Fish don't need sunscreen, scientists say

A beach in Majorca, Spain. Colourful towels line the beach and children play in the sand. The smell of salt and sunscreen fill the air.

These are a small fraction of the tourists who flock to the Mediterranean every year – the world’s most popular tourist destination, according to the United Nations World Tourism Organisation. In 2013, more than 202 million tourists arrived in the region, many heading to the beaches. That number is expected to grow by another 3 million per year by 2030.

With so much naked skin sticking out and the sun glaring down, tourists slather the sunscreen on. But a new study has found that many of these sunscreens form hydrogen peroxide in the ocean when they soak up UV rays. Hydrogen peroxide can kill or damage phytoplankton, and if phytoplankton is in trouble, this could have reverberations up the marine food chain – especially since so many animals (from whales to shrimp) rely on phytoplankton as a food source.

“Use of sunscreens has proven the most effective method to prevent a great number of skin diseases,” David Sánchez Quiles, one of the lead authors of the study told us. “However, due to its chemical composition it is far from being environmental-friendly. In fact, previous studies have suggested that it should be labelled as an environmental hazard substance.”

Though we may not realise it, when masses of people go for a dip, an estimated 4,000 to 6,000 metric tons of sunscreen are released into the ocean yearly. The ocean is huge, but 4 to 6,000 metric tons is still significant. It doesn't help that the market for sun care products has grown by about 7 percent yearly over the last 5 years.

“The production and use of sunscreen products are increasingly and exclusively concentrated in coastal environments,” Dr. Cinzia Corinaldesi, professor of ecology at Polytechnic University of Marche in Italy, told us. “Sunscreen products are largely used by tourists, and mostly released during their baths, and coastal waters are among the most biologically productive and rich in biodiversity of the world,”

Phytoplankton Bloom, Bay of Biscay. Image: NASA Goddard Space Flight Center/CC BY 2.0

In lab tests, Sánchez Quiles and his colleague Antonio Tovar-Sanchez found that after 22 hours, one gram of sunscreen in one litre of sea water produced about 46 times more hydrogen peroxide than seawater without sunscreen.

They also found another worrying issue: titanium dioxide nanoparticles (found in many sunscreens) are not water soluble and could accumulate in the ocean, where they would continuously form hydrogen peroxide. Because nanoparticles are so small (as their name suggests), they could also be ingested by worms and starfish living on the ocean floor.

Sánchez Quiles told us more studies will be needed to understand just how big of a problem this could be.

This is not the first study to raise concerns about the effect sunscreen has on the ocean. In 2008, Corinaldesi was part of a team that found that sunscreen may be contributing to coral bleaching. But she reassured us that there are environmentally friendly options out there. “Soveè (by Aethic) and the MarineCare (by Ecoreach) are produced from an international patent developed after the discoveries made by the researchers of Polytechnic University of Marche,” she said.

She also added that some forms of titanium dioxide particles were not as reactive to UV rays and were considered eco-compatible. “There is a need to deepen our knowledge about the impact on marine life and to explain how important it is to use new eco-compatible products instead of the classical sunscreens, in order to promote the use of non-dangerous personal care products for marine life and at the same time safe for humans.”

Tags: Conservation | Oceans

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