Ecotoxicological effects of titanium dioxide nanoparticles and Galaxolide, separately and as binary mixtures, in...

Nano-TiO₂ and Galaxolide (HHCB) are continually released into the environment because they are common ingredients of personal care products. In this study, the effects of nano-TiO₂ and HHCB, individually and as binary mixtures, on Raphanus sativus were investigated. Growth indices (germination rate, root length, and shoot elongation), random amplification of polymorphic DNA profiles of DNA damage in the seedling roots, and expression of genes related to DNA damage, repair, and the cell cycle were assessed. Radish germination was not affected by nano-TiO₂ (5-200 mg L^-1) but was inhibited by HHCB (≥50 mg L^-1). Nano-TiO₂ and HHCB both caused severe DNA damage, including DNA mismatch damage, DNA double-strand breaks, and chromosomal damage. The binary mixtures indicated antagonistic effects occurred, and 200 mg L^-1 nano-TiO₂ decreased the genetic toxicity of HHCB. Of the genes that were examined, MRE11 and WRKY40 were the most sensitive to nano-TiO₂ and HHCB, indicating that these genes could be used as sensitive biomarkers for exposure of R. sativus to nano-TiO₂ and HHCB. The results improve our understanding of the risks posed by nano-TiO₂ and HHCB to R. sativus in particular and possibly to other plants.