Every year, many thousands of tons of sunscreen are rinsed off swimming vacationers ending up in our seas and oceans. Adding to that, our water treatment plants are not capable of fully removing the UV-filters that end up in the shower drains, causing even more sunscreen UV-filters to be released in our waters. UV-filters that have been shown to be hormone-disrupting or in various ways directly toxic to marine life, are today constantly present in our waters. Add bioaccumulation and biomagnification and we find ourselves at risk for the next big environmental catastrophe. How do you responsibly choose sunscreen and without contributing to the pollution of seas and oceans with UV-filters?
UV-Filters Cause Coral Bleaching and Kill Coral Larvae
The world's coral reefs are extremely sensitive to sunscreen pollution of the oceans. In 2008, an Italian research team showed that certain UV-filters cause coral bleaching . Corals are a type of sea animal that are entirely dependent on a symbiotic relationship with the alga Zooxanthellae. The single-celled Zooxanthellae lives protected inside the corals and produces oxygen and nutrients via photosynthesis, which also benefit the corals. It is the Zooxanthellae that gives corals their beautiful color. When stressed for various reasons, like hot weather, the corals expel their algae, giving the coral a whitish appearance, which is why this is referred to as coral bleaching. A condition that is life-threatening to the coral. Without Zooxanthellae, corals do not survive for long. The chemical UV-filters that have been shown to cause bleaching of corals are oxybenzone, ethylhexyl methoxycinnamate and 4-methylbenzylidene camphor. In addition, the preservative butyl paraben, an ingredient in many sunscreens, can cause coral bleaching as well. Oxybenzone is also directly toxic to coral larvae, which threatens the possibility for corals to re-establish after temporary heat-waves like El Niño, making the species less resilient to global warming .
Hormone-Disrupting UV-Filters Affect Fish Reproduction
Fish have also turned out to be susceptible to the effects of certain UV-filters. The hormone-disrupting effects that cause worries in man also affect fish [3-4]. They negatively affect the fishes' reproductive hormone, vitellogenin and result among other things in feminization and decreased fertility in male fish and impaired oocyte development in female fish. Studies show that the UV-filters that had the most severe effect on the reproduction in fish were benzylidene camphor and PABA, two substances that are now banned in sunscreen within the EU, but can still be found in sunscreen abroad. Another study showed that when fish were fed a mixture of three UV-filters, oxybenzone, octinoxate and a variant of PABA, it resulted in a negative evolution of fish embryos .
Bioaccumulation and Biomagnification of UV-filters Threatens Birds and Marin Mammals
Sunscreen is not the only culprit for UV-filters in our waters [6-7]. A large amount originates from various materials like plastics and textiles treated to be UV-resistant. These are made by industries a lot less limited regarding allowed chemicals compared to sunscreen production. The result is that our waters contain a veritable soup of various UV-filters that can have additive effects. That is 1+1=3. Substances can have more considerable effects and at lower doses when combined than seen in laboratory tests, where they are studied one at a time. You also have to realize that marine life is exposed during a lifetime and over generations, so it is difficult, with any degree of certainty, to predict the final consequences. Since chemical UV-filters are fat-soluble substances that accumulate in body fat, the result will be increasing levels of the substances the higher in the food chain. By that, you have to ask what the effects are on seabirds and other marine animals? The studies done so far show accumulation of UV-filters such as oxybenzone, octocrylene and 4-methylbenzylidene camphor (enzacamene) not only in fish  but also in mussels , marine birds' eggs  and dolphins  and it is possible that we are on the verge of a new environmental disaster if nothing is done about it.
Which Substances Should You Be on the Watch for in Environmentally Friendly Sunscreen?
Unfortunately, you cannot trust that a sunscreen product is not harmful to ocean life just because it says so on the bottle. There are plenty of sunscreens out there labeled "reef-friendly" that are not that friendly at all. As usual, you have to be careful and read the finely printed list of ingredients. The two worst substances to avoid is oxybenzone and ethylhexyl methoxycinnamate (octinoxate). On Hawaii, a new law was adopted last July that bans the sale of sunscreen containing these two UV-filters, oxybenzone and ethylhexyl methoxycinnamate (octinoxate). In Mexico, several tourist resorts already ban all "non-biodegradable sunscreen", meaning that only sunscreens containing solely physical UV-filters are allowed and that the sunscreens cannot contain parabens or other non-natural substances like hexyldecanol, dimethyl capramide, dimethicone, polyethylene or butylcarbamate. Moreover, the zinc oxide and titanium dioxide should be in non-nano form since the minerals are taken up by coral, fish and other sea-living organisms and nanoparticles are harmful if they reach living cells.
- Use water-proof sunscreen so that as little as possible is rinsed away into the ocean when you swim.
- Above all avoid oxybenzone (benzophenone-3) and ethylhexyl methoxycinnamate (octinoxate), but also octocrylene and 4-methylbenzylidene camphor (enzacamene). Remember also to be on the watch for PABA and 3-benzylidene camphor if you buy sunscreen outside of the EU.
- Choose instead products that contain non-nano forms of the physical UV-filters zinc oxide and titanium dioxide.
- Downs, C.A. et al., 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. Arch Environ Contam Toxicol, 2016. 70(2): 265-88.
- Danovaro, R. et al., Sunscreens cause coral bleaching by promoting viral infections. Environ Health Perspect, 2008. 116(4): 441-7.
- Ghazipura, M. et al., Exposure to benzophenone-3 and reproductive toxicity: A systematic review of human and animal studies. Reprod Toxicol, 2017. 73: 175-183.
- Fent, K. et al., UV Filters in the Aquatic Environment Induce Hormonal Effects and Affect Fertility and Reproduction in Fish. Vol. 62. 2008. 368-375.
- Li, A.J. et al., Joint Effects of Multiple UV Filters on Zebrafish Embryo Development. Environ Sci Technol, 2018. 52(16): 9460-9467.
- Ramos, S. et al., A review of organic UV-filters in wastewater treatment plants. Environ Int, 2016. 86: 24-44.
- Apel, C. et al., Environmental occurrence and hazard of organic UV stabilizers and UV filters in the sediment of European North and Baltic Seas. Chemosphere, 2018. 212: 254-261.
- Buser, H.R. et al., Occurrence of UV filters 4-methylbenzylidene camphor and octocrylene in fish from various Swiss rivers with inputs from wastewater treatment plants. Environ Sci Technol, 2006. 40(5): 1427-31.
- Bachelot, M. et al., Organic UV filter concentrations in marine mussels from French coastal regions. Sci Total Environ, 2012. 420: 273-9.
- Molins-Delgado, D. et al., A Potential New Threat to Wild Life: Presence of UV Filters in Bird Eggs from a Preserved Area. Environ Sci Technol, 2017. 51(19): 10983-10990.
- Gago-Ferrero, P. et al., First determination of UV filters in marine mammals. Octocrylene levels in Franciscana dolphins. Environ Sci Technol, 2013. 47(11): 5619-25.