What’s it all about?

• The term ‘reef safe’ positions itself alongside coral bleaching, which incorrectly implies that chemicals are the cause of the bleaching
• Coral bleaching can be caused by a number of factors, however rising ocean temperature is the most likely
• Whilst some sunscreen chemicals have been associated with coral bleaching, the link is tenuous, regardless of this it clearly it’s preferable to minimise the contamination of beaches and waterways

What is reef safety?

Reef safety is a term used to broadly suggest a product, particularly a sunscreen, is safe for use at beaches and other areas surrounding coral reefs. These claims are based on the questionable belief that some sunscreen active ingredients cause coral bleaching. We say it is questionable as it is associated with observations of coral bleaching in reef areas and the perceived correlation between human activity, sunscreen chemicals in the waterways and the bleaching of coral.

The term “reef safe” has no firm definition and is not regulated by any independent, impartial authority, instead, it is a concept that many brands use at an increasing frequency to differentiate their product in a competitive market.

Coral bleaching

Coral bleaching occurs when the coral expels the symbiotic algae that lives within the coral tissue, this algae is responsible for the colouration (zooxanthellae) that’s associated with healthy coral. The algae is expelled as a result of an external stressor in the form of changes in the surrounding environment, including nutrients in the water, light and temperature (but also reportedly associated with sunscreen chemicals).

Coral that has become “bleached” is at risk of dying, yet when the external stressor is not severe or prolonged in nature, the symbiotic algae can return and the coral recovers. In contrast, when the stress is severe and prolonged, the coral which has now become exposed to the stress that the algae had protected it from can then die.

There is evidence of coral bleaching globally, which is a major environmental concern. However, it must be noted that the actual cause is not well understood and is an area of active research.

The term ‘coral bleaching’ can be harshly interpreted. We immediately associate ‘bleaching’ with chemicals used around the home and ‘bleach’ as the adopted term for any chemical that causes whitening. It is for this reason that coral bleach is better referred to as ‘coral decolorisation’ to remove the stigma that inevitably accompanies the word ‘bleach’ because of the understanding that chemicals are not the most likely cause of damage.

Sunscreens have been associated with contributing to coral bleaching, however it is important to understand that coral reefs are threatened by an ever-increasing number of sources. These include climate change and increased ocean temperatures, along with marine-based diseases, coastal development and an array of chemical contaminants from agriculture and other sources.

Why increasing ocean temperatures are the most likely cause

During the 20th century water temperatures increased at a rate of 0.08degC every 10 years on average, however average temperatures in shallow coastal regions (where reefs are typical) are likely higher due the effects of sun exposure on the water, changing tides and the associated water depths.

The Great Barrier Reef has been impacted by several bleaching events, most recently in the years 2016, 2017 and 2020. Unlike the beaches of Hawaii, parts of the Great Barrier Reef aren’t exposed to considerable amounts of human activity and are incredibly remote, so to draw a correlation between sunscreen and coral bleaching of this reef is quite the reach.

A report by the Intergovernmental Panel on Climate Change advised that coral reefs worldwide are projected to decline by a further 70-90% at a 1.5°C increase in temperature, with greater losses at a 2.0°C increase. Based on the above 0.08degC increases, this means that the 70-90% decline will occur in ~190 years from now and the greater (and presumably final) losses in ~250 years.

Why sunscreen is in the firing line

Sunscreens have been linked to coral bleaching, in part, by the unsurprising detection of sunscreen ingredients around swimming beaches and the observation of coral bleaching events in the surrounding reef areas.

The highest rates of detection are in densely populated regions, particularly areas with high levels of tourism in tropical locations where coral reefs are common (Hawaii, Fiji, Australia, Indonesia, the Caribbean etc). Despite measurable amounts of sunscreen chemicals detected in the water surrounding beaches, this does not mean that sunscreens are the cause, this is an example of a spurious correlation – where variables appear to be causal but are not.

The concentrations of sunscreen chemicals detected in sea water vary significantly, however overall, the dosages are incredibly low and in the order of parts per trillion (ng L-1).

The detection of sunscreen chemicals in beaches triggered an entrepreneurial US-based environmental laboratory to undertake experimental research that aimed to directly link a sunscreen active to coral bleaching.

This environmental laboratory then published a questionable research paper indicating that Oxybenzone (Benzophenone-3), contributed to coral bleaching. This finding doesn’t appear to have been replicated by other research laboratories and has been contradicted entirely by others including a study in Bermuda by the Bermuda Institute of Ocean Sciences in partnership with Scripps Institution of Oceanography – University of California.

The environmental laboratories research does not appear to have been repeated for other purportedly “non reef safe” sunscreen ingredients like Octinoxate (Octyl Methoxycinnamate) or Octocrylene for example, yet the laboratory suggests on their website a wide array of sunscreen actives are harmful, despite not having been tested in the same manner as Oxybenzone, and that other untested actives are miraculously safe.

This environmental laboratory now acts as an authority and certifier for brands to include an “environmental and reef safety certification”. This is granted on the basis of a sunscreen being absent of sunscreen chemicals that have not been tested and is simply a half-baked paper-based safety assessment. Had the individual sunscreens been tested for their impact on reefs (or associated algae) in-vivo, incorporating other formulations ingredients that may promote penetration of potentially toxic compounds that increases risk, then and only then, would such a certification truly have merit.

The questionable ‘not reef safe’ list

The same American environmental testing laboratory has published a list of all supposedly ‘unsafe ingredients. 

Below is a consolidated list of all sunscreen actives available globally, some of which are apparently ‘unsafe’ according to the testing laboratory and compares this finding with the European Chemicals Agency (ECHA) aquatic hazard classification. The ECHA manages the technical and administrative aspects of the implementation of the European Union regulations.

Learn more about the environment and water safety via the blog ocean safety and sunscreen ingredients.