Here's how your sunscreen pollutes beaches, harms aquatic life

Applying sunscreen on your body may be good for your skin, but not so much for the fish, a new study has revealed.

Scientists have found that sunscreen from the body of bathers releases significant quantities of polluting titanium dioxide (TiO2) into the sea, which has the potential to harm marine life.

TiO2 is one of the main ingredients of sunscreen and acts as a protective agent against harmful UV rays. Most major regulatory bodies consider it safe for human use at the concentrations used in sunscreens, however, concentrated TiO2 or long-term exposure could be toxic to a variety of fish and other aquatic organisms.

In many sunscreens, TiO2 is present as tiny nanoparticles, which are coated with protective chemicals. Because the particle size is so small, nano-titanium dioxide does not reflect visible light but does absorb UV light, enabling a transparent barrier that protects the skin from the sun's harmful rays.

The researchers have found that in water, the nanoparticles tend to lose their protective coating under the influence of UV light or seawater composition, which exposes the more toxic TiO2 to the aquatic environment.

They measured TiO2 concentrations in 3 beaches near Marseille in France, and surveyed bathers about how much sunscreen they used. The team found daily concentrations of 15 to 45 µg/L of TiO2, which corresponds to several kgs of nanoparticles per summer season at each beach.

The study found that with one small beach, which saw a foot fall of around 3000 people daily, the researchers calculated that around 68kg of cream could be deposited per day or 2.2 tons over the height of summer. Lead Researcher, Dr. Jerome Labille said, "If we consider reasonably that half of the creams used contain 5% of titanium dioxide, this gives 1.7 kg of titanium dioxide released per day. That comes to around 54kg in the two months of high summer, which is a significant amount."

The sea is more or less continually in motion, so some of the titanium dioxide pollutants will be dispersed. Nevertheless, we anticipate an accumulation of the chemical in the seashore littoral, which could affect the aquatic life there. In recreation areas with stagnant water, such as in lakes or seawater swimming pools, there will be no such dispersion and the accumulation would be expected to be even more pronounced.

"It is extremely important that sunbathers continue to use sunscreen for skin protection, the titanium dioxide pollution needs to be dealt with by the manufacturers and possibly legislation, and we've had good feedback from the manufacturers we are working with," said Labille.

The researchers are currently working on developing sunscreens which are "safe by design" in which the release and toxicity of nanoparticles will be minimized.

The findings were discussed in the Goldschmidt 2018 meeting.