Acute exposure to sunscreen containing titanium induces an adaptive response and oxidative stress in Mytillus galloprovincialis

The use of sunscreens to protect against ultraviolet radiation exposure progressively increases as result of a greater awareness of the people and the greater arrival of tourists. The components of these creams can end up in the waters affecting coastal species. Mediterranean mussels (Mytillus galloprovincialis) were subjected to an acute exposure of a sunscreen with TiO₂ in their composition during 24h. The low and medium concentrations used in the assays contained a concentration of TiO₂ in the range of values found in coastal waters of the Balearic Islands. Titanium and metallothionein concentrations were progressively increasing in gills with the sunscreen concentration in a dose-dependent manner. The activities of the antioxidant enzymes and the detoxification glutathione s-transferase evidenced a hormetic shape response with increased activities at lower sunscreen concentrations, a response that was abolished at the highest concentration. In accordance with these enzyme activities, the levels of malondialdehyde, as a marker of lipid peroxidation, were significantly elevated by the higher sunscreen concentrations. Acetylcholinesterase activity maintained control activities except for the highest sunscreen concentration, where a significant decrease was evidenced. In conclusion, the treatment of mussels with a sunscreen containing TiO₂ in the range of Balearic coastal waters induces an adaptive response that is overcome by the highest concentration. Follow-up biomonitoring studies are necessary to control the concentration of sunscreen compound in coastal waters such as titanium since they can induce oxidative stress to affected organisms.