Photo by Nora Tropicals / Unsplash
It is rare for most governments to proactively protect living systems. It’s so infrequent, in fact, that any instance should be cause for celebration. So, when Hawai’i, Florida, the U.S. Virgin Islands, Palau, and several island nations banned certain sunblock ingredients believed to harm coral reefs, we put the champagne on ice.
But when these bans got ahead of the issue, did they also get ahead of the science? Some researchers are asking if the banned substances – clearly harmful to coral in high concentrations in the lab – are actually damaging coral in the wild; while others, more importantly, question whether their replacements are, in fact, coral safe.
Corals and other marine dwellers are already crushed by so many pressures – heat, acidity, fishing, invasive species, coastal construction, shipping, and sewage pollution among others – that adding sunblock to the list is simply piling on. But somewhere between 6,000 and 14,000 tons of the stuff is estimated to be released into coral reef waters annually, so understanding the impact of UV screens is critical.
Snorkelers, Blue Lagoon, Indonesia, in 2019. Photo by Taylor Simpson / Unsplash
Indeed, with coral tourism generating around $36B in local revenue and producing some $375 billion in commerce overall, further coral degradation is an enormous threat. Clearly, action must be taken, and the local authorities listed above have taken it by banning several so-called organic – chemical – UV blockers.
The Parks Service, for example, says flatly that “sunscreens that include the ingredients oxybenzone, octinoxate, and avobenzone, which absorb UV rays, can harm coral reefs, leading to coral bleaching and adverse effects of reef reproduction.” There is some strong laboratory evidence for this claim, and tests have found these substances in reef waters and in the tissues of some marine animals.
But the Service and others are going farther, actively steering bathers to ‘inorganic,’ mineral-based sunscreens, notably zinc oxide (Zn0) and titanium dioxide (Ti02), nano-sized metal particles that physically block, rather than absorb, harmful light, and that are believed to be benign for coral. Dozens of sunscreens are now being marketed as ‘reef safe’ and ‘coral friendly’ leading one 2020 Marine Policy white paper to urge the creation of “clear and consistent ‘reef safe’ labeling standards,” which, it says, would “enable individuals to make more informed sunscreen purchasing decisions.”
Bleached Acropora coral colony in the Andaman Islands, Indian Ocean. Photo by Vardhanjp.
Source Wikimedia Commons
But are there ‘more informed’ decisions to be made? Is it known if these mineral-based UV blockers truly coral safe? Or that the chemicals listed above actually harm reefs in situ? “The science about the possible threat that sunscreen poses to the environment,” Consumer Reports asserted this August, “is far from settled.”
Apparently, the National Academies agrees and has called on the U.S. Environmental Protection Agency (EPA) to conduct a thorough risk assessment of all commercial UV-blocking ingredients, encompassing dangers to both human and marine life. In the Academy’s words, “the risk assessment should cover a broad range of species and biological effects and could consider potential interacting effects among UV filters and with other environmental stresses such as climate change.”
The supposedly coral-friendly components, Ti02 and Zn0, “are often considered ‘reef safe’ despite limited information on the toxicological effects of these compounds in corals,” according to the author of a recent study.
Man with black (Ultraviolet-A) light. Image by Klaus Hausmann / Pixabay
Ti02 appears to more-readily block the UV-A rays associated with aging skin, while zinc oxide Zn0 handles UV-Bs, which burn exposed dermal tissue. Together, they create a formidable screen for human skin and, when applied as indicated, adequately protect the skin from harmful radiation.
But on coral, there is substantial laboratory evidence indicating that high concentrations of these metals are harmful, even fatal to corals, promoting expulsion of critical symbiotic algae, tissue mortality, and more. However, points out Consumer Reports, “the levels of those chemicals in the water, on average, are still quite a bit lower than those reported in the majority of studies to be toxic to marine life.”
In fact, it is difficult to measure mineral UV blocker toxicity in wild aquatic environments “in part because these minerals occur naturally and, in nano form, are currently impossible to distinguish from commercial particles in sunscreen.”
Vietnamese nón lá rice-straw hats in Ho Chi Minh City, Vietnam.
Photo by Dan Kempner. Source: Wikipedia
In other words, we don’t truly know, as yet, whether any of the commercially available sun-blockers, labeled ‘reef-safe’ or not, actually merit that title.
Yet the whole argument could, with the cooperation of the public, be rendered moot. Since at least the bronze age, humans have employed simple sun-blocking methods requiring neither nano minerals nor chemicals.
Japanese women with parasols. Japanese woodblock print. Source: Wikimedia Commons
Parasols, for one: brilliantly effective and still popular as sunshades in many parts of the world, parasols go back some 3,000 years. Wide-brimmed hats, keffiyeh-style scarves, along with sunglasses, gloves, and other photoprotective gear, offer excellent UV shielding on land. In the water, if the maximum-exposure trend of Speedos and bikinis once gave way to the more sedate styles of the past, bathers could receive maximum UV blocking with no impact on coral. Sleeves, rash guards, and wetsuits keep the sun away and never wash off.
We don’t truly know which, if any, commercial sunscreens are coral safe. Neither, it seems, do the governments banning some, and the companies promoting others as benign.
Surfers wearing ‘rash guards’ or ‘rashies’ on Punta Carnero beach, Ecuador.
Photo author: Mathias Poujol-Rost. Source: Wikimedia Commons
While it’s terrific that, for once at least, actions are being taken to protect the delicate coral before there is a massive public outcry, that is not enough. We need to know such things are safe before we promote them. In the meanwhile, a return to simpler methods that can be worn or held, and that don’t rely on dubious creams and sprays, seems prudent. And the sooner that risk assessment is undertaken and completed, the better. The race has a responsibility to protect human skin, but also the last surviving coral reefs.
 There are many language- and location-dependent spellings for this garment
 It should be noted that the synthetic microfibers comprising many of these garments, as we explained in Nano Air: The Plastic River is Not Wet, have environmental issues of their own, including coral degradation. There is significant evidence that corals are ingesting them in significant quantities that serious harm is done thereby, from “host–symbiont relationship [bleaching], photosynthetic efficiency, tissue necrosis, calcification rates, energy demand, reproductive success and overall fitness,” and more. However, the majority of micro-and nano plastic (MNP) reaches the ocean from either microplastic degradation, from the washing-and-drying process, or from the air, rather than from actually wearing such garments while swimming.