SYDNEY >> The Western Pacific nation of Palau has become the first country to ban many kinds of sunscreen, in a move to protect its coral reefs from chemicals that scientists say cause significant damage.

Under the ban, which will take effect in 2020, “reef-toxic” sunscreen — defined as containing one of 10 prohibited chemicals, a list that could grow later — can be confiscated from tourists when they enter the country, and retailers who sell it can be fined up to $1,000.

Damage to coral reefs worldwide from climate change has been widely reported, but scientists say there is growing evidence that chemicals from sunscreen, which washes off swimmers or enters the ocean through sewer systems, also causes grave harm.

Palau passed the ban into law last week. President Tommy Remengesau called it “especially timely,” saying that a major impetus was a 2017 report that found sunscreen products to be “widespread” in Jellyfish Lake, one of the country’s UNESCO World Heritage sites.

— What threat does sunscreen pose to coral?

It has been estimated that 14,000 tons of sunscreen are deposited in the world’s oceans each year, and scientists say a number of studies have shown the product’s adverse effects on coral reefs.

Researchers found that even a low concentration of sunscreen in the water can hinder the development of young coral, said Dr. Selina Ward, a lecturer in coral reef ecology and physiology at the University of Queensland in Australia. Studies have also shown that chemicals in sunscreen can cause localized coral bleaching and can disrupt the reproduction of fish by interfering with their hormonal systems, Ward said.

Chemicals in sunscreen can be “bigger than climate change” in causing damage to reefs, Craig Downs, executive director of the Haereticus Environmental Laboratory in Virginia, said this year. In 2015, Downs led a team that found that oxybenzone, which is commonly used in sunscreen, stunts coral growth and is toxic for the algae that live within reefs, providing their color and performing other vital functions.

— Have there been other sunscreen bans?

In May, Hawaii became the first state to ban the sale of sunscreen containing oxybenzone or octinoxate, another chemical that scientists say is damaging to coral. The ban is scheduled to go into effect in January 2021.

Nonbiodegradable sunscreen is banned in some parts of Mexico. At Xel-Há, a tourist development on the Riviera Maya, visitors can swap banned sunscreen for more coral-friendly varieties and get their own back when they leave.

— What are the alternatives?

Not all sunscreens are “reef-toxic.” But “some of the sunscreens without these chemicals are quite expensive, which is a disincentive,” Ward said. “I’m sure someone will get it soon, and put out these products at an affordable rate.”

The most common commercial sunscreen brands contain oxybenzone, Ward said. But she also warned against mineral-based sunscreens containing zinc oxide. They were once considered safer for coral, she said, but a recent study found that zinc oxide can cause coral bleaching as well as microbial enrichment, causing more bacteria to form in the water.

“I think wearing fabrics on your body is the best alternative to sunscreen,” she said. “We have stinger suits in the summer, when it’s too hot for a wet suit. Cover your whole body in Lycra — an attractive look, if you can imagine.”

She noted that reefs are under threat from major, global phenomena, including global warming and pollution of the oceans. By comparison, she said, sunscreen is “the one that we can solve.”

— What do others say?

Sunscreen manufacturers, not surprisingly, opposed the Hawaii ban. But they aren’t alone in arguing that commercial sunscreens do more good than harm.

“At the moment, research on sunscreens’ effects on coral is limited,” said Heather Walker, chairwoman of the Cancer Council Australia’s National Skin Cancer Committee. “By contrast, the evidence that sunscreen prevents skin cancer is conclusive. In this context, a ban is hasty.”

Currently, Walker said, there is no accepted standard for what constitutes “environmentally friendly” sunscreen.

“We would be concerned if Australians stopped using sunscreen more generally,” she said.

Kim Do, a senior industry analyst at IBIS World, a market research company, said the new bans would cause sunscreen manufacturers to review the ingredients used in their products, though not immediately. She said the industry was “expected to continue undertaking product research and development to meet changing consumer demands.”