Nanosized titanium dioxide UV filter increases mixture toxicity when combined with parabens.

To address the concern about the environmental impact of engineered nanoparticles frequently used in the recently marketed personal care and hygiene products (PCPs), we conducted a toxicity assessment and determined the EC50 values of the nanosized inorganic UV filter TiO2 (nano-TiO2), as well as those of the organic UV filter oxybenzone (BP3) and three parabens (methyl, propyl, and benzylparaben) present in most PCPs formulation. The bioassays were carried out through standardized toxicity bioassays on two environmentally relevant aquatic species i.e. Daphnia magna and Phaeodactylum tricornutum. For nano-TiO2 48 h EC50 on D. magna was 3.09 mgL-1 and for parabens ranged from 32.52 to 1.35 mgL-1. The two most toxic compounds on D. magna, nano-TiO2 and benzylparaben (BzP), were further tested with the algae. For nano-TiO2 72 h EC50 value was 2.27 mgL-1 and for BzP it was 10.61 mgL-1. In addition, D. magna was exposed to selected binary mixtures of the target compounds i.e. nano-TiO2+BP3, nano-TiO2+BzP and BP3+BzP On the endpoint of 48 h, a synergistic action was observed for nano-TiO2+BP3 and nano-TiO2+BzP, but an antagonistic effect occurred in the mixture BP3+BzP. These findings suggest that nano-TiO2 can increase the toxicity of the mixture when combined with other compounds.