Busting the myth that sunscreen affects coral reefs

Oxybenzone (Benzophenone-3) and coral reefs – separating facts from fiction

Fact 1: the study that claimed sunscreen is 'killing reefs' was done in a small dish in Israel.

Fact 2: sunscreen floats on top of water - reefs are on the bottom of the ocean.

We’re bombarded with messages about what some people say are harmful toxins in household cleaning products, beauty and skin care products - also more recently, sunscreens.

One ingredient in sunscreens that gets a bad rap is Oxybenzone (Benzophenone 3). Some people claim that Oxybenzone is damaging to our reefs.

True? Here we examine this claim. And as usual, we look to science and research for the facts.* **

The importance of sunscreen

We wear sunscreen to try and prevent getting skin cancer, a disease that each year kills around 2000 Australians. That figure has been widely reported but it's not so well known that on each working day in Australia there are 2500 treatments, including excisions, for preventable skin cancers. The human cost is tremendous.

No one should be discouraged from using approved sunscreens without multiple, supporting scientific studies.

It’s worth noting that the chemicals used in sunscreens are approved universally. These regulatory decisions are based on sound scientific evidence based on multiple studies; they’re not based on internet conjecture

Also, it’s important to remember that sun damage is the most prevalent cause of ageing of the skin, so sun protection is imperative in the prevention of both skin cancers and premature skin ageing.

“No-one should be discouraged from using approved sunscreens without multiple, supporting scientific studies.”

Where did the ‘reef safety’ concerns come from?

Based solely on one study, there seems to be concern around using sunscreens when swimming near coral reefs, because they ‘threaten the existence of coral reefs’. The study was done on one compound only, Oxybenzone (BP-3, Benzophenone 3).

This study does not prove Oxybenzone kills coral

The published research stated:

LC50 8hrs of Oxybenzone is 3100 parts per billion (ppb), and when exposed to UV light. (LC50 8hrs means 50% of the coral planulae will die after 8 hours at this concentration, and when exposed to UV.)

Measurements were conducted at several popular swimming sites in the tourist areas of Hawaii, and the U.S. Virgin Islands. At one of the most popular beaches on Maui, with more than 500 swimmers per day, the Oxybenzone levels were well below the quantitative measuring range. i.e the measuring equipment was barely able to detect levels. It measured 8 ppb and another beach measured at 19.2ppb - Remember, the LC50 level for coral is 3100ppb.

The ‘worst’ case found by scientists was in Trunk Bay in the U.S. Virgin Islands that has 2000 visitors per day. With its significant swimmer density in such a small area, the Oxybenzone levels were under half the study’s published LC50 levels. The levels were 1395ppb at 35cm deep and 95ppb at the edge.

It should be noted that the measurements were taken where the greatest concentrations of sunscreen would be. No measurements were taken at a depth of 2 to 3 metres where most coral lies.

“Sunscreen agents cannot possibly stay suspended in sea water or come into contact with growing coral for any length of time.”

Sunscreening agents are held within a sunscreen emulsion. These have a density lower than water so they float to the top of the water and are carried away by currents. Ever noticed a small sunscreen slick on top of swimming pool water? This demonstrates exactly where the sunscreen is – it’s not distributed evenly from top to bottom in the pool. Sunscreen agents cannot possibly stay suspended in sea water or come into contact with growing coral for any length of time. 

Why this study is unreliable at best

The study that warns of dangers of Oxybenzone to coral was conducted by The Inter-University Institute of Marine Sciences in Israel, on coral planuale (baby coral).

The study results are inconclusive, unreliable and inaccurate as these were the conditions:

  • Artificial seawater was used.
  • PTFE-Teflon microplates were used.
  • Oxybenzone is a solid that doesn’t melt until it’s heated to 62 degrees, so by itself, it’s simply not soluble in seawater, so it first had to be first dissolved in dimethyl sulfoxide.
  • The researchers appear to have allowed for the toxic effects of the dimethyl sulfoxide on the coral planulae.
  • No other factors appear to have been considered in the studies eg. sea temperature fluctuations, diesel pollutants from the underwater exhausts of tourist boats, carbon monoxide and solubilised oils from private boat exhausts, human urine content in popular swimming areas, toilet water discharge from boats.

