Palau prohibits many kinds of sunscreen, threatening coral

What are the alternatives?

Not all sunscreens are "reef-toxic". But "some of the sunscreens without these chemicals are quite expensive, which is a deterrent," said Dr. Ward. "I'm sure someone will soon have it and will market these products at an affordable price."

The most common sunscreen brands on the market contain oxybenzone, said Dr. Ward. But she also warned against mineral-based sunscreens containing zinc oxide. They were once thought to be safer for coral, she said, but a recent study showed that zinc oxide could cause coral bleaching as well as microbial enrichment, resulting in training more bacteria in the water.

"I think wearing fabrics on your body is the best alternative to sunscreen," she said. "We have Stinger costumes in the summer, when it's too hot for a wet suit. Cover your entire body with Lycra – an attractive look, if you can imagine. "

She noted that reefs are threatened by major global phenomena, including global warming and ocean pollution. In comparison, she says, sunscreen is "the one we can solve."

What do others say?

Unsurprisingly, sunscreen manufacturers opposed the ban on Hawaii. But they are not the only ones to say that commercial sunscreens do more good than harm.

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

Currently, said Ms. Walker, there is no accepted standard for what constitutes an "environmentally friendly" sunscreen. "We would be worried if Australians stopped using sunscreen more generally," she said.

Kim Do, a senior industry badyst at IBIS World, a market research firm, said the new bans would encourage sunscreen manufacturers to review the ingredients used in their products, but not immediately. She said the industry "should continue to undertake product research and development activities to meet the changing consumer demand."