Climate change, pollution and ocean-dependent industries are slowly damaging coral reefs around the world. There’s something else — something seemingly innocent — that could be contributing to the loss of these colorful underwater colonies: your sunscreen.

Some chemicals in sunscreen have been linked to damage of coral reefs, although there’s more to the evidence than what initially meets the eye. 

I don’t want to send mixed signals, so I’ll say this flat-out before diving in: You should wear sunscreen any time you are in the sun, especially if your skin is unprotected by clothes or shade. The most important thing is to protect yourself from skin cancer by avoiding UV damage, whether your method be sunscreen, clothes or umbrellas. 

Even the Journal of the American Academy of Dermatologists recognizes the potential environmental harm of certain chemical sunscreens, but reminds everyone that skin protection trumps ocean protection. 

That said, here you can learn from board-certified dermatologists and marine biologists about the pros and cons of reef-safe sunscreens, and how choosing a reef-safe sunscreen can benefit both your health and the environment’s health.

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What is reef-safe sunscreen?

A reef-safe sunscreen is a sunscreen free of chemical ingredients and small particles known to damage and potentially kill coral reefs in the oceans. Those ingredients are, to date, oxybenzone, octinoxate and octocrylene. 

Important note: These are not the same ingredients proposed by the FDA as unsafe for human use. Those chemicals are para-aminobenzoic acid and trolamine salicylate, and they are not FDA-approved for use in sunscreens in the US.

There’s more to consider than just the ingredients in your sunscreen, though, which is where things get a bit sticky: To be truly reef-safe, the particles in sunscreen must be «non-nano.» If the particle size is below 100 nanometers, coral reefs can absorb the particles from sunscreen regardless of the ingredients. 

In fact, the primary reason mineral sunscreens are more eco-friendly is due to them being non-nanotized, says Casper Ohm, a marine biologist senior research writer at Water Pollution. This means that reef-safe sunscreens «are made with bigger ‘natural-sized’ particles that are healthier for marine life and the local ecosystem,» Ohm tells CNET.  

Both nano-zinc oxide and nano-titanium dioxide can harm the aquatic environment, according to the National Oceanic and Atmospheric Association, despite the minerals’ reputations as the better alternative. 

To recap, here’s what makes a truly reef-safe sunscreen:

• No oxybenzone, octinoxate or octocrylene 
• Particle size above 100 nanometers 

Look for a «reef-safe» label when shopping, but double check the ingredients list. The phrases «reef-safe» or «reef-friendly» are not regulated by the FDA, so the simplest way to choose a non-nanotized sunscreen is to use a mineral-based cream or lotion instead of a mist or spray. Aerosolized sunscreen is almost guaranteed to contain particles smaller than 100 nanometers in size that can be ingested by coral reefs.

Here are a few popular reef-safe sunscreens to look for when shopping:

Blue Lizard Sensitive Mineral Sunscreen

Alba Botanica Very Emollient Sport Sunscreen SPF 45