Since the onset of the COVID-19 pandemic in 2020, international tourism has slowly been returning to previous levels. As of July 2024, an estimated 790 million tourists have traveled internationally, marking an 11% increase from the prior year and approaching the frequency of pre-COVID travel (Global Tourism Statistics). While this rise sounds promising for economic stimulation and cultural preservation, it also reintroduces the environmental impacts associated with tourism. In the Mediterranean, for example, tourists seeking to enjoy sunny beach days may unknowingly disrupt local ecosystems through their sunscreen use. Knowing how our consumption and product use impacts environmental systems is a key factor in being able to pinpoint where environmental degradation is coming from, and being able to stop it at the source. This raises the question: do “eco-friendly” sunscreens truly provide a safer alternative?
Pedro Echeveste, a researcher in marine microbial ecology and ecotoxicology at the University of the Balearic Islands, and his team have investigated this topic. Their 2024 study focused on commercial sunscreens and their chemical components’s impact on bacterial communities linked to Posidonia oceanica, or Neptune grass, a foundational species in the Mediterranean ecosystem (Echeveste et al., 2024).
The study examined both heterotrophic bacteria (including Pseudomonas azotifigens, Marinobacterium litorale, Thiothrix nivea, Sedimentiacola thiotaurini, and Cobetia sp.) and autotrophic bacteria (Halothece sp. and Fischerella muscicola), as well as epiphytes—plants growing on the leaves of Neptune grass without being parasitic. These bacterial communities were cultured in artificial seawater at 25°C, with a 12-hour light/dark cycle and an initial concentration of 10^5 bacteria per mL. The research team added various concentrations of nanoparticles and sunscreens (0, 0.01, 0.1, 1, 10, and 100 mg/L) to each sample, exposing the bacterial communities for 72 hours.
Two commonly used inorganic UV filters, titanium dioxide (TiO₂) and zinc oxide (ZnO), were tested due to their prevalence in commercial sunscreens. The study focused on three sunscreen types: an eco-friendly SPF 50 without nanoparticles (SPF50E), an SPF 50 containing TiO₂ nanoparticles (SPF50), and an SPF 90 with both TiO₂ and ZnO nanoparticles (SPF90).
After the 72-hour exposure, the pollution concentrations that led to a 10% population decline (known as the EC10 value) were recorded. Titanium dioxide proved toxic to all heterotrophic bacteria, with Thiothrix nivea exhibiting a 10% decline at a concentration of 3.8 mg/L. Zinc oxide was comparatively less harmful, affecting only Marinobacterium litorale and Pseudomonas azotifigens at an EC10 of 1.39 mg/L for the latter.
The effects varied among the sunscreen types. The eco-friendly SPF 50 reduced phosphorus uptake by 30-50% in most bacterial species, a significant alteration that suggests interference with key nutrient cycles. The regular SPF 50, containing TiO₂, decreased alkaline phosphatase (APA) activity, an enzyme necessary for cell communication via dephosphorylation. Dephosphorylation—the removal of a phosphate group—is a critical process for signal transmission within cells. All sunscreens in the study also led to increased levels of reactive oxygen species (ROS), molecules derived from oxygen that may damage cellular proteins, DNA, and other essential structures. This data allows us to assume that any form of sunscreen, no matter the label as “eco-friendly”, or the SPF value, can impose degradational effects on our environmental systems via one mode or another.
All in all, These findings reveal that eco-friendly labels sometimes lack scientific backing, failing to account for subtle but important factors in maintaining environmental balance. Even the “eco-friendly” SPF 50 sunscreen altered bacterial populations, calling into question the validity of eco-friendly claims.
As tourism resumes in coastal areas, the increased use of sunscreens—and thus UV filters—places greater pressure on marine ecosystems (Raffa et al., 2018). This rise in sunscreen pollution underscores the importance of studying the effects of “eco-friendly” sunscreens, as even minor shifts in bacterial populations can compound into substantial ecosystem changes when multiplied by millions of beachgoers. Achieving a truly eco-friendly sunscreen remains a challenge, but as consumers, what we can do is adopt a more informed and thoughtful approach to product choices. By balancing our personal protection needs with the planet’s health, we can work toward solutions that better align with environmental preservation.
References:
- Un tourism: Bringing the world closer. UN Tourism World Tourism Barometer | Global Tourism Statistics. Available at: https://www.unwto.org/un-tourism-world-tourism-barometer-data#:~:text=International%20tourist%20arrivals%20hit%2096,4%25%20less%20than%20in%202019 (Accessed: 28 October 2024).
- Echeveste, P., Fernández-Juárez, V., Brito-Echeverría, J., Rodríguez-Romero, A., Tovar-Sánchez, A., & Agawin, N. S. (2024). Toxicity of inorganic nanoparticles and commercial sunscreens on marine bacteria. Chemosphere, 364, 143066. https://doi.org/10.1016/j.chemosphere.2024.143066
- Raffa, R.B. et al. (2018) Sunscreen bans: Coral reefs and skin cancer, Wiley Journal of Clinal Pharmacy and Therapeutics. Available at: https://research.ebsco.com/c/ceyvtd/viewer/pdf/db53bg7blv (Accessed: 28 October 2024).