Bather-borne chemicals cause coral bleaching and wider damage to marine ecosystems and coastal communities
by Craig Weatherby
Excessive sun avoidance and sunscreen use may contribute to the current epidemic of vitamin D deficiency.
But the beach is one place where light-skinned people really need the UV-blocking chemical creams, or suffer painful sunburns that can promote cancer.
Unfortunately, it now appears like the sunscreen residues that wash off ocean bathers represent a major cause of coral bleaching.
Coral reefs are prolifically productive ecosystems that sustain fish populations—and the estimated one-half billion people who depend on reef-related fisheries.
Sadly, more than half of these critical reef ecosystems are threatened by climate change (i.e., warming waters), industrial pollution, and increasing UV radiation (via loss of atmospheric ozone).
An estimated 78 million tourists visit coral reefs annually, and the implications of this huge number are alarming, in light of new findings about sunscreens' killer impact on coral.
Sunscreen chemicals kill coral very quickly
Researchers have detected chemical ingredients from sunscreens and other body lotions near both sea and freshwater tourist areas.
These chemicals can accumulate in aquatic animals, and break down into toxic byproducts.
The new findings flow from a study ordered by the European Commission, which was conducted by Italian researchers from the University of Pisa (Danovaro R et al. 2008).
The Italian team added measured amounts of three brands of sunscreen to the waters near coral reefs off the coasts of Mexico, Indonesia, Thailand, and Egypt.
Sadly, even trace levels of the chemicals caused coral to discharge large amounts of mucous within two days, while complete bleaching of coral occurred within four days (Mucous release is a known sign of severe coral stress).
In addition, levels of viruses in the water surrounding coral branches increased 15-fold: a finding that comports with the effects of other synthetic pollutants and indicates that chemicals in sunscreen promote latent viral infections in the tiny animals that create coral reefs.
The Italians found that four common sunscreen ingredients “awaken” dormant viruses in the symbiotic algae (zooxanthellae) that live inside tiny reef-building coral animals. The ingredients in question are paraben (a B-vitamin complex chemical), cinnamate, benzophenone, and a camphor derivative.
As they wrote, “We conclude that sunscreens, by promoting viral infection, potentially play an important role in coral bleaching in areas prone to high levels of recreational use by humans” (Danovaro R et al. 2008).
These algae sustain coral with energy provided through photosynthesis, and also contribute to the vibrant color that characterizes coral reefs. Without these algae, the coral turns white and dies.
The implications of these findings are alarming, given the following facts:
- Bathers release about 5,000 tons of sunscreen in reef areas every year.
- Fully one-fourth of the sunscreen ingredients applied to skin wash off after only 20 minutes of submersion in ocean water.
The lesson seems to be that we should not wear sunscreen anywhere near coral reefs, and instead wear sun-blocking garments into the water.
Sadly, sunscreen avoidance seems an unlikely outcome of the new findings, given that swimming and snorkeling in sunny waters—sans shirt and pants—is a primary purpose of most people's tropical trips.
The only solution might be development—and successful marketing—of new, form-fitting, sun-blocking, “coral-saving” garments designed for swimming in warm waters.
- Danovaro R, Bongiorni L, Corinaldesi C, Giovannelli D, Damiani E, Astolfi P, Greci L, Pusceddu A. Sunscreens cause coral bleaching by promoting viral infections. Environ Health Perspect. 2008 Apr;116(4):441-7.
- Than K. Swimmers' Sunscreen Killing Off Coral. January 29, 2008. National Geographic News. Accessed online May 30, 2008 at http://news.nationalgeographic.com/news/2008/01/080129-sunscreen-coral.html