Check out this answer from Consensus:
The evidence is clear: certain sunscreen ingredients are harmful to coral reefs, including the Great Barrier Reef. While sunscreens play a crucial role in protecting human health, it is essential to balance this with the need to preserve marine ecosystems. By choosing eco-friendly sunscreens and supporting regulations that limit the use of harmful chemicals, we can help protect the Great Barrier Reef for future generations.
The Great Barrier Reef, one of the most biodiverse ecosystems on the planet, is facing numerous threats, including climate change, pollution, and overfishing. Recently, the impact of sunscreen on coral reefs has garnered significant attention. This article explores the evidence linking sunscreen use to coral reef damage, particularly focusing on the Great Barrier Reef.
The Role of Sunscreen in Coral Bleaching
Sunscreens contain various organic and inorganic UV filters to protect human skin from harmful ultraviolet radiation. However, these chemicals can have detrimental effects on marine life, particularly corals. Studies have shown that certain sunscreen ingredients can cause coral bleaching, a phenomenon where corals expel the symbiotic algae living in their tissues, leading to a loss of color and vital energy sources.
Inorganic UV Filters
Inorganic filters like zinc oxide (ZnO) and titanium dioxide (TiO2) are commonly used in sunscreens. Research indicates that uncoated ZnO nanoparticles can induce severe and rapid coral bleaching by disrupting the symbiosis between corals and their zooxanthellae, the algae that provide them with energy through photosynthesis. Conversely, modified forms of TiO2, such as Eusolex® T2000 and Optisol™, have shown minimal impact on coral health, suggesting they are more eco-compatible1.
Organic UV Filters
Organic UV filters, including oxybenzone (benzophenone-3), octocrylene, and octinoxate, have been identified as significant contributors to coral bleaching. These chemicals can induce viral infections in symbiotic algae, leading to the lytic viral cycle and subsequent coral bleaching. Even at low concentrations, these substances can cause rapid and complete bleaching of hard corals3 4.
Environmental Contamination and Impact
The widespread use of sunscreens has led to the contamination of marine environments. Studies have detected UV filters in almost all water sources globally, and these chemicals are not easily removed by wastewater treatment processes. In areas with high tourist activity, such as the Great Barrier Reef, the concentration of these harmful substances can far exceed levels known to be detrimental to corals4 5.
Case Studies and Observations
In Hawaii and the U.S. Virgin Islands, significant levels of oxybenzone have been found in coral reef areas, with concentrations ranging from 0.8 to 1.4 mg/L. These levels are sufficient to cause deformities and bleaching in coral planulae, the larval form of corals. Oxybenzone has also been shown to be a genotoxicant, causing DNA damage and skeletal endocrine disruption in corals7.
Mitigation and Alternatives
To mitigate the impact of sunscreens on coral reefs, some regions have implemented bans on harmful UV filters. Hawaii, for example, has prohibited the sale of sunscreens containing oxybenzone and octinoxate. Additionally, promoting the use of mineral sunscreens with eco-friendly formulations, such as those containing non-nano ZnO and TiO2, can help reduce the environmental footprint of sunscreen products5 9.
Is sunscreen damaging the Great Barrier Reef?
Douglas Fenner has answered Uncertain
An expert from National Oceanic and Atmospheric Administration in Marine Biology
An initial study (by Downs) found that sunscreen chemicals can damage coral larvae in aquaria in a lab. Larvae may well be more sensitive than adult corals. The problem is that in order to know what the effects are of corals on reefs, you have to also know what the concentrations are in the water where they live. If the concentrations are above those that cause damage, they are likely damaged, if they are below concentrations that cause damage they are unlikely to be damaged. A recent study of European sunscreen ingredients (which are different from US ingredients) found no effects up to the maximum of concentrations that can be dissolved in water, except for zinc, which was harmful. They used adult corals. A review of studies so far found no strong evidence of damage to corals. But it is not yet very well studied, experimental designs have not been the best, and particularly there hasn’t been widespread testing of reef waters.
It is good to remember that people who use sunscreen do not want it to wash off in water, so the manufacturers commonly say on the packages that it resists washing off. They try to make it insoluble, so it generally has low solubility.
