Taking an ocean dip after slathering on sunblock could damage the undersea ecosystem.
That's the conclusion of a recently published study in the Journal of Environmental Science and Technology that shows how chemicals in sunscreen have the potential to wreak havoc on marine life.
The problem? Certain kinds of sunblock react with the sun's rays when they hit the water to create hydrogen peroxide, a compound found in bleach and household cleaning products. Unfortunately for the aquatic environment, the substance used to keep kitchen counters sparkling clean can also prove toxic to plants that are essential to the underwater food chain.
The study's authors—Spanish researchers working on the Mediterranean island of Majorca—analyzed sea water samples to support that point. They found that tiny particles of zinc oxide and titanium dioxide, commonly used sunscreen ingredients, can undergo a chemical reaction after coming into contact with ultraviolet rays.
That, in turn, can damage phytoplankton, a microscopic form of algae that makes its home everywhere from coral reefs to tidal pools. The sunlight-loving plant serves as a vital source of nutrition for small fish and marine animals as massive as dolphins and whales.
Researchers discovered high concentrations of hydrogen peroxide in coastal waters after sunscreen-laden swimmers descended upon the beaches at the height of tourist season.
"Here in Majorca we have a lot of tourists, and the chemicals in the sunscreen wash off when people go into the water. That is really problematic," said David Sánchez Quiles, one of the lead authors of the report.
When it comes to environmental impacts associated with sunblock, not all are created equal. The study indicated that the sunscreens that morphed into hydrogen peroxide were ones made using nanotechnology, a process that involves breaking down and manipulating particles at the molecular and atomic scale.
Sunscreen with nanoparticles have become popular thanks to public demand for creams and sprays that absorb into the skin without leaving a white residue behind. But research suggests that the chemical compounds may be more unstable than traditional sunblock, a feature of the technology that could pose problems for humans and the environment.
An earlier study, published in April, found that nanoparticles from sunscreen sometimes accumulate in coral-reef ecosystems. The research concluded that the buildup of chemicals could endanger the coral.
"Sure, nobody wants to look like a snowman when you go to the beach, but there are some serious health and environmental concerns that come along with these products and right now consumers aren't all that aware of the potential risks," warned Ian Illuminato, a health and environmental campaigner with Friends of the Earth.
In Europe, sunscreen manufacturers must label products made with nanoparticles. But the United States has no such requirement. The Food and Drug Administration does not compel companies to alert consumers to the presence of the microscopic ingredients in sunblock.
That, environmentalists and researchers say, is a major problem. "This is something that you use in your daily life and it's important for these products to be labeled properly so that people know what they're buying and understand what the impacts are," Sánchez Quiles said.