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  • A Rinconvenient Truth

How reef-safe is that sunscreen?

The current trend with sunscreen – heading in the right direction – is to remove the two main ingredients known to cause damage to coral reefs. What are those ingredients and are they the only culprits? As you read this story, we encourage you to click on the hyperlinks to dig deeper into this topic. Educate yourself and help protect our reefs!

Elkhorn coral, photo by Dr. Hector Ruiz of HJR Reefscaping

For over a decade, scientists have been researching the effects of chemicals found in common sunscreens and documenting their effects on coral reefs. Since a coral is a living animal – and colonies of corals are typically referred to as a “reef” – that eats and reproduces like other animals, they are subject to ingesting chemicals found in their watery surroundings in a similar way that as humans we are exposed to harmful agents in our surroundings like the air we breathe. Lucky for us, we can retreat indoors during particularly harmful smog days, protest to our governments to clean up our air and take care of our own home with closed systems like air conditioning with HEPA filters. Unfortunately, this is not the case for coral reefs which are sessile animals that cannot escape the environment that they (and we) have created. This is why it’s important that we do our part to make sure we are not introducing harmful chemicals into their delicate systems – this includes adamantly checking the ingredients in our sunscreens.

Coral bleaching infographic, developed by NOAA

The two common culprits you may already be familiar with are oxybenzone and octinoxate. These two chemicals are commonly used as UV blockers in cosmetics and sunscreens that reflect the sun’s harmful UV rays and thereby protect your skin from absorbing them. But when these chemicals leach into the water, they cause corals to bleach, or turn white and expose their skeletons. Bleaching happens when the coral ejects its symbiont (an organism living in a mutualistic relationship with the coral) called zooxanthellae which is an alga that provides the coral with essential nutrients. When the coral is under stress – for example, when exposed to harmful chemicals in sunscreens – it cannot support the algae and expels it from the skeleton.

However, recent research has also identified a whole list of other harmful chemicals that we need to watch for in our sunscreens – some of which are even still found in “reef safe” sunscreens.

One of the leading scientists in this research, Dr. Craig Downs, formed a non-profit to look beyond the labels and identify these other ingredients that can be harmful to corals. His organization, Haeretics Environmental Laboratory (HEL), has this list of ingredients on their website:

  • Any form of microplastic sphere or beads.

  • Any nanoparticles like zinc oxide or titanium dioxide.

  • Oxybenzone

  • Octinoxate

  • 4-methylbenzylidene camphor

  • Octocrylene

  • Para-aminobenzoic acid (PABA)

  • Methyl Paraben

  • Ethyl Paraben

  • Propyl Paraben

  • Butyl Paraben

  • Benzyl Paraben

  • Triclosan

Thus, we need to search for sunscreens that are using non-nano ingredients – like non-nano zinc oxide or titanium oxide – which means their ingredients are at least 100 nanometers in diameter, or larger, so that they are not ingested by the corals. The zinc oxide or titanium oxide are the main ingredients that provide the UVA/UVB blocking properties and are also physical UV blockers, rather than chemical blockers; so, they remain on the surface of your skin rather than being absorbed. The debate is still open in regards to if these physical UV blockers are actually safer for coral reefs, and some scientists and environmental organizations actually prefer the term “reef-friendly” to account for this potential impact. In fact, one research group is trying to move away from these two common products and investigate whether algae could be a possible ingredient to reduce sun exposure.

But sunscreen manufacturers are listening and attempting to find a solution that marries the need for sun protection with the critical requirement to protect corals.

For example, local Cabo Rojo-based sunscreen Fango has only five simple ingredients: coconut oil, shea butter, beeswax, red raspberry seed oil and non-nano zinc oxide. “The ingredients are all organic and the beeswax comes from local apiculture”, says Fango spokesperson Monica Maldonado. She states that their development was based on the scientific research already present in terms of their ingredients, but that they tested their recipes until they felt what they had produced the results they wanted to see.

While scientists have been exploring other options for ingredients to introduce into sunscreens, some have been looking into ways to remove sunscreen chemicals from the oceans. Dr. Felix Román of the University of Puerto Rico, Mayagüez and his team have been exploring the addition of chiton/algal microbeads as a way to absorb oxybenzone. But the introduction of microbeads comes with a cost of accidental ingestion by fish or other organisms. However, this was the first attempt to address the potential removal of sunscreen chemicals from coral reefs.

In the end, perhaps nothing is truly “reef-safe” but there are smart choices we can make to reduce our impacts.

  1. Consider wearing SPF-protective clothing. This will reduce the amount of sunscreen you need to apply.

  2. Check ingredients in reef-safe sunscreen to make sure you know what they are and their purpose. Avoid ingredients from the HEL list mentioned above.

  3. Stay away from aerosol sunscreen sprays that easily wipe off as soon as you enter the water.


This article was written by guest contributor Dr. Chelsea Harms-Tuohy, a marine scientist and founder of Isla Mar Research Expeditions in Rincón. Dr. Harms-Tuohy has spent the last 8 years researching our coral reefs and fisheries around the west coast of Puerto Rico, including actively leading and participating in the coral restoration effort at the RMTP following the hurricane and swell event of 2017/2018. Find out more Isla Mar via their website and Facebook.

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