Effect of natural organic matter on the photo‐induced toxicity of titanium dioxide nanoparticles

Nano-TiO2 is the most widely used form of nanoparticles in commercial industry, and come in two main configurations: rutile and anatase. Rutile TiO2 is used in UV screening applications, while anatase TiO2 crystals have a surface defect that makes them photoreactive. There are numerous reports in the literature of photo-induced toxicity to aquatic organisms following co-exposure to anatase nano-TiO2 and UV. All natural freshwater contains varying amounts of natural organic matter (NOM), which can drive UV attenuation and quench ROS in aquatic ecosystems. The goal of this research was to examine how NOM alters the photo-induced toxicity of anatase nano-TiO2. D. magna neonates were co-exposed to NOM and photoexcited anatase nano-TiO2 for 48 hours. NOM concentrations as low as 4 mg/L reduced anatase nano-TiO2 toxicity by nearly 100%. These concentrations of NOM attenuated UV by less than 10% in the exposure system. However, ROS production measured using a fluorescence assay was significantly reduced in a NOM concentration dependent manner. Taken together, these data suggest that NOM reduces anatase nano-TiO2 toxicity via an ROS quenching mechanism and not by attenuation of UV. This article is protected by copyright. All rights reserved