Comprehensive Methodology for Standardized Ecotoxicological Assessment of TiO2-Based Sunscreen Leachates in Aquatic Environment

Roberta Nugnes¹Giulia De Negri Atanasio^2,3Elisabetta Perata⁴Erica Lertora⁴Lorenzo Dondero⁵Federica Robino⁴Francesca Tardanico⁵Cristina Capelli⁶Fabio Ghioni⁶Tania Cai⁶Dalia Gobbato⁶Norina Marciani⁶Roberta Miroglio¹Matteo Zanotti Russo⁴Veronica Piazza⁷Marco Faimali⁷Chiara Gambardella¹Francesca Garaventa^1*Elena Grasselli^2,5,8,9*

• ¹National Research Council, Rome, Italy
• ²Interuniversity Center for the Promotion of 3R Principles in Teaching and Research (Centro 3R), Italy, Torino, Italy
• ³University of Genoa, Genoa, Italy
• ⁴Angel Consulting S.a.s, Milano, Italy
• ⁵Department of Earth, Environment and Life Science, University of Genoa, Genoa, Italy
• ⁶Agenzia Regionale per la Protezione dell'Ambiente Ligure, Genoa, Italy
• ⁷National Research Council, Roma, Italy
• ⁸National Center for the Development of New Technologies in Agriculture (Agritech), Napoli, Italy
• ⁹Istituto Nazionale Biostrutture e Biosistemi, Rome, Italy

This study evaluates the ecotoxicity of micro-and nano-sized titanium dioxide (TiO2), either as active ingredients or incorporated into sunscreen formulations in the aquatic environment, by proposing a leaching protocol simulating a realistic scenario of human immersion in freshwater and seawater. To this aim, an ecotoxicological screening of micro-and nano-TiO2 active ingredients and incorporated into sunscreens was applied, by evaluating acute and sub-acute responses (bioluminescence and growth inhibition, immobilization, behaviour) in freshwater and marine bacteria, microalgae and crustaceans. Then, Ti concentration was measured in the leachates of sunscreens through Inductively Coupled Plasma mass spectrometry (ICP-MS). Toxic effects (EC50s) were only found in microalgae and crustaceans exposed to TiO2 active ingredients. No toxicity occurred with sunscreens formulations, although significant algal growth inhibition was determined, likely due to TiO2 size rather than Ti concentration. This study promotes a sunscreen leachate-based methodology coupled with a multi-species and multi-endpoint ecotoxicological approach to assess the toxicity of TiO2-based sunscreens in freshwater and marine environment, supporting the development of more effective regulations to protect the aquatic ecosystem. By integrating a sunscreen leachate-based methodology with a multi-species and multi-endpoint approach, this study introduces a novel ecosafety-oriented assessment of TiO2 providing realistic ecotoxicological evidence relevant to freshwater and marine environments.