Nano-TiO2 phototoxicity in fresh and seawater: Daphnia magna and Artemia sp. as proxies

Abstract

Nowadays, the industry is quite commonly using nanoparticles of titanium dioxide (nTiO2)especially in sunscreens, due to its higher reflective index in comparison to micron size TiO2. It shigh demand causes its widespread environmental occurrence, thus damaging the environment.The aquatic ecosystems are the most vulnerable to contamination by nTiO2. Like other engineered nanoparticles, nTiO2has demonstrated generation of reactive oxygen species (ROS) and reactive halogen species (RHS) in the aquatic environment under UV radiation. This study investigated the toxicity of nTiO2towards two aquatic indicator organisms, one from freshwater (Daphnia magna) andthe other from seawater (Artemiasp.), under simulated solar radiation (SSR).Daphnia magna and Artemiasp. were co-exposed in 16 h SSR and 8 h darkness cycles to different concentrations of nTiO2.The estimated EC50 at 48 h forD. magna was 3.16 mg nTiO2/L, whereas for A. sp. no toxic effectswere observed. When we exposed these two organisms simultaneously to 48 h of prolonged SSRusing higher nTiO2 concentrations, EC50 values of 7.60 mg/L and 5.59 mg/L nTiO2forD. magna and A. sp., respectively, were obtained. A complementary bioassay was carried out withA. sp., byexposing this organism to a mixture of nTiO2and organic UV filters (benzophenone 3 (oxybenzone,BP3), octocrylene (OC), and ethyl 4-aminobenzoate (EtPABA)), and then exposed to SSR. The results suggested that nTiO2could potentially have negative impacts on these organisms, also this workoutlines the different characteristics and interactions that may contribute to the mechanisms of environmental (in salted and freshwater) phototoxicity of nTiO2and UV radiation, besides their interaction with organic compounds.