What is the impact of sunscreens on the sea?

By now we have learned that it is absolutely necessary to use creams to protect ourselves from the harmful rays of the sun, in order to avoid painful sunburns and prevent long-term damage to our skin. But we must be careful when buying cream: the impact of sunscreens in the sea can create damage to some species.

Why do sunscreens harm the ocean?

Several studies have shown that sunscreens have a strong impact on the health of our ocean and many of its inhabitants. It is no coincidence that several tropical destinations where there is a consolidated coastal and maritime tourism market have banned their use. A striking example is that of the Government of Hawaii, which in 2018 issued the Hawaii Reef Bill, to ban the use of sunscreens containing certain chemical substances considered harmful to the marine ecosystem.

Specifically, sunscreens:

• can alter the growth and photosynthetic process of green algae;
• can accumulate in coral tissue, causing bleaching, genetic and physical alterations of the coral, or even causing its death;
• can cause malformations in the larvae of young molluscs;
• can damage the immune and reproductive systems of sea urchins or cause their death;
• can reduce fertility and generate male organs in female fish (this alteration is called “imposex”, which means superposition of male characteristics to the female ones present in females);
• can accumulate in the tissues of dolphins and transfer this accumulation of chemical compounds to their offspring.

Harmful chemicals in sunscreens belong to the UVF category, or ultraviolet filters, which are needed to absorb and reflect UV-A and UV-B rays. These substances are both organic (e.g. benzophenones, p-aminobenzoates, and camphor) and inorganic [e.g. nanoparticle oxides: titanium dioxide (TiO2) and zinc oxide (ZnO)]. Sunscreen components enter the marine environment, dispersing both in the water column and in sediments, as a result of direct input from swimmers but also, indirectly, through domestic and industrial wastewater discharges. These emerging pollutants are so widespread that they are also starting to affect freshwater bodies such as rivers and lakes.

Posidonia oceanica: How sensitive is this Mediterranean marine plant to sunscreens?

Some polluting sunscreens such as oxybenzone (BP3), 4-methylbenzylidene camphor (4-MBC), methylparabens, avobenzone 4-methyl, benzophenone (BP4), benzotriazole (MeBZT) have also been found in the fronds and rhizomes of Posidonia oceanica. Posidonia is a marine plant endemic to the Mediterranean that extends in large meadows and provides numerous ecosystem services: it is home to many marine species, especially in the juvenile phase, provides protection from coastal erosion and sequesters carbon dioxide from the atmosphere.

The accumulation of these toxic substances within Posidonia has effects that are still uncertain, but researchers are already alert to the possible consequences both at a physiological level – such as alterations in reproductive processes and photosynthesis – and at an ecosystem level -.

Considering the conformation of the Mediterranean Sea as a semi-closed basin with reduced water recirculation, the levels of pollutants can reach high concentrations in a short time. Also to be taken into account is the strong anthropic pressure present in this area given by industrial activities and tourism, the introduction of nutrients and heat waves that suddenly increase the temperature of the water. All these factors can produce synergistic effects, putting the survival of this marine plant to the test.

Given the key importance of Posidonia in this ecosystem, it is good to spread awareness related to the environmental damage caused by these pollutants contained within sunscreens, regulating their use and providing sustainable alternatives for the protection of bathers. The loss of Posidonia meadows has already proven to be highly damaging in several coastal areas, we must act to protect it.

Beware of greenwashing and bluewashing!

Despite the emergency caused by these products, there is still no clear legislation regarding the use of harmful sunscreens in many parts of the Mediterranean. With the media attention that the ocean and the topic of sustainability in general are finally receiving, some brands are leveraging these issues, putting creams on the market that are “safe for the coral reef”. In fact, the absence of oxybenzone is guaranteed, but these products still contain other sunscreens that are harmful to the marine ecosystem. For this reason, it is important to read the INCI carefully and not just trust a sticker on the package.

What can we do?

It is crucial to inform yourself before purchasing. In addition to purchasing ocean-friendly creams, therefore free of the chemical compounds mentioned above, a simple example to follow to reduce the consumption of sunscreens and reduce the impact on the marine environment is to avoid the hottest hours and protect yourself from the sun with umbrellas, or by wearing specific clothing even while swimming in the sea.

Bibliography:

• Nona S.R. Agawin, Adrià Sunyer-Caldú, M. Silvia Díaz-Cruz, Aida Frank-Comas, Manuela Gertrudis García-Márquez, Antonio Tovar-Sánchez, Mediterranean seagrass Posidonia oceanica accumulates sunscreen UV filters, Marine Pollution Bulletin, Volume 176, 2022