"It is estimated that up to 6,000 tons of sunscreen is released annually by tourists in reef areas, and because sunscreens are often petroleum based, they don’t biodegrade.
When chemicals in sunscreen come in contact with reefs, the coral becomes stressed, pushing out the algae living inside and leaving behind a vulnerable skeletal structure. As coral reefs lose their biological inhabitants due to toxins, pollution and increased temperatures due to global warming, they also lose their pigments, becoming “ bleached.”
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Well how do we know which sunscreen to buy?? The article says look for sunscreens that are free of petrochemical active ingredients and nanoparticles as these are also harmful to humans. It is said that old fashioned zinc-oxide is as safe as ever!