This article is part of our Beauty and Cosmetics feature: discover it here

With summer approaching, we see the return of ad campaigns, social media tips and warnings on sunscreen. Dermatologists and health authorities, on one hand, continue to stress the importance of UV protection; on the other, content describing UV filters as “toxic” ingredients is on the rise. Meanwhile, attention is growing regarding the environmental impact of sunscreens on marine ecosystems, particularly coral reefs. The result is an often confusing debate, where scientific data, oversimplifications and fears lacking context risk becoming intertwined.

UV filters: the difference between chemical and physical

UV filters shield your skin from ultraviolet radiation, the main cause of sunburn, premature skin ageing and skin cancer. In 2024, scientists at the International Agency for Research on Cancer (IARC) estimated that over 80% of skin melanoma cases diagnosed in 2022 could be attributed to UV exposure.

Sunscreens fall into two main categories: chemical and mineral. “Chemical UV filters, also known as organic filters, are carbon-based compounds that absorb ultraviolet radiation, converting it into heat,” explains Gianluca Selvestrel, head of the Environmental Sustainability Unit for Industrial and Healthcare Systems at the Mario Negri Institute for Pharmacological Research, to Renewable Matter. “Among the most common are avobenzone, octocrylene, homosalate, octinoxate, oxybenzone and octisalate. Added to these are new-generation filters such as Tinosorb S, Tinosorb M, Uvinul A Plus and Uvinul T 150.”

Mineral, or physical, filters, on the other hand, function by creating a barrier that reflects and scatters part of the UV radiation: the most commonly used are powders, such as zinc oxide and titanium dioxide.

Health risks: what does science say?

Concerns for human health stem from the fact that “some chemical UV filters may have potential adverse effects,” continues Gianluca Selvestrel. “These ingredients can be absorbed systemically, reaching concentration levels in the blood that exceed the limits considered safe. Some studies suggest effects on the endocrine system, such as alterations to thyroid and reproductive hormones.”

One of the most cited studies is the one published in 2019 by the Food and Drug Administration (FDA), which found traces of organic UV filters in participants’ blood – specifically avobenzone, oxybenzone, octocrylene and ecamsule – following repeated applications of sunscreen, at concentrations exceeding the threshold beyond which the FDA requires further toxicological testing. The researchers themselves, however, pointed out that the study was not intended to discourage the use of sun protection. According to Brian Diffey, professor emeritus of photobiology at Newcastle University, the study was based on “maximum use conditions”, with quantities far exceeding those normally applied in everyday life, as reported by the Guardian.

Benzophenones, including oxybenzone, have long been studied for their potential effects on the endocrine system, fertility and development, as reported in a review study on the evidence that emerged between 2014 and 2024. The authors nevertheless stress the need for more robust data and long-term studies.

Impact on marine ecosystems

UV filters reach our seas and oceans when we go swimming, but they can also enter the water through urban drainage, industrial effluent and sewage treatment plants, as they are present in various products – from paints to plastics – as well as in cosmetics. “Among the most discussed environmental impacts is their possible contribution to coral bleaching, but they can also alter larval development, cause oxidative stress and be toxic to algae, fish and invertebrates,” explains Selvestrel.

Coral bleaching is a global phenomenon that has considerably increased over the last twenty years, and several studies have been conducted on the subject, highlighting how oxybenzone can damage coral DNA and promote bleaching, leading to Hawaii's decision to ban oxybenzone and octinoxate in sunscreens. This example was subsequently followed by the US Virgin Islands and certain reserves in French Polynesia.

Even in this case, however, the issue remains complex. Numerous researchers emphasise that sunscreens cannot be considered the sole cause of the problem, which also depends on rising ocean temperatures, pollution and human pressure.

Mineral filters and nanoparticles

Mineral filters are often presented as the safest and most sustainable alternative, both for health and the environment, as they tend to remain on the skin’s surface without being absorbed to any significant extent. They are not without their drawbacks, however, especially when zinc oxide and titanium dioxide are used in the form of nanoparticles to improve the transparency and texture of sun creams.

“These extremely small particles can aggregate, settle and interact with organic matter in the water, favouring the formation of reactive oxygen species under certain conditions,” adds Selvestrel.

To help you make your choice, look for the label “non-nano” on the packaging, which indicates larger particles, deemed less problematic. However, there are still many factors to consider when choosing sun protection: you need to assess the product’s overall composition, relying on official certifications and avoiding oversimplifications.

How to pick a sunscreen

“The biodegradability and persistence of other ingredients – such as fragrances, preservatives, silicones, film-forming polymers and microplastics – which may be irritants or harmful to the environment must also be taken into account,” Selvestrel emphasises. “Furthermore, water resistance is important, although caution is needed: on the one hand, it helps reduce the release of lotions into the water, as they adhere better to the skin; on the other, it may require more persistent polymers or film-forming agents.”

As for packaging, “it is advisable to opt for recycled and recyclable materials, favour refill formats, and reduce secondary packaging.” The format also matters: “It is best to avoid using sprays near beaches, especially in windy conditions, as this increases dispersion into the environment and the risk of inhalation by people.”

Finally, sustainability also requires correct use: various measures, such as applying the lotion according to the recommended timing before entering the water, avoiding unnecessary excess, and supplementing protection with hats, sunglasses and clothing, whilst avoiding exposure to the sun during the hottest hours of the day, can help reduce environmental impact without compromising safety.

Legislation and research: what to expect

From a regulatory perspective, “the European Union only approves UV filters listed in Annex VI of the Regulation on cosmetic products, which can be used under specific limits and conditions,” explains Selvestrel. “However, the primary focus remains on human health, whilst environmental impact is considered only marginally.”

In the meantime, several countries are introducing restrictions or requesting additional data from manufacturers: “In the United States, for example, sunscreens are regulated as OTC products and therefore as pharmaceuticals.” The UK’s Office for Product Safety and Standards plans to tighten oxybenzone limits in 2026, bringing them into line with European standards, while in Australia, the Therapeutic Goods Administration (TGA) has recommended reformulating sunscreens and implementing further safety measures for various chemical compounds, including, once again, oxybenzone.

Looking ahead to the future of research, “we will certainly see the emergence of the next generation of filters, offering greater stability, broad-spectrum protection and enhanced effectiveness,” concludes Selvestrel. “It remains essential, however, to explore the issue of environmental impact in further depth, as this is one of the areas requiring the most study, so that scientific evidence can then be translated into appropriate regulatory measures.”

Sun protection therefore continues to be an essential tool for safeguarding health, and even the experts on the European Scientific Committee on Consumer Safety (SCCS) consider UV filters to be safe when used in accordance with the recommended doses and methods. The challenge today, therefore, is to make sun protection increasingly transparent, safe and compatible with marine ecosystems.

Cover: Envato image