Nanoparticles based sunscreens provoke adverse effects on marine microalgae Dunaliella tertiolecta

Abstract

Sunscreens represent one of the main sources of engineered TiO₂ and ZnO nanoparticles (NPs) in coastal ecosystems, especially during the summer period. To understand the effective environmental impact of NPs in commercial sunscreens, this study assesses the effect of TiO₂ and ZnO NPs extracted from three commercial products (S2; S10; S11) upon marine microalgae Dunaliella tertiolecta by evaluating its growth inhibition, oxidative stress and DNA damage. Algae were exposed to both the sunscreen formulations containing NPs and a sunscreen without NPs. Results showed that algae growth inhibition was affected by the extracted NPs (EC20 S2: 9.2 mg Ti L⁻¹; EC20 S10: 0.49 mg Ti L⁻¹; EC20 S11: 14 mg Ti L⁻¹), and the algae was generally biostimulated by the sunscreen formulations, due to the presence of other components that could enhance algal growth. Among the sunscreens containing NPs, relevant effects, mainly as ROS production and DNA damage, were evidenced when both TiO₂ and Zn were present (S10; S11). Moreover, lower effects were always observed for the sunscreens and the corresponding extracts, compared to the effects of industrial NPs. These findings suggest that the product formulation may mitigate toxic effects of NPs either by direct modification of properties or by providing organic and inorganic nutrients that biostimulate microalgae growth. The NPs extracted from sunscreens showed responses that cannot be predicted solely from the response of industrial nanoparticles, suggesting that the aging in sunscreens can influence the final toxicity of nanoparticles. In conclusion, the adverse effects of sunscreens upon microalgae could not be solely attributed to the NPs, but also to the combined action of multiple components.