oxide nanoparticles (La2O3 NP) on two sentinel aquatic species, fresh-water microalgae Chlorella sp. and the crustacean Daphnia magna. The morphology, size and charge of the nanoparticles were systematically studied. The algal growth inhibition assay confirmed absence of toxic effects of La2O3 NP on Chlorella sp., even at higher concentration (1000 mg L−1) after 72 h exposure. Similarly, no significant toxic effects were observed on D. magna at concentrations of 250 mg L−1 or less, and considerable toxic effects were noted in higher concentrations (effective concentration [EC50] 500 mg L−1; lethal dose [LD50] 1000 mg L−1). In addition, attachment of La2O3 NP on aquatic species was demonstrated using microscopy analysis. This study proved to be beneficial in understanding acute toxicity in order to provide environmental protection as part of risk assessment strategies.