By Roberta Maria Serra
Mentorship Paulo Lima
Some sunscreens release UV filters that can harm corals and marine ecosystems. Growing attention is being paid to more sustainable alternatives and eco-friendly sun-protection practices.
With the arrival of summer, the days get longer, temperatures rise, and we start spending more time outdoors again, at the beach, with friends and family. And, inevitably, a few too many sunburns also make an appearance.
The use of sunscreen is an essential tool for protecting the skin from damage caused by ultraviolet radiation. In recent years, however, scientific research has brought to light a lesser-known aspect: the impact that some UV filters can have on marine ecosystems.
The issue requires an important premise, however: sunscreens should not be demonized. Alongside other protective strategies, such as sunglasses, hats, and lightweight, breathable UV-protective clothing, they are currently among the most effective tools for reducing damage caused by sun exposure, limiting the risk of melanoma and counteracting premature skin aging. The issue, therefore, is not sun protection itself, but the need to better understand the impact of certain formulations and promote more sustainable choices.
The tangible effects of sunscreens on marine biodiversity
The UV filters contained in sunscreens do not, in fact, remain confined to the skin. During swimming, some of these substances are released into the environment. The phenomenon is particularly significant in heavily visited tourist areas, where the simultaneous presence of thousands of swimmers leads to a continuous accumulation of these substances in coastal waters.
Estimates indicate that between 6,000 and 14,000 tonnes of sunscreen reach marine ecosystems every year, with the most significant effects occurring in coral reef areas. Corals are extremely delicate organisms that live in symbiosis with microalgae known as zooxanthellae, which are essential to their nutrition and survival. Some chemical filters, such as oxybenzone and octinoxate, can disrupt this biological balance and induce coral bleaching. During this process, corals expel their zooxanthellae, thereby losing a vital source of energy and becoming progressively more vulnerable.
The observed effects of sunscreens on marine flora are not limited to bleaching. Several studies suggest that these substances may promote the activation of latent viral infections in symbiotic algae, accelerating their destruction. Oxidative stress, genetic alterations, and interference with essential biological processes such as photosynthesis have also been detected. The most vulnerable stages of the life cycle are particularly exposed: larvae and developing organisms may suffer deformities or have lower chances of survival. In ecosystems already under significant pressure, such as from rising sea temperatures linked to climate change, these factors may further aggravate already critical conditions.
Some progress in the laws of countries with high levels of tourism
Growing attention to the issue has led some parts of the world to introduce regulatory measures. Places such as Hawaii, Palau, and the U.S. Virgin Islands have introduced restrictions on the sale of products containing oxybenzone and octinoxate, recognizing the connection between the presence of certain UV filters and the deterioration of coral ecosystems.
In the search for more sustainable alternatives, mineral-based products containing zinc oxide or titanium dioxide have become increasingly widespread. These filters are often presented as more environmentally friendly options, but the issue remains complex. Some formulations containing nanoparticles could, in fact, pose problems for aquatic ecosystems. Ultrafine particles can interact with sensitive marine organisms and, under certain conditions, contribute to environmental toxicity.
But what can we do to improve the situation?
For this reason, individual behavior can make a tangible contribution to reducing environmental impact. A first step is to pay greater attention to the ingredients listed on labels. Experts suggest avoiding compounds such as oxybenzone, octinoxate, and butylparaben, substances considered particularly problematic for marine ecosystems and already subject to restrictions in several parts of the world.
Small everyday actions can also make a difference. In some protected areas, such as several Mexican cenotes, visitors are asked to shower before entering the water to remove sunscreen residues and other cosmetic products from their skin. This is a simple practice that reduces the amount of substances released directly into the environment. Likewise, wearing UV-protective clothing, such as shirts and hats, can help reduce the amount of sunscreen needed while also limiting exposure to sunlight.
At the same time, several researchers emphasize the importance of investing in the development of UV filters that are genuinely biodegradable and free from toxic effects throughout the marine food chain.
Sun protection remains essential and is an indispensable public-health measure. The challenge, rather, is to find a balance between protecting human health and safeguarding marine ecosystems through a combination of scientific innovation, more conscious behavior, and more effective environmental protection policies.
To stay on the summer theme
As summer approaches, we recommend reading articles that explore the warm season from different perspectives: But how hot is it in this city? explores the phenomenon of urban heat islands, Dolomites Under Siege: The Price of Overtourism Amid Fragility and Risk discusses overtourism in the Dolomites, and Boiling Brains: How Extreme Heat Changes Our Minds (Literally) examines how extreme heat can also affect mental health.