Ultraviolet radiation (UV) is a fundamental risk factor for the development of nonmelanoma skin cancer and it is also implicated in the pathogenesis of melanoma.1–6 UV radiation is also associated with premature skin aging.4

Photoprotection is the main preventive strategy for reducing the risk of developing skin cancer and achieving healthy aging. Given that skin cancer is the most prevalent cancer in the Caucasian population, the importance of photoprotection is beyond question.7 In recent years, the use of sunscreens as become widespread as an essential component of photoprotection, particularly in Western countries.8 Sunscreens can be classified as organic, inorganic, and biological according to their mode of action.9 Organic filters are the most widely used and can protect against both UVA and UVB radiation.1,10 The sunscreen formulas available on the market usually include a mixture of organic and inorganic filters with 20 or more components to ensure sufficiently broad spectrum coverage.11,12 In addition, these sunscreens include other types of product such as perfumes, hair tints, and plastics.

In recent years, studies have reported accumulation of UV filters in different ecosystems and the toxic effect these can have on many of them. This is due not only to the widespread use of sunscreens in certain environments such as beaches but also because some filters are not readily eliminated with habitual techniques used in wastewater treatment plants, thus contaminating water released to rivers and seas.13–16

Substantial quantities of UV filters such as benzophenone 3 (BP-3) and ethylhexyl salicylate (EHS) have been detected in different water sources and sediments (rivers, beaches, seas, lakes, etc.) throughout the world.17 Moreover, some studies suggest that the UV filters can persist for a long time in water and sediments, and that seas and currents can transport them over large distances.18,19 Also, as might be expected, many of these compounds such as octocrylene (OC) and BP-3 are also found (sometimes at very high concentrations) in living organisms such as algae, corals, fish, and even mammals. Thus, there is a growing body of evidence on the toxic effect of UV filters in these organisms, with the potential to cause problems in the food chain20 and therefore also impact the environment in general.14

Currently, we should also be keenly aware of the effects of global warming. On one hand, the mean temperature of water is increasing, with a negative impact on many ecosystems, particularly marine ones. On the other, there is an increasing number of sunny days throughout the world, and this may lead to an increased use of UV filters, with the subsequent accumulation of sunscreen products and greater toxicity for affected ecosystems.20

In view of the above, the main objective of this study was to perform an exhaustive and critical review of the evidence available on the environmental impact of UV filters.

We undertook an extensive narrative review of the literature from different databases to analyze the existing evidence about the impact of UV filters on the environment. The following inclusion criteria were defined: (1) Articles that analyze UV filters (regardless of type of filter and composition); (2) articles that report the impact of these products on the environment (flora, fauna, food chain, water, etc.); (3) no restrictions were applied for the outcome variable; and (4) any study design was accepted, except for opinion articles. Articles published in any language other than English or Spanish were excluded.

The following literature databases were analyzed from their creation through July 2021: Pubmed, Dialnet, Advanced Google, and Trip. Different search strategies were applied was for each one of these, in which both controlled and free language with key words such as photoprotection, environment, future, or filters UV were used.

The articles were selected in 3 phases, which were conducted by a single reviewer. In the first step, the citations retrieved by the search strategies were screened by reading the title. All those that did not meet the inclusion criteria were eliminated. The remaining citations were then screened using the abstracts. Finally, the selection process was completed with a detailed reading of each article. Those that met the inclusion criteria were definitively accepted. Finally, a secondary search was performed of articles included through reading of the reference list of the retrieved articles.

The same reviewer who selected the articles compiled data on the studies included. The quality of the studies included was assessed using the 2011 Oxford scale.21 The evidence and the findings were tabulated.

A qualitative synthesis of the compiled data was then undertaken.

The literature review undertaken has evidenced firstly that UV filters have accumulated in different media, such as water and sediments, and also in different organisms. This is probably due to different factors; one of these is the massive use in recent years of UV filters. It is estimated that 10000 tons of UV filter are produced a year for the global market.12 Some of these filters possess structural and physical-chemical characteristics that hinder biodegradation, with the subsequent risk of bioaccumulation. This accumulation in water may occur directly, for example, with bathers on a beach (in fact, beaches are the areas where the highest concentrations of UV filters are usually found) or indirectly, given the limited capacity of wastewater treatment plants for filtering them out of wastewater.13–16

On the other hand, our review draws attention to the toxic capacity of some of these filters, above all BP-3 and OC in multiple organisms; this is often dose-dependent, particularly in the case of in vitro exposure.22,26–44 In vivo toxicity has also been found, although to a lesser extent.11,15,25 On this point, we want to highlight that study of environmental impact is very complicated (methodological limitations, very complex ecosystems, dynamic phenomena, etc.) and so these results should be treated with caution. However, although the toxicity detected in the field is not very high, taking into account that the use of filters will likely increase, it is possible that we will see greater damage on reaching higher concentrations of UV filters.

In a recent study, blood concentrations of different sunscreens (BMDBM, BP-3, OC, HS, EHMC, and ethylhexyl salicylate) were found to be in excess of 0.5ng/mL after a single application of sunscreen; currently, the clinical implication in terms of carcinogenicity and/or impact on reproduction is not known. Moreover, given that these filters have a long half-life, usually greater than 48h, repeated use means they can be detected in blood up to 17 days after the last application.52,53 Similarly, although UV filters or their derivatives may reach humans via the food chain, to date, there have been no reports of toxic effects.

Faced with this situation, a range of actions are available to ensure use of UV filters with appropriate photoprotection, essential for preventing skin cancer and skin aging, and also free of environmental impact.

One of the first actions would be to set up a regulatory framework, banning compounds that are shown to be toxic for the environment. Along these lines, some of the most harmful UV filters such as EHMC and BP-3 are already banned in some places, such as Palaos or Hawaii, due to the potential deterioration to coral reefs, one of the main tourist attractions for these places.16

In addition, although it is true that in Spain it is only possible to use UV filters listed in Regulation (CE) 1223/2009 of the European Parliament and Council,54 which should also be used according to the indications for each of them, personal care products (PCPs) can include UV filters, but they do not require environmental study, even though they are considered emerging contaminants.

Also, the lack of standardization in terms of concentrations that may be toxic for the environment, or the lack of definition as to what a biodegradable product is or what constitutes protecting the environment or respecting the oceans means that the packaging often includes information that is inadequate, confusing, or even incorrect.

Change is needed urgently, both in the formulation of the product, aiming to minimize the environmental impact while guaranteeing photoprotection, and in the water purification methods of the wastewater treatment plants. Of importance is that manufacturers of the commercial brands of PCPs with UV filters are aware of the potential negative effects of these filters in the environment. Thus, research institutions and the cosmetic industry should make more effort to identify new molecules to use as UV filters, or mixtures or specific concentrations to provide the necessary photoprotection while having a low environmental impact.

Scientific societies, headed by the Spanish Association of Dermatology and Venereology, should continue in their efforts to raise awareness of the importance of photoprotection. Adequate photoprotection strategies should be multifactorial rather than relying on a single intervention. For example, using photoprotective clothing and swim gear, applying sunscreen to areas exposed to sunlight, limiting exposure times, and taking care with reflective surfaces should all be considered. It should be highlighted that the findings described above do not contradict these photoprotection strategies.

Sunscreens have evolved to better fit the individual needs of individuals, taking into account their age, skin type, presence or risk of diseases, as well as different activities performed by these people.20 It is to be hoped that sunscreens will be improved with increasingly environment-friendly formulations. For this, the strength of evidence, standardization of procedures, and regulations will need to be improved.

The authors declare that they have no conflicts of interest.