Are Sunscreens Destroying the Earth's Coral Reefs?

by Dr. Diana Howard

If it feels like a case of déjà vu you are right! Once again we are dealing concerns about the use of sunscreens and health of coral reefs on our planet. About 6 years ago an article first appeared in National Geographic Magazine stating sunscreens were causing coral reefs to die.

As you might expect this study caused an enormous outcry from the public and environmental groups all claiming sunscreens were environmental hazards. What is the basis for this claim? A little background on coral reefs is needed to understand the issue. Basically, coral reefs are made by tiny animals called coral polyps. The polyps can only survive with the help of single-celled algae called Zooxanthellae. Believe it or not it is the algae that gives coral its beautiful color! Unfortunately, when the sea temperature rises above a critical level, the Zooxanthellae die and the coral turns white (hence the term ‘bleaching'). Just before they die the Zooxanthellae turn a more intense fluorescent color. Anyone who snorkels or scuba dives has seen this brilliant fluorescing coral, which is actually dying coral.

So what was the basis of this scare mongering tactic? Dr. Robert Danovaro at the Polytechnic University of the Marche in Anacona, Italy (Environmental Health Perspective vol 116, April 2008) published a study that stated, "4-6,000 metric tons of sunscreen wash off swimmers per year globally." He calculated that "10% of coral reefs are in danger" and stated "chemical sunscreens should be avoided in favor of physical sunscreens." He did however note that, "sunscreens are not the only factor behind declining reefs". As you might expect the media chose to overlook this latter point and instead scare the public into not wearing sunscreens. Likewise, some clever marketers decided to brand coral reef safe sunscreens which use zinc oxide and titanium dioxide instead of chemical sunscreens. Of course it would only be a matter of time before someone complained that these physical sunscreens were not biodegradable and also detrimental for the earth. But let's go back to the original "claim."

In response to Dr. Danovaro's, claim several expert authorities on coral reefs came out to oppose his findings. Prof. Hoegh-Goldberg, Biological & Chemical Sciences at University Queensland stated, "This study is stretching the findings and conclusions to ridiculous extremes." In addition, Durwood Dugger, University Florida, and founder of Biocepts Aquaculture commented that, "the authors conclusions are neither valid nor supported scientifically; you must consider the dilution factor in the ocean. There is no sampling of ocean waters around reefs to determine if sunscreens are even present and no one has ever detected sunscreens in the ocean. Furthermore, they have not excluded other environmental contributing factors. It is an accepted fact that "during the past 20 years, coral bleaching has increased dramatically. Some possible causes include temperature change, excess UV radiation, pollution, bacterial pathogens, pesticides, hydrocarbons, other contaminants."

"Any contaminant can experimentally damage a coral under artificially high concentrations. The amount [in the wild] must be tiny due to dilution," commented Terry Hughes, director of the Australian Research Council's Centre of Excellence for Coral Reef Studies at James Cook University in Queensland. "Imagine how much water a tourist wearing one teaspoon of sunscreen swims through in an hour-long snorkel. Compared to real threats like global warming, runoff and overfishing, any impact of sunscreen is unproven and undoubtedly trivial," he said.

Ove Hoegh-Guldberg, director of marine studies at the University of Queensland in Brisbane, said the study is interesting, but notes that many factors are likely to be responsible. "Bleaching is like a runny nose: there are lots of things that could cause it. Climate related bleaching is a direct consequence of heat stress and does not involve viruses or bacteria."

As you can see the claim that sunscreens are destroying our coral reefs is not well supported by many authorities in the scientific world and it would be premature and quite frankly dangerous for individuals to STOP wearing sunscreen while at the beach or swimming until such time that this claim can be fully supported with scientific facts. Unfortunately, many journals and papers have reignited interest in this story as we enter into summer season and we are already getting questions from consumers about the safety of sunscreens and the coral reefs. It is my expert opinion, as well as that of many other scientists around the world, that until additional studies are done to confirm or substantiate the 2008 study there should be no concern that sunscreens are harming the environment. So go to the beach, have a great time and wear your sunscreen!

References:

1. Environmental Health Perspective vol 116, April 2008

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Are Sunscreens Destroying the Earth's Coral Reefs?