Is Your Sunscreen Harming Dolphins and Whales?

Researchers find that two common sunscreen ingredients are toxic to tiny animals that are a food source for marine mammals.

(Photo: David Gray/Reuters)

Aug 21, 2014· 1 MIN READ
Kristine Wong is a regular contributor to TakePart and a multimedia journalist who reports on energy, the environment, sustainable business, and food.

Many of us wear sunscreen to protect our skin. But when that sunscreen washes off in the ocean, it can harm marine life.

A new study shows that two common ingredients in sunscreen—microscopic particles of titanium dioxide and zinc oxide—can combine with ultraviolet sunlight to cause toxic effects in phytoplankton, a food source for small fish, shrimp, and whales.

Given the growth of coastal tourism and the sun care–product market, it’s a timely and important issue, according to David Sánchez-Quiles, a researcher at the University of the Balearic Islands in Spain and coauthor of the study.

“Coastal tourism is, in many countries, among the fastest-growing areas of contemporary tourism,” he said in an email. “And the global market of sun care products has increased an average of seven percent per year over the last five years.”

Here’s what happens: When sunscreen slides off swimmers’ skin into the sea, the tiny particles—also known as nanoparticles—of titanium dioxide and zinc oxide react with ultraviolet light to create hydrogen peroxide. When hydrogen peroxide accumulates at higher levels, it puts a damper on phytoplankton growth. Because larger marine animals feed on the microscopic algae, it could also affect their available food supply.

Hydrogen peroxide is also produced from titanium dioxide nanoparticles that accumulate in beach sediments, said Sánchez-Quiles.

The researchers collected coastal seawater samples from the Mediterranean Sea off Palmira Beach, a popular swimming area on Spain’s Majorca Island. They first measured the levels of UV sunlight and hydrogen peroxide. Then they tested the effect of three sunscreens on phytoplankton by immersing the products in seawater samples exposed to UV sunlight.

Sunscreens with nanoparticles of titanium dioxide and zinc oxide generate more hydrogen peroxide than sunscreens without them, according to Sánchez-Quiles. The major contribution comes from titanium dioxide, he added.

So what can concerned swimmers and surfers do? The bad news is that most sunscreens contain these nanoparticles, despite “non-nano” labels on some products, according to the Environmental Working Group, a nonprofit research organization.

But you can reduce their impact by using cream-based sunscreens instead of spray versions, because the spray products are more water-soluble, Sánchez-Quiles said.

“Environmental scientists and cosmetics companies must work together to compromise between human and environmental health,” he said. “More ecotoxicological analysis, as well as better labeling of sunscreens, can also help to address the issue.”