The sunscreen we slather on to protect ourselves from the sun's harmful rays is doing incredible damage to the world's coral reefs.

Researchers found that just a small amount of sunscreen containing the ingredient oxybenzone is enough to break down coral, causing it to lose its nutrients, turn ghostly white or bleach and often die. The study, published in Archives of Environmental Contamination and Toxicology, was conducted in Hawaii and the U.S. Virgin Islands, prompted by the researchers' chance encounter with a vendor who described the "long oil slick" of sunblock the hoards of tourists leave in their wake, reports the Washington Post.

According to the National Park Service, 4,000 to 6,000 tons of sunscreen enter reef areas annually. But beachgoers aren't the only ones spreading these harmful chemicals. Kids on playgrounds and runners all come home and wash off the same chemicals, and those chemicals can also end up being swept out to sea.

A coral reef and orange fish Locations that experience a lot of tourism tend to have the most coral reef damage. (Photo: Jolanta Wojcicka/Shutterstock)

Research presented at the June 2016 International Coral Reef Symposium in Hawaii studied 327 coral colonies off the coasts of Florida, Puerto Rico, and St. Thomas, St. John and St. Croix in the U.S. Virgin Islands to determine the reproductive potential of elkhorn coral, a threatened coral species that appears to be healthy.

In some locations, including the Florida Keys, the coral couldn't reproduce because it didn't have sperm or eggs. The researchers dubbed them "zombie corals," saying they were essentially walking dead and would eventually die out.

"It's pretty discouraging," said researcher John Fauth of the University of Central Florida, in a statement. "This is not good news."

However, two samples from the St. Croix area had complete reproductive ability. "Basically the places with the heaviest tourism had the most severe damage," said Fauth, who was also an investigator in the 2015 coral/sunscreen study and released another related study at the symposium. There, researchers found that oxybenzone is common in Hawaii, Florida and the U.S. Virgin Islands where concentrations peak during high tide.

"It's almost counterintuitive," said Fauth. "We think that aerosol sunscreen is to blame." That's because when you spray sunscreen, a lot of it lands on the sand or in the water. When the high tide comes in it collects all that overspray and pulls it out to sea.

The studies show that coral reefs are in more danger than we thought.

So what's the solution?

The Pacific archipelago nation of Palau was the first country to ban "reef-toxic" sunscreen. President Tommy Remengesau Jr. signed a law in October 2018 banning the sale and use of sunscreen and personal care items that contains any of 10 banned ingredients, including oxybenzone. Tourists who bring banned sunscreen to the country will have it confiscated, and businesses that sell the products will be fined up to $1,000. The law will go into effect in 2020.

One of the main reasons Remengesau signed the law was due to a 2017 study that showed sunscreen was found in the country's famous Jellyfish Lake, which was closed for a year due to dwindling numbers of jellyfish, reports the Associated Press.

While Palau is the only nation to ban certain sunscreen products so far, several other places are following suit.

In February 2019, the city of Key West voted to ban the sale of sunscreens that contain oxybenzone or octinoxate. However, the bill doesn't ban the use of it, meaning tourists could pack sunscreen bought elsewhere and still use it on the island. The city commission voted 6-1 in favor of the ban — largely because the only living coral reef in North America is located about six miles offshore from Key West.

The ban will go into effect on Jan. 1, 2021 — the same day as Hawaii's law, which uses similar language in a bill passed July 2018.

The Caribbean islands of Bonaire and Aruba voted to ban similar sunscreens, and the latest addition to this group is the U.S. Virgin Islands, which takes its ban one step further by targeting oxybenzone, octocrylene, and octinoxate, the three UV-blocking chemicals most commonly found in sunscreens, according to Mongabay. That law will go into effect in 2020.

Balancing sun safety with reef health

However, medical professionals are worried these bans could lead to higher risk of developing skin cancer and other dermatological conditions. "We want to preserve the coral reef, but ... we don't want to diminish our use of sunscreen which has been proven to reduce risk for skin cancer," Kevin Cassell, president of the Hawaii Skin Cancer Coalition, told Hawaii News Now.

If you don't want to use sunscreen containing these ingredients, what options do you have?

The National Park Service encourages visitors to take a more "reef-friendly approach" to sun protection. Although no sunscreen has been found to be completely safe for coral reefs, those with titanium oxide or zinc oxide as the active ingredients haven't been found to harm corals. NPS rangers suggest covering up with hats, sunglasses and long-sleeved shirts or rash guards. And always remember: "If it's on your skin, it's on the reef."

Editor's note: This article has been updated since it was originally published in June 2016.

Mary Jo DiLonardo writes about everything from health to parenting — and anything that helps explain why her dog does what he does.

Why your sunscreen is bad for coral reefs
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