This episode was originally published on August 11, 2020.

Megan Hall: Welcome to Possibly, where we take on huge problems like the future of our planet and break them down into small questions with unexpected answers. I’m Megan Hall. 

Today, we’re going to shine a light on why some scientists are worried about sunscreen.

We had Max Kozlov and Fatima Husain from our Possibly Team look into this. Welcome, Max and Fatima! 

Max Kozlov: Hi Megan! 

Fatima Husain: Hello! 

Megan Hall: So, before we talk about these concerns, will you explain how sunscreens actually work?

Max Kozlov: Well, sunscreens are designed to protect your body from ultraviolet radiation, or UV rays, that come from the sun and can cause skin cancer. 

Megan Hall: How do sunscreens protect you from UV rays?

Max Kozlov: Well, physical sunscreens sit on top of your skin and act like a shield, deflecting the ultraviolet radiation from your body.  

Fatima Husain: These sunscreens leave that classic white residue that we associate with hot beach days. They’re usually marketed as “natural sunscreens” or “mineral sunscreens.” 

Max Kozlov: But these days, many of us use chemical sunscreens, which absorb ultraviolet radiation, convert it into heat, and then release that heat from our skin.

Fatima Husain: That’s the type of sunscreen some scientists worry about most. 

Megan Hall: Why? 

Max Kozlov: Well, many chemical sunscreens are made with compounds like “oxybenzone” and “octinoxate.” And when they wash off, those ingredients might hurt marine life, and more specifically, cause something called coral bleaching.

Megan Hall: What’s that? 

Fatima Husain: If you’ve ever seen underwater pictures of coral reefs, you know that they can be all sorts of colors — green, brown, red, and sometimes even purple or blue. In most cases, these colors come from microscopic organisms that live in, and are part of, the reef itself.

Max Kozlov: Coral bleaching happens when those colorful organisms are ejected from the coral reef. 

Fatima Husain: When they’re gone, the coral reefs turn white and sometimes die. 

Megan Hall: Why is that a problem?

Fatima Husain:  Well, coral reefs aren’t just pretty objects in the water — 25% of the ocean’s fish depend on coral reefs for their habitat even though coral reefs are found in only 1% of the ocean. 

Max Kozlov: Jon Witman, who’s a marine biologist at Brown University, has been studying the same corals in the Galapagos for 20 years. He remembers when he saw them turn white.   

Jon Witman: I jumped over the side of the boat and looked down and it was like a snowstorm — they were white everywhere. It was just one of the most dramatic seascapes you can ever see. To see them diseased or white, you know, it’s concerning it really is on all levels from emotional to scientific.

Megan Hall: And chemical sunscreens can cause all this?  

Fatima Husain: Well, most scientists agree that rising sea temperatures and ocean acidification are mostly to blame, but Jon says that sunscreen chemicals can also play a role.

Max Kozlov: There is some scientific disagreement about whether there’s enough of those chemicals in the water to hurt coral reefs. 

Jon Witman: It’s not that it’s not a serious threat because it is, but for it to be harmful it requires the concentrations of sunscreen to reach pretty high levels. 

Fatima Husain: But some places that rely on corals for tourism aren’t taking any chances. 

Max Kozlov: Hawai’i, Key West, Aruba, and Palau have all banned sunscreens with those chemicals. 

Fatima Husain: That’s because those places have a lot of swimmers in relatively enclosed bays, where the concentration of sunscreen chemicals can really build up. 

Max Kozlov: Some scientists have also found that these chemicals can harm fish development, but again, it all comes down to how much sunscreen is actually in the water.

Megan Hall: So — what are my options for reef and fish-conscious sunscreen?

Fatima Husain: To find out more, we spoke with Craig Downs, a scientist who has been researching sunscreens for the past decade at the Haereticus Environmental Laboratory. Craig says there’s a pretty simple solution.

Craig Downs: Wear clothing. Wear UPF or any type of clothing. UPF is Universal Protective Factor, it’s like SPF for sunscreen, but it’s a rating for clothing. 

Max Kozlov: He says this UPF clothing provides sunscreen protection whether it’s wet or dry. 

Fatima Husain: Craig also says to look for sunscreens that are labeled “reef-safe” or “oxybenzone-free,” 

Max Kozlov: Whatever you do, it’s still important to wear some form of sun protection when you go out! 


Megan Hall: Great! Thanks, Max and Fatima! 

That’s it for today. For more information, or to ask a question about the way you recycle, use energy, or make any other choice that affects the planet, go to the public’s radio dot org slash possibly. Or subscribe to us wherever you get your podcasts. 

Possibly is a co-production of the Institute at Brown for Environment and Society and the Public’s Radio.

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