Acute toxicity of cerium oxide, titanium oxide and iron oxide nanoparticles using standardized tests

In this study, several standard toxicity tests have been performed on selected inorganic nanoparticles. Acute toxicity tests were selected according to their extensive use in toxicological studies and included phytotoxicity using several seeds. Daphnia magna and a bioluminescent test (Microtox (R)). All of them have been used in several international regulations as toxicity assays. In the case of nanoparticles (NPs), we have studied those of cerium oxide, titanium dioxide and iron oxide. Iron oxide NPs are well known and broadly used and were selected because of their low toxicity. Titanium dioxide and cerium oxide NPs are currently being used in several fields such as photocatalysis and medical applications, but their toxicity effects have been scarcely studied. Our results revealed that cerium NPs are extremely toxic in the entire set of tests conducted (inhibition higher than 80% at very low concentrations for the bioluminescence test and LC50=0.012 mg/ml of mortality in the assays of D. magna), whereas titanium NPs were practically inert in terms of toxicity (values similar to those of controls). The possible toxicological effect of the solvents necessary to stabilize NPs in liquid medium for the three cases (stabilizers) has been also studied. Only in the germination test (phytotoxicity) of some seeds they showed some detrimental effect to germination. In general, the standardized tests proposed in this study have proved to be very useful in the determination of NPs toxicity when no or few data are available, although further work is necessary in the case of the germination test. (C) 2010 Elsevier B.V. All rights reserved.