So far as I know, there is no hard evidence of even a single coral being killed in the wild by sunscreen, though there are probably some enclosed bays with lots of tourists where they may be impacted. In comparison, things like mass coral bleaching, crown of thorns starfish, diseases and cyclones (=hurricanes=typhoons) have killed billions, maybe even trillions of coral colonies in recent decades (though still well less that half of all the world’s corals, and in many but not all places, the corals have largely recovered. The outstanding exception being the Caribbean, where they have not recovered).
As for the Great Barrier Reef, people who have not been out on that reef may forget just how gigantic it is, and how much of it is far offshore, and how tiny the areas where people dive are compared to the whole reef. It appears near impossible that most of that reef system could have damage from sunscreen. It should be remembered that there may well be sunscreen in sewage from people showering after being out in the sun. But all of Australia’s large cities are way south of the Great Barrier Reef, and the best corals are far, far off shore, 70 miles offshore from Townsville and 35 miles off from Cairns. North of Cairns, human populations quickly dwindle and the northern Great Barrier Reef has essentially NO people on land nearby, and essentially NO divers or snorkelers or sunbathers.
Sunscreen danger has been hyped more than the scientific evidence supports, at this point. It does have potential for damage, but the areas with large numbers of people in the water, in small, enclosed bodies of water with corals, are small and very few in number (Hanauma Bay on Oahu, Hawaii comes to mind). And coral reefs other than such places are the vast, vast majority of coral reef area in the world. And there are vastly more dangerous things to coral than sunscreen. One study that rated risks for extinction of coral species rated the risk from sunscreen as “negligable.”
Downs original study has been criticized for weak methods. I suggest looking critically at his most recent review, and looking at papers he uses to support his contention that sunscreens kill corals, to see how strong they support his contention. He used to have a statement on his website, in which he quotes a journalist who wrote something like ‘sunscreens are the most damaging of all things humans do to corals, including mass coral bleaching.’ Which is patently false. Downs’ supporters told me he knows that is not true. He may have removed it from his website (I haven’t checked recently), but it is possible his belief goes beyond what the scientific evidence supports.
Hopefully, stronger studies will come out in the near future. Several decades ago, there were people who had discovered that corals make and contain chemicals that absorb ultraviolet rays, called “MAAs” “Microsporine-like amino acids.” They are non-toxic and absorb UV well. There was a project to try to use them in sunscreen. But for some reason it never seems to have been commerciallized. I don’t know why.
Fel, J-P., Lacherez, C., Bensetra, A., Mezzache, S., Béraud, E., Léonard, M., Allemand,
D., and Ferrier-Pagès, C. 2018. Photochemical response of the scleractinian coral
Stylophora pistillata to some sunscreen ingredients. Coral Reefs 38: 109.
Mitchelmore, C. L.., Burns, E. E., Conway, A., Heyes, A., and Davies, I. E. 2021. A
critical review of organic ultraviolet filter exposure, hazard, and risk to corals.
Environmental Toxicology and Chemistry 47: 967-988.
Downs, C. A., Cruz, O. T. and Remengesau, T. E. Jr. 2022. Sunscreen pollution and
tourism governance: Science and innovation are necessary for biodiversity
conservation and sustainable tourism. Aquatic Conservation: Marine and
Freshwater Ecosystems. 2022:1–11.
Is sunscreen damaging the Great Barrier Reef?
Danovaro Roberto has answered Near Certain
An expert from Polytechnic University of Marche in Marine Biology
Yes, classical sunscreen cause a serious damage to the stony corals and thus to the coral reefs. The impact is due either to the chemical filters and to the preservative used (e.g., parabens). This means that also the personal care products containing parabens are dangerous for sea life (e.g., after having a shower in a touristic location close to a reef). The impact is not simply due to the presence of toxic compounds, rather to the fact that these substances induce the viral disease of the symbiotic algae of the corals, which in turn kill the coral. The action is irreversible and lethal at minimal concentrations (a few drops can bleach 1 m2 of reef in 24 hours).