One of the coral-unfriendly chemicals in some sunblocks is oxybenzone (benzophenone-3, or BP-3).
Just one drop of it in a 50-metre swimming pool can kill or bleach coral.
Four others - benzophenone-2, or BP-2, Butylparaben, Octinoxate, 4-methylbenzylidene camphor (4MBC), also kill coral at extremely low concentrations.
The issue has rung alarm bells on social media.
One blogger asked tourists to do some research before arriving in Rarotonga and not wear sunscreen containing oxybenzone.
“Help us save our coral reefs!”
And the Ministry of Marine Resources has also raised concerns over chemicals within sunscreen that can bleach the coral.
Tourists are being asked not to wear sunblock containing oxybenzone while swimming in the lagoon.
Oxybenzone is found in an estimated 3500 sunscreen products around the world.
It acts as the sunscreen’s UV filter.
Pharmacist Shannon Saunders, the pharmacy manager at CITC says the dangers oxybenzone poses to coral reefs come from it washing off swimmers’ bodies and on to the coral.
“When it leaches off your skin into the lagoon it continues to do what a sunscreen does and coats the coral, stopping the sun from getting into it. This is not good for the coral and causes it to fold up within itself and crumble.
“We have for the past five years stocked a brand called ‘Aloe Up’ and it is completely oxybenzone-free.
“One of the difficult things is the more affordable sunscreens have these chemicals in them.
“We are trying to find cheaper sunscreens that don’t have these chemicals in them. We have ranges that are completely okay. We know they are okay and we can recommend them.”
But, she says: “It does come down to price and what consumers want to pay.
“We are trying to go ‘green’ and are working as hard as we can to get as many products in as we can. Once we have a decent range at different prices then we can cut the other ones. We did that with a particular detergent that was really harmful to the lagoon and once we found another, we got rid of it.”
Posts on Facebook say many American sunscreens contain oxybenzone, while European brands do not.
Chemicals to watch out for and avoid sunscreens that contain them are:
Oxybenzone: (Benzophenone-3, BP-3) - Sunscreen ingredient that disrupts coral reproduction, causes coral bleaching, and damages coral DNA.
Butylparaben: Preservative ingredient shown to cause coral bleaching.
Octinoxate (Ethylhexyl methoxycinnamate): Sunscreen ingredient shown to cause coral bleaching.
4-methylbenzylidene camphor (4MBC): Sunscreen ingredient shown to cause coral bleaching. Allowed in Europe and Canada, not in USA or