by Ashleigh Papp

As we inch towards the longer days and warmer nights, the summer months seem to hang in front of us like a lure on a string. I find myself daydreaming about that feeling of the sunshine being absorbed into my skin and almost immediately following, I remind myself about sunscreen. Whether you’re light skinned or dark, young or old, we all know that the crispy red skin of a sunburn is something to be feared and that the best way to avoid it is prevention. But this summer, as I begin to plan my beach escapades and pack up my bags, I find myself thinking more about what I put on my skin and the effects it might have on the environment.

For thousands of years, humans have spent time outside in the sun. However, only recently did scientists and doctors begin to realize that prolonged exposure to the sun could cause long-term damage to one’s skin. Invented in the late 1930s, sunscreen quickly became a household item that no parent would let their children leave home without. Equipped with chemicals powerful enough to absorb or deflect the harmful UV rays of the sun, the protectant was deemed safe for human use about 40 years later. Finally, we could go to the beach and play in the sun all day—just as long as we remembered to re-apply the sunscreen.

But then, about 5 years ago, researchers in Hawaii began to notice something strange — not to those who were applying the protective cream to their bodies, but to the water beach-goers inevitably entered on hot summer days. The health of coral reefs and marine wildlife in nearby coastal areas began to decline, especially in the more heavily trafficked tourist areas. The researchers began to collect samples of surface water and surveyed the health of nearby coral reefs and marine wildlife. Their findings were shocking in a way that really shouldn’t have been: sunscreen ingredients, when applied to coral reefs in a lab, led to deformation and immobility in the tiny creatures that kept the reef alive. What we put on our skin winds up in the water — and sunscreen, without exception, is one of those things. What started as a miraculous cream used to prevent skin cancer is actually causing harm to the very wildlife that drew us to the beach in the first place.

The way sunscreen works is simple yet complex. It protects our skin in two major ways — by either absorbing or deflecting ultraviolet (“UV”) rays from the sun. But, in order to better understand how sunscreen can hurt coral reefs, we have to dive deeper into the ingredients and how they work to protect us.

The first group, which absorbs some of the harmful rays, works by triggering a cascade of events that break down the UV rays into a non-harmful form of light. This process is called “photo-degradation” and while it’s helpful in protecting our skin, it also results in a molecule with a leftover, unpaired electron. In general, electrons would much rather be in a pair, so this singular charge, known as a free radical, becomes reactive and can have a big impact on the health of a coral reef.

The other group of active ingredients in sunscreen deflects UV rays altogether. These are powerful compounds that contain metal and once they are in the presence of light, they begin to break down into metal ions, or smaller unstable pieces of the metal compound. Once in the ocean, these disrupt the energy-creating process that constantly goes on inside coral reefs, leading to what scientists call oxidative stress. The magical formulation of sunscreen packs a powerful punch.

But how do these ingredients lead to actually harming a coral reef?

Let’s talk about how a healthy coral reef works.

Imagine the most beautiful piece of coral you’ve ever seen — lush, wildly colorful, and swaying in the soft ocean current. This beautiful thing is actually not one, but two creatures that live in harmony together. Biologists call this symbiosis and it can be seen in many different ways across environments. From clownfish living in a poisonous anemone to microorganisms thriving in our digestive tract, the general idea is that each party provides something useful to the other so that they become dependent on one another to survive. Without its partner in crime, the coral, made up of calcium carbonate, is white and skeleton-like. It is the other piece of this beautiful puzzle, algae, that provide the vibrant hues we’ve come to associate with a coral reef. The algae are capable of photosynthesis, meaning it uses light to turn carbon dioxide into oxygen and sugar. The coral then uses the oxygen and sugar generated by the algae to survive and gives off carbon dioxide as a waste product, which the algae use to start the cycle all over again. In a stable environment, this partnership can withstand the trials and tribulations of the ocean, but the introduction of sunscreen pollutants has been found to disrupt their normally functional relationship.

The free radicals from the UV absorbing ingredients in sunscreen and the metal ions from the UV deflectors impact the health of the coral in different ways, but their presence leads to the same result — a stressed out coral reef. As this begins to happen and the immune system is weakened, the coral reef can no longer fight off the viruses that regularly float through the ocean. Similar to how an airborne virus gets passed around the office during the cold and flu season, waterborne viruses are common in water as well. Similarly to humans, if a coral reef is healthy, it can protect itself via a normal immune response. However, adding harmful sunscreen chemicals into the ocean can so greatly disrupt the natural processes of the coral and its algae that their immune systems become too weak to survive. Without a change in our beachside behavior, the colorful algae as we know it today may eventually either die or be dejected, leaving behind only the white skeleton-like shell of the coral.

The effects of sunscreen are still being studied in coral reefs and beyond. However, there are many compelling experiments that suggest our use of this protectant is influencing the health of our beloved coastlines. Experiments are already underway to learn more about certain coral reef species that can prevail despite toxic sunscreen runoff. And, research does suggest that coral reefs may be able to rebound if environmental stressors are removed.

How to protect your skin from the sun — without hurting coral reefs:

Rest assured, effective sunscreen that isn’t known to harm coral reefs is available! As you plan for the next beach day, try any of the following tips to ensure you’re doing everything you can to protect our coral reefs:

• Wear a t-shirt or rash guard instead of lathering up. These can provide just as effective sun protection as sunscreen without the consequences.
• Avoid using sunscreen that contains a mention of any of the following ingredients: Parabens, Camphor, Oxybenzone, Cinnamate, Benzophenone, Titanium dioxide, or Zinc oxide.
• Keep in mind that an aerosol sunscreen spray is far more likely to travel into the water than a cream or lotion.
• Talk about it with your fellow beachgoers and even local legislators! Most don’t realize that our sunscreen can be seen as part of the problem.

It’s tough to say how a decline in coral reef health will affect our oceans overall. Based on our current understanding of how vital these systems are to the rest of an ocean’s wellbeing, it is safe to say we should start paying attention. Coral reefs are only one of the many documented cases of marine inhabitants that are negatively affected by sunscreen pollution. This summer, as you pack up your beach bag and head out to the coast, think about what it is you can do to protect not only your own health, but also that of our beloved oceans.

Source(s) Cited

Basterretxea, G., Benedé, J., Blasco, J, Chisvert, A., Moreno-Garrido, I., Salvador, A., Sánchez-Quiles, D., Tovar-Sánchez, A. (2013). Sunscreen Products as Emerging Pollutants to Coastal Waters. https://doi.org/10.1371/journal.pone.0065451

Danovaro, R., Bongiorni, L., Corinaldesi, C., Giovannelli, D., Damiani, E., Astolfi, P., Greci, L., Puceddu, A. (2008). Sunscreens Cause Coral Bleaching by Promoting Viral Infections. Environmental Health Perspectives, 116(4): 441-447. https://doi.org/10.1289/ehp.10966

Downs, C.A., Kramarsky-Winter, E., Segal, R. et al. Arch Environ Contam Toxicol (2016) 70: 265. https://doi.org/10.1007/s00244-015-0227-7

Ashleigh Papp is a science writer based in San Francisco, CA.

When not reading or writing, she spends her time playing outside with friends or inside with her cat, Sandy.