The first comprehensive safety study of Magnéli phase titanium suboxides reveals no acute environmental hazard

Abstract

Magnéli phase titanium suboxides (Magnéli TiO_x) are novel conductive materials with great industrial potential. This is the first comprehensive investigation to provide an extensive dataset for hazard characterisation of Magnéli TiO_x using six standardised test organisms and two human cell lines. Three Magnéli TiO_x particles and three anatase crystalline phase TiO₂ nanomaterials with different primary powder sizes, but similar hydrodynamic diameters in biological media, were investigated. All Magnéli TiO_x and TiO₂ nanomaterials induced negligible biological responses in Tetrahymena thermophila, Lemna minor, Artemia franciscana and Danio rerio. Adverse effects were found only at 100 mg L⁻¹ where approximately 50% endpoint inhibition was recorded in the cases of Daphnia magna exposed to two Magnéli TiO_x, Pseudokirchneriella subcapitata exposed to all three Magnéli TiO_x and HepG2 cells exposed to one type of Magnéli TiO_x. This study provides the first evidence that the tested Magnéli TiO_x are not acutely hazardous according to existing EU classification for conventional chemicals.