How can we give a break to coral reefs this summer?

How can we give a break to coral reefs this summer?
In my lifetime, our planet has lost about half its coral reefs. From dynamite fishing to coastal pollution, predator invasions and lethal marine heat waves...these ecosystems are retreating everywhere after thriving for millions of years. Today, we know that the chemicals in our sunscreens are an additional source of pollution on popular reefs around the world. But what if something as simple as making the switch to healthy sun protection could take some pressure off the world’s most endangered ecosystems?

This year, the state of Hawaii was first in history to ban the sale of sunscreens containing oxybenzone and octinoxate to protect its coral reefs, providing countless goods and services to the people of Hawaii. This new law wasn’t received well by manufacturers, and here is why: these chemicals are used in 97% of sunscreens and 70% of cosmetics on the market as UV-filters. In other words, most personal care products seating on your bathroom shelf may contain oxybenzone (aka benzophenone-3) and/or octinoxate. So what lead Hawaii into making such a controversial ban? Since the start of my investigation I have become more and more clueless on the reasons why these compounds were approved in skincare formulations in the first place...
In case you didn’t know, oxybenzone and octinoxate are characterized as “Hazardous to the aquatic environment, long-term hazard » by the United Nations Global Harmonized System (GHS). As they leach off the skin – in the shower or swimming in the ocean – these compounds wash off into various water sources with insidious consequences on aquatic and marine life.

Oxybenzone and octinoxate are ubiquitous environmental contaminants and are found in streams, rivers, and lakes and in marine environments from the Arctic Circle (Barrow, Alaska) to the beaches and coral reefs along the equator [1-7]. They can be found in swimming pools and hot tubs, and even in our drinking water (municipal treated and desalinated sources).
Oxybenzone and octinoxate may also bio-accumulate and be biomagnified in organisms [8, 9]. Biomagnification means they may increase in concentration in the tissues of organisms as it travels up the food chain. A number of aquatic and marine species have been discovered to be contaminated, from carp, catfish, eel, white fish, trout, barb, chub, perch and mussels to coral, mahi-mahi, dolphins, sea turtle eggs, and migratory bird eggs [10, 11]. Finally, additional testings have revealed oxybenzone also acts as an endocrine disruptor on marine invertebrates such as shrimps and bivalves [12]. Other ingredients commonly found in cosmetics – such as butylparaben, octocrylene and a chemical called 4MBC – have proven highly toxic to marine life. You can find the full list at

These compounds eventually disperse in oceanic currents, accumulate in sediments or are absorbed by organisms where they can have devastating effects on invertebrates especially on juvenile development stages [13]. Downs et al. (2015) quantified impacts at the scale of coral fragments and coral polyps, showing death at certain concentrations within the conditions of an experimental tank. Laboratory testing showed that exposure to oxybenzone can inhibit and alter the growth of baby corals, is toxic to seven coral species and is likely to induce coral bleaching in the wild [13]. 

Exposure to oxybenzone or octinoxate causes a healthy coral fragment (left) to bleach within 14 days (right) at concentrations starting from 1 part per billion (octinoxate) and 500 part per trillion (oxybenzone). Source:

Oxybenzone and octinoxate both induce coral bleaching and DNA damage at concentrations starting from one drop worth in an area the size of six and half Olympic swimming pools [13]. That means that in highly touristic areas – particularly in heavily frequented, closed systems such as coves - sunscreen pollution should be addressed as an environmental hazard. Meanwhile, sunscreen manufacturers require “sound scientific evidence proving that, under naturally occurring conditions, sunscreen ingredients are contributing to coral-reef decline”. Scientists have however seen a clear effect on highly frequented – and contaminated - reefs in Maui and claim it is enough evidence to justify a ban [13].
What I think? Considering the critical state of coral reefs worldwide, applying the precautionary principle by promoting chemical-free and other mineral-based sunscreens on highly frequented coral reefs and coastal areas would take some pressure off these fragile ecosystems in decline. Besides, by switching to mineral sunscreens we will also be doing a favor to our skins and personal health. We don’t mention enough the skin and health impacts reported from exposure to these two ingredients in cosmetics. This will change in my next blog ;-)

  • Oxybenzone is used in 70% of cosmetic products as a UV-filter
  • Even a drop of oxybenzone in an ocean area the size of six-and-a-half Olympic swimming pools can damage corals. Researchers found concentrations 12 times that rate in popular waters off Hawaii.
  • Oxybenzone can be detected in urine within 30 minutes of application. If you live in a town near a coral reef and without a sophisticated sewage treatment, flushing the toilet or washing off sunscreen in the shower will impact reefs nearby.
  • Be Sun Smart: wear protective clothing (a long-sleeve shirt, rash guard or wetsuit). Apply lotion to face and ears, neck, feet and back of hands.
  • Let it soak in! Apply sunscreen at least 20 minutes before entering the ocean
  • Make the switch to mineral sunscreens, using zinc oxide or titanium dioxide as UV-filter.
  • Give up skincare that contains Oxybenzone, octinoxate, octocrylene, 4MBC, butylparaben and other nasty chemicals…they are bad for the skin anyways.

1. Tsui, M.M., et al., Seasonal occurrence, removal efficiencies and preliminary risk assessment of multiple classes of organic UV filters in wastewater treatment plants. Water research, 2014. 53: p. 58-67.

2. Tsui, M.M., et al., Occurrence, distribution and ecological risk assessment of multiple classes of UV filters in marine sediments in Hong Kong and Japan. Journal of hazardous materials, 2015. 292: p. 180-187.

3. Balmer, M.E., et al., Occurrence of some organic UV filters in wastewater, in surface waters, and in fish from Swiss lakes. Environmental science & technology, 2005. 39(4): p. 953-962.

4.  Tashiro, Y. and Y. Kameda, Concentration of organic sun-blocking agents in seawater of beaches and coral reefs of Okinawa Island, Japan. Marine pollution bulletin, 2013. 77(1-2): p. 333-340.

5. Sang, Z. and K.S.-Y. Leung, Environmental occurrence and ecological risk assessment of organic UV filters in marine organisms from Hong Kong coastal waters. Science of the Total Environment, 2016. 566: p. 489-498.

6. Bachelot, M., et al., Organic UV filter concentrations in marine mussels from French coastal regions. Science of the Total Environment, 2012. 420: p. 273-279.

7. Rodríguez, A.S., M.R. Sanz, and J.B. Rodríguez, Occurrence of eight UV filters in beaches of Gran Canaria (Canary Islands). An approach to environmental risk assessment. Chemosphere, 2015. 131: p. 85-90.

8. Gago-Ferrero, P., M.S. Díaz-Cruz, and D. Barceló, UV filters bioaccumulation in fish from Iberian river basins. Science of the Total Environment, 2015. 518: p. 518-525.

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