Waves on the ocean throw back environmental toxins

16 December, 2021

Environmental toxins collected in the sea return to land when waves break on the sea surface, a Swedish study shows.

The conclusion means that the poisons are more difficult to get rid of than previously known.

Highly fluorinated PFAS substances, i.e. chemicals produced to, for example, repel grease and water, accumulate in watercourses and eventually flow into the sea. The researchers have previously assumed that the toxic substances are gradually diluted and end up in the deep ocean, but a study from Stockholm University overturns the previous theory by showing that waves on the sea surface throw the substances back to land.

– We have discovered that they can be moved from the ocean to the atmosphere with the help of seawater particles. In this way, they can circulate between sea and air, travel hundreds of kilometers and be in the atmosphere for several weeks, says Jana Johansson, co-author of the study and researcher at the Department of Environmental Science at Stockholm University.

Bursting bubbles

PFAS substances settle as a concentrated film on the sea surface and rise into the atmosphere with the help of so-called sea spray, which is created by bursting air bubbles when the waves break.

The discovery means that PFAS substances can pose a bigger environmental problem than was previously known. It is still unclear whether PFAS substances returning from the sea end up in food on land.

Keeps spinning around

– For us who live on land, the consequences are that this is an environmental problem that we will have to live with for a very long time. Even if we implement measures to reduce emissions, it will continue to spin around and end up in our ecosystems, says Johansson and continues.

– It is difficult to do anything about emissions that occurred 50 years ago, but we can learn from it and not release substances that are difficult to break down in nature, water-soluble and surface-active.

The study has been published in the scientific journal Environmental Science & Technology.

PFAS (poly- and perfluorinated alkyl substances) do not occur naturally, but began to be produced on a larger scale in the 1950s.

PFAS is a collective name for approximately 4,700 different industrially produced substances with a similar structure and partially shared properties.

PFAS contain fluorine atoms in special places and the molecules are characterized by having a water-soluble and a fat-soluble side. This gives them special surface properties, which are used, for example, to make durable bubbles in fire foam, good sliding in ski wax and water-repellent impregnation for textiles and floors.

Other areas of use are coating in frying pans and in certain types of food packaging, for example for hamburgers, popcorn and on sandwich paper.

PFAS are very long-lived compounds, which break down extremely slowly. Once they end up in the wild, they stay. Therefore, they are a difficult problem in, for example, water sources.

Within the EU, it has been banned since 2008 to use PFOS and since 2020 it has been banned to use PFOA (PFOS and PFOA are “long-chain” forms of PFAS that are considered more problematic).

In September of last year, the European Food Safety Authority (EFSA) developed new health-based limit values ​​for the PFAS family, and they are to be implemented in Sweden within two years.

Sources: The National Encyclopedia and the Swedish Food Agency

Text: Erik Paulsson Rönnbäck/TT
Photo: Adam Ihse/TT

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