Scientists disagree with reef/sunscreen study

"Little evidence links sunscreen to coral-reef damage', say scientists Carys Mitchelmore and Doug Fenner, in a scathing opinion piece.

"People are being led to believe there is extensive scientific evidence about the impact of oxybenzone on corals, and this is simply not true."

Is sunscreen a scapegoat for coral decline? is discussed in a recent paper in the journal of Environmental Toxicology and Chemistry (ET&C),

Carys Mitchelmore is a professor in environmental science/aquatic toxicology at the University of Maryland Center for Environmental Science, Chesapeake Biological Laborator. Doug Fenner is a coral reef monitoring ecologist who has extensively studied reefs in Hawaii, the Caribbean, the Philippines, Australia and Samoa.

What about Australia and our beautiful reefs?

CSIRO, Australia's peak scientific body, agrees there is no link between sunscreen and reef damage. It reviewed studies on the health of one of Australia's most famous reefs, the World Heritage Listed, Ningaloo Reef. They found despite significantly increased tourists numbers swimming around this reef, it was in better health than 30 years ago. 

Australia actively refuses to ban sunscreens, along with the USA mainland and every European country. This, as opposed to bans in a tiny number of places gives even greater credence to the belief that:

“No-one should be discouraged from using approved sunscreens without multiple, supporting scientific studies.”

Ningaloo Reef is a heavily visited reef off the West Australian coast — it’s the largest fringing reef in Australia. It has escaped any recent coral bleaching and some areas are in the same condition as 30 years ago. If sunscreens were, in reality, affecting coral reefs, such a heavily visited tourist hot-spot would be the first to show the signs.

In May 2016, CSIRO ecologist Damian Thomson said that a major study of Ningaloo Reef had found that Ningaloo was unaffected by the current bleaching 'event' that has hit Queensland’s Great Barrier Reef and other reefs off WA’s northern coast. The CSIRO ecologist said, “It’s a relatively small tract of reef when you look at the extent of the Australian coastline, but for the number of people that love holidaying there or going there for other activities, it is very well used.”

CSIRO research surveyed 70 sites at Ningaloo and found no coral bleached at locations where bleaching was recorded in 2010. At Osprey, on the western part of Ningaloo, results were as good as those taken in 1987.

There is currently no study that says the Great Barrier Reef is affected by sunscreens such as Oxybenzone.

Our reefs are mostly in open water. We don’t have numerous small inlets, with hundreds of swimmers, where concentrations of substances might build up on the surface from lack of current flow.

Coral is being bleached, as a natural event, in areas far from human habitation as a result of natural cycles. In remote areas significant bleaching events occur after heavy rainfall resulting in fresh water run-off from coastal rivers. Most often, the coral recovers without intervention.

Bottom line

The assumptions from the aforementioned study that Oxybenzone ‘"threatens the existence of coral reefs" simply cannot be substantiated by the results or the methodology.

The threat of skin cancer however is very real. Because of this, Simplicité promotes the use of sunscreen for the protection of the skin at all times when outdoors.

*Information and opinions expressed in this post are based on the expertise, knowledge and research from Simplicité co-founder David Lyons, Naturopath and Herbalist.

**Quoting various data from: Toxicopathological Effects of the Sunscreen UV Filter, Oxybenzone (Benzophenone-3), on Coral Planulae and Cultured Primary Cells and Its Environmental Contamination in Hawaii and the U.S. Virgin Islands.
by Downs CA1, Kramarsky-Winter E, Segal R, Fauth J, Knutson S, Bronstein O, Ciner FR, Jeger R, Lichtenfeld Y, Woodley CM, Pennington P, Cadenas K, Kushmaro A, Loya Y.


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David and Robin Lyons

Simplicité Founders

"We help our customers to never again feel disappointed or worried about their skin. Every day we hear from surprised, happy, satisfied people about the most effective skin care products they’ve ever found."