Image copyright Getty Images Image caption Hawaii's tourism industry sees over eight million visitors each year - adverse effects from sunscreen chemicals can add up

Hawaii has become the first US state to pass a bill banning the sale of any sunscreens that have chemicals known to harm coral reefs.

The bill bars the sale of sunscreens containing chemicals oxybenzone and octinoxate, which some scientists say contribute to coral bleaching.

The chemicals are used in over 3,500 of the most popular sunscreen products.

The bill, which would take effect in 2021, now awaits the signature of Democratic Governor David Ige.

Democratic Senator Mike Gabbard introduced the bill, which proposes to end the sale of any non-prescription sunscreens containing oxybenzone and octinoxate, statewide.

Mr Gabbard told the Honolulu Star Advertiser that if the governor signs the bill, it would become "a first-in-the-world law".

"Hawaii is definitely on the cutting edge by banning these dangerous chemicals in sunscreens," Mr Gabbard said.

"This will make a huge difference in protecting our coral reefs, marine life, and human health."

The bill states that the chemicals kill developing coral, increase coral bleaching and cause "genetic damage to coral and other marine organisms".

Image caption Banks of coral off the coast of Oahu, Hawaii

What do scientists say?

Craig Downs, one of the co-authors of the main study showing the adverse effects of oxybenzone and octinoxate on reefs, told the Washington Post in 2015 that "any small effort to reduce oxybenzone pollution could mean that a coral reef survives a long, hot summer, or that a degraded area recovers".

The scholarly journal Nature noted that other reef scientists were unsure that banning sunscreens would have a big impact.

"Banning sunscreen will not solve other problems: for example, temperature anomalies, overfishing, coral predators and the big issue of coastal runoffs that pollute and destroy reefs," Jorg Wiedenmann, head of the Coral Reef Laboratory at the University of Southampton in the UK told Nature.

"But if you have places with a high load of tourists going in, it is not unreasonable to stay cautious and say, 'Yes, there may be additive effects.'"

Hawaii's waters see more than eight million tourists each year, and the visitor numbers have been increasing.

Mr Downs' study, published in the Archives of Environmental Contamination and Toxicology journal, found that an estimated 12,000 metric tonnes of sunscreen end up washing into coral reefs.

The Office of Hawaiian Affairs, a public agency advocating for Native Hawaiians, has supported the bill, along with a number of environmental nonprofits.

Only four Republican representatives opposed the bill in the House, but several local associations and companies have also spoken out against it.

The Star Advertiser reported that Bayer, the company that manufactures Coppertone sunscreen, said there are no similar ingredients available in the US with the same effectiveness as oxybenzone.

The Hawaii Medical Association told the newspaper that it disagreed with the bill due to a lack of peer-reviewed evidence suggesting that sunscreen caused coral bleaching, while plenty of evidence shows that sunscreen protects from skin cancer.

Media playback is unsupported on your device Media caption Sounds from the Great Barrier Reef have got quieter over the past five years

The governor has not indicated whether he will sign the bill.

"The world was watching. We delivered," wrote Senator Will Espero on Twitter, when the senate passed the bill.