Multigenerational exposure to nano‐TiO₂ induces ageing as a stress response mitigated by environmental interactions

Despite their ubiquity in personal care products, the health implications of titanium dioxide (TiO₂) nanomaterials (NMs) are under strenuous investigation for their potential as a carcinogen, whereas other evidence has shown links with premature ageing. Both potential hazards are manifested after chronic exposure. To explore the chronic effects of TiO₂ NMs in the environment, a multigenerational study using the model test species Daphnia magna is conducted. Phenotypical characteristics associated with ageing are observed (loss or shortening of tails and lipid accumulation) with increased expression of highly conserved key stress response genes involved in inflammatory responses and oxidative stress. These responses are visible in continuously exposed daphnids over four generations and in daphnids removed from maternal exposure even three generations later. However, exposure to the “aged” variants of these NMs at the same concentrations significantly reduced these effects, and exposure in medium containing natural organic matter is less severe than in salt-only medium.