The Science of Sunscreen

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The Science of Sunscreen: How to Protect our Coral Reefs

Types of UV Radiation

UVA – Wavelength 320 – 400 nm

This makes up 95% of solar UV radiation that reaches the Earth’s surface. It penetrates the deepest into the skin. This can cause wrinkles and is a contributing factor in developing skin cancer.

UVB – Wavelength 290 – 320 nm

The remaining 5% of solar UV radiation reaching the Earth’s surface - this kind causes direct DNA damage and is one of the main contributors to skin cancer.

UVC – Wavelength 100 – 290 nm

This kind of radiation doesn’t get past Earth’s atmosphere and therefore does not contribute to skin cancer.

What UV Blockers are used in Sunscreen?

There are two different types of sun-blocking ingredients in sunscreen, physical and chemical. 

The physical blockers are typically one of two active ingredients, Titanium Dioxide and Zinc Oxide. These tiny mineral particles sit on top of your skin and deflect UV rays.

Titanium Dioxide (O=Ti=O): Titanium dioxide is produced as an ultrafine (nanomaterial) product, resulting in transparency, or non-nano, resulting in a greyish-white residue when applied to the skin. It blocks short wave UVA and UVB light absorption.

Zinc Oxide (Zn=O): Zinc oxide, like Titanium Dioxide, is also produced as nanomaterial (transparent) or non-nano (greyish-white). However, it is more effective than titanium dioxide as it blocks both long and short UVA waves and all UVB waves.

What about Chemical Blockers?

The most commonly used chemical blockers in the United States are aminobenzoic acid, avobenzene, octisalate octocrylene, octinoxate and oxybenzone. These chemicals block varying degrees of UVA and UVB. Chemical UV blockers are currently more popular than physical UV blockers because they’re absorbed into the skin without leaving a white residue and feel relatively weightless. However, despite being absorbed into the skin, some of these chemicals still wash off when they are worn in the ocean. Oxybenzone, for example, is found in approximately 60% of all sunscreen used today, and is one of the most thoroughly studied chemicals in sunscreen. Studies have shown that chemical UV blockers like oxybenzone are causing serious damage to marine life and coral reefs.

What is safe for our Coral Reefs?

It has recently been determined that all nano-particle size UV blockers are unsafe for the ocean, and that the UV-filtering chemical blockers oxybenzone and octinoxate are contributing to the bleaching of our coral reefs. As a rule of thumb, sunscreen that doesn’t leave a white residue on your skin is probably using nano-particles instead of large-particle physical UV blockers, endangering the marine environment.

Key things to look for when purchasing sunscreen

  • Sunscreen that does not contain oxybenzone and octinoxate
  • Mineral based sunscreen with physical blockers Zinc Oxide and Titanium Dioxide
  • Check for nano ingredients - Ingredient particles should be larger than 100 nanometers so coral cannot ingest them
  • When is doubt, look for a reef-safe label!

Why is this important?

Coral Reefs provide shelter and habitats for some of the most diverse ecosystems on the planet.  The fishing industry depends on them because fish spawn there and grow before heading out to sea. NOAA estimates coral reefs’ economic value—which accounts for several factors including tourism and food production—to be in the realm of $30 billion annually.

When Coral Reefs become bleached they no longer produce the nutrients that the marine life needs to survive and stop assisting in carbon and nitrogen fixing. Combined with global warming, which also plays a role in Coral Reef bleaching due to warming oceans, we risk extinction of important marine life.

We have a chance to make a difference. Even though Coral Reefs become bleached and change color, they can still be revived if we take the necessary precautions to stop polluting their environment. If we don’t make these changes soon, the Coral Reefs could be lost forever.


Sierra Club – “Is Your Sunscreen Destroying Coral Reefs?

Safe Sunscreen Council

Environmental Working Group – “The Trouble in Ingredients in Sunscreens

ColoreScience – “Zinc Oxide Sunscreen VS. Titanium Dioxide Sunscreen