UV-dependent freshwater effect factor of nanoscale titanium dioxide for future life cycle assessment application

Environmental impacts of nanoscale titanium dioxide (TiO₂ ) should be assessed throughout the lifetime of nanoparticles (NPs) to improve the state of knowledge of the overall sustainability. Life cycle assessment (LCA) has been previously recognized as a promising approach to systematically evaluating environmental impacts of NPs. As a result of their unique nanospecific properties, characterization factors (CF) were previously used for compensating the release and potential impacts of TiO₂ NPs. However, because TiO₂ NPs are known to generate reactive oxygen species and elicit toxicity to freshwater organisms, the lack of adequate UV-dependent effect factors (EFs) remains a major shortcoming when addressing their life cycle impacts. To complement the LCA of TiO₂ -NPs-enabled products under their specific applications, we recapitulated the freshwater toxicity of TiO₂ NPs and then modeled in USEtox to determine trophic level EF ranges under UV and non-UV exposure conditions. Results indicate that EFs derived for non-UV exposure were 52 (42.9-65) potentially affected fraction (PAF) m³ /kg, and combined toxicity data derived EFs were 70.1 (55.6-90.5) PAF m³ /kg. When considering only the UV-induced exposure condition, the modeled EF increased to 500 (333-712) PAF m³ /kg. Our work highlights that case-dependent EFs should be considered and applied to reflect more realistic ecological impacts and illustrate comprehensive life cycle environmental impacts for nanoenabled products. Integr Environ Assess Manag 2023;19:578-585. © 2022 SETAC.