These active ingredients, used in more than 3500 branded creams, lotions and sprays worldwide, cause a chemical reaction that absorbs ultra-violet light, and are believed to increase the susceptibility of coral reefs to bleaching.

Some scientific studies also indicate that the chemical blockers have a toxic effect that might affect the human body’s endocrine system, which is responsible for creating hormones, or even be carcinogenic, although these findings have been disputed.

Up to 14,000 tonnes of sunscreen, most of it chemical- rather than mineral-based, are said to end up on the world’s coral reefs every year, adding another threat alongside ocean-warming, over-fishing and pollution.

Sunscreens that avoid using chemical blockers employ minerals such as zinc oxide and titanium dioxide as their active ingredients and offer a physical block to sun rays. These are also said to provide greater protection against both UVA and UVB rays.

The Hawaii Medical Association is concerned about the ban on chemical-blocking sunscreens, arguing that it could discourage sunbathers from protecting their skin and increase the incidence of skin cancers.

The law is set to come into effect in January 2021 if approved by the state’s Governor, and could inspire other coral-reef diving destinations to follow suit.

It will not affect holiday-makers bringing their own supplies with them to Hawaii, and chemical sunscreens could also be available on the islands on prescription.

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