Reef-safe sunscreens are those that do not contain chemicals that are harmful to coral reefs and other marine life. The term "reef safe" typically means that the sunscreen contains only mineral UV-blocking ingredients like oxide and titanium dioxide. Here are some key points to consider when choosing a reef-safe sunscreen:

• Active ingredients: Check the "active ingredients" label on the back of your sunscreen or personal care product to ensure that reef-harming chemicals are not included. Oxybenzone and octinoxate are two of the more widely studied chemicals in sunscreens that are harmful to reefs.

• Mineral-based: Mineral-based sunscreens that use titanium dioxide or zinc oxide to reflect the suns rays are much less likely to harm coral reefs and other marine life. The most common active ingredients in mineral sunscreens are zinc oxide and titanium dioxide.

• Particle size: Be sure to use micro-sized (or non-nano) mineral sunscreens to avoid nanoparticles, as these smaller particles can be toxic in high concentrations.

• Regulation: Unfortunately, the terms "reef friendly" and "reef safe" are not regulated, so you can't always trust products with this description. It's important to actually check the "active ingredients" label on the back of your sunscreen or personal care product to ensure that reef-harming chemicals are not included.

It's also important to note that the science about the possible threat that sunscreen poses to the environment is far from settled. However, to protect park resources and visitor safety, the National Park Service encourages the use and sale of sun protection that is less harmful to reefs, including protective clothing and mineral-based sunscreens with only titanium dioxide or zinc oxide.