Australians by virtue of both a hot home climate and a relative lack of protective ozone were among the first sailors to appear at European and North American regattas wearing the original zinc oxide ‘slap’ during the 1980s… and very strange it looked too. Slap or not Blue Robinson’s (left) own experience confirms that the key word on this topic is accumulation. Respect for showing us your grumpy side
levels of 19.2 parts per billion. Opposing scientists point out that these were only a few random samples in very concentrated areas and cannot be interpolated to other reefs throughout the world. In addition, some scientists – and manufacturers of sunscreens – point out that the major cause of coral bleaching is rising ocean tempera- ture due to climate change and other envi- ronmental pollution. When coral is exposed to oxybenzone
In general, due to their insoluble and
light-reflecting characteristics, sunscreens with mineral filters are more difficult to formulate and are less cosmetically ele- gant. Micronising or nanosising the miner- als improves the ‘white cast’ but may also decrease the efficiency. Chemical filters are transparent and therefore more cosmeti- cally acceptable. Sun protection factor (SPF) only mea-
sures how well the sunscreen protects from UVB rays, but as a general rule the higher the SPF the broader the coverage becomes. UVA filtering capacity of sunscreens is
determined, regulated and measured dif- ferently in different countries. Unfortu- nately, although the SPF number may be pretty high on some sunscreens, it does not always guarantee good protection in the UVA range that is most damaging. One area of ongoing concern is the
possibility that certain chemical sunscreen ingredients, such as oxybenzone, may have estrogenic and anti-androgenic impacts on mammals, with special concern for children and pregnant women. Oxybenzone is a very small molecule
that rapidly gets absorbed into the circula- tion. It is secreted into the urine and can be detected in breast milk. In addition, it is bioaccumulated and biomagnified which leads to increasing amounts appearing throughout the marine food chain. According to the US Center of Disease
Control, approximately 97 per cent of Americans are exposed to oxybenzone. About 80 per cent of US sunscreens contain oxybenzone and there are plentiful cosmetic products that use it. Many animal studies have shown harm-
ful hormonal effects of oxybenzone; how- ever, it has been calculated that nearly 300 years of daily sunscreen application would be necessary to reach similar exposure levels
endocrine abnormalities in animal studies. 54 SEAHORSE
Importantly, oxybenzone has not been
demonstrated to accumulate in the blood. What about the coral reefs? In May
2018 Hawaii passed state legislation that sparked much debate and controversy. The legislation restricts the use of personal care products including sunscreens that contain oxybenzone and octinoxate, effec- tive from 1 January 2021. The Republic of Palau in the western
Pacific followed suit shortly afterward and the city of Key West just banned the use of the same two filters in February 2019, effec- tive from 2021. The mayor of Key West adds simply: ‘There are thousands of sun- screens out there, and we have one reef.’ These laws were prompted by several
studies showing increased amounts of active chemical sunscreen ingredients in coastal waters, with supportive evidence pointing to harmful effects of oxybenzone and octinoxate on coral reefs, a crucial component of aquatic ecosystems. Coral reefs occupy less than 0.1 per cent
of the earth’s ocean surface, yet they provide habitat for at least 25 per cent of all marine species. It is estimated that 25 per cent of sunscreen applied to the skin is washed off within 20 minutes of immer- sion, releasing approximately 14,000 tons of sunscreen into the waters surrounding coral reefs every year. Large tourist populations who frequent
Hawaii probably contribute to excess oxy- benzone and octinoxate found along the surrounding ocean shores. In addition, water-waste treatment facilities do not have effective means of filtering out these organic compounds, leading to additional contamination of coastal waters via sewage drop-off. It has further been shown that four out
to oxybenzone that caused
of five sampled sites of ocean around the Hawaiian islands displayed detectable oxybenzone levels of 100 parts per trillion. The fifth site demonstrated oxybenzone
and octinoxate it undergoes a bleaching phenomenon due to loss of membrane integrity and loss of photosynthetic pig- ments in zooxanthellae, a species of algae released from coral. Coral and zooxanthel- lae have a delicate symbiotic relationship wherein coral provides the zooxanthellae with a protective refuge and resources needed for algae photosynthesis. The algae are later consumed by the coral, providing nourishment needed for coral growth and expansion. When coral reefs are exposed to stress, such as chemical bleaching, algae dissociate from the coral, thereby disrupt- ing this relationship leading to decreased coral viability. Oxybenzone and octinox- ate were also named in other mechanisms that directly damage coral larvae DNA. Some sunscreen manufacturers responded
to the new legislation by pointing out that such a measure could compromise the health of both tourists and native Hawai- ians, as it prohibits a large portion of avail- able sunscreen products. Lots of dermatol- ogists are also worried that banning the most frequently used sunscreen ingredients allied with fake news such as ‘sunscreen is the new margarine’ will decrease the use of sunscreens and hence increase the risk of skin cancer in large populations. I am a dermatologist, a scientist, a sailor
(don’t be fooled, I didn’t write an article in Seahorse due to my sailing merits), coral reef enthusiast and care deeply about our seas. In my personal opinion, we have a choice to use proven safe sunscreen ingredients. No doubt more research is needed for
certain filters and I dare to trust the industry that they will perform the required testing that will prove or disprove current concerns and provide us with better choices. I support the American Academy of Dermatology decision to fund independent research about coral safety. I sincerely hope that ultimately we will find those sunscreens that are best for us and our environment so we can keep doing what we love: sailing. [Disclosure: Edit Harken MD, PhD is also co-founder of Harken Derm which offers a sunscreen with only mineral filters] q
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