Qualifying as reef-safe is actually pretty simple, but the whole idea of ocean-friendly sunscreen isn’t exactly what it seems.

Did you know July is UV Safety Month? While it’s important to learn about protecting your skin and eyes from ultraviolet rays in the hot summer months, the choices we make about our own UV safety also have an impact on the environment around us. Here’s everything you need to know about making smart selections from the world of reef-safe sunscreens.

What does my sunscreen have to do with coral reefs anyway?

Research has shown that between 6,000-14,000 tons of sunscreen wash off swimmers’ bodies into the ocean every year — that’s as much as 60 million bottles of the stuff. It wouldn’t be a problem if sunscreens weren’t so dangerous, but unfortunately many of them are directly harmful to the world’s ocean ecosystems. Coral reefs are important underwater sites of biodiversity; nearly a million different species live on and around reef systems on the ocean floor.

Most sunscreen products use chemicals to prevent sun damage by dispersing UV light before the skin can absorb it. But those active chemicals are directly harmful to reefs. Don’t forget that corals are technically living animals — when coral is under stress it turns a ghostly white, which indicates it’s ill equipped to fend off disease and death. The ingredients that have been linked to coral bleaching aren’t limited to sunscreen either; many cosmetics and other beauty products pack a chemical punch and should be avoided near marine areas.

Okay, so what makes a sunscreen product reef-safe?

There are two elements of sunscreens that make them dangerous to reef life: ingredients and particle size. There’s a long list of ingredients that the most cautious reef-safe sunscreens shun, but the two major chemicals to look out for are oxybenzone and octinoxate. (Fun fact: Hawai’i was the first state to ban the sale of sunscreens made with those two chemicals!) If you want to go all the way, make sure your products also avoid: octocrylene, parabens, triclosan, para-aminobenzoic acid, and 4-methylbenzylidene camphor. 

When it comes to particle size, the rule of thumb is that bigger is better. Corals can’t filter out nanoparticles (smaller than 100 nanometers), and ingesting toxic ingredients is by definition hazardous. Micro-sized particles are acceptable, which is why most sunscreens that use the “reef-safe” label make clear “non-nano” claims on their packaging.

Well… what am I supposed to do about all this?

If you want to be completely reef-safe, consider cutting down on your ocean time or wearing a UV-blocking rash guard or wetsuit when you go in the water. Look for water resistant products that won’t wash off easily, or opt for a mineral sunscreen that blocks out UV rays with physical barriers instead of chemical ones. If you’re trusting your products to be reef-safe, make sure to double check the ingredient list and look for statements about non-nano particle size.

At the end of the day, it’s important to understand that a lot of the science behind the reef-safe conversation is still incomplete. Most of the chemical testing that has been conducted to date took place in labs at incredibly high concentrations, so it remains unclear whether sustained low-grade exposure will have the same effect on coral reefs in actual ocean environments.

Meanwhile, phrases like “reef-safe” and “reef-friendly” are not regulated by the FDA or any other agency, which means there isn’t an agreed upon standard you can assume is in place when you buy a product that carries that label.

While it’s clear that UV blockers play a role in ocean environments, so do plenty of other more pressing concerns, like global warming, for one. General consensus is that more research is required to understand the full scope of sunscreens’ impact on the long-term health of coral reefs.