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Study shows the sea breeze is bringing ocean plastic pollution back onto land

Waves approaching the shoreline. Credit: Mario Guti

A study has found that hundreds of thousands of tonnes of microplastics could be blowing ashore on the sea breeze every year.

While awareness of plastic pollution in the oceans has been growing in recent years it has been assumed until now that plastic which ends up in the sea stays there.

Now a new study by the University of Strathclyde and Observatoire Midi-Pyrénées (CNRS-University of Toulouse), has found evidence that microplastics could be ejected by sea spray, released into the atmosphere and transported back onto land.

The researchers reviewed evidence from existing literature relevant to this theory and followed up with a pilot study which analysed microplastics in sea spray at Mimizan beach in Aquitaine on the south-west Atlantic coast of France.

Bubble burst

Over the course of a week the team used a ‘cloud catcher’ machine and pumped filters to capture water droplets and analysed them for microplastics, sampling various wind directions and speeds including a storm and sea fog event.

They found plastic fragments as small as five micrometres and up to 140 micrometres-long fibres in the air suggesting that it is being ejected by the sea in bubbles. The sea fog generated by the surf produced the highest counts of 19 plastic particles per cubic meter of air.

The results, published in the journal PLoS One, show that microplastics in the ocean could be transferred to the air by the process of ‘bubble burst ejection’ and ‘wave action’, for example from strong wind or turbulent seas.

Previous studies have already shown that microplastics can be transported long distances in the atmosphere by wind, including work by the same researchers which found microplastic pollution in a remote region of the Pyrenees mountains.

According to the plastic industries' figures, around 359 million tons of plastic was manufactured globally in 2018 with some estimates suggesting that around 10% of all plastic produced is lost to the sea each year.

Surprising amounts

Steve Allen, a Strathclyde PhD candidate who co-led the study, said: “Sea breeze has traditionally been considered ‘clean air’ but this study shows surprising amounts of microplastic particles being carried by it.

“It appears that some plastic particles could be leaving the sea and entering the atmosphere along with sea salt, bacteria, viruses and algae.

“Bubble ejection of particles is a well-known phenomenon but we have now shown that microplastic is also being ejected from the sea. To date, there has been no consideration of the oceans as an atmospheric microplastic source.

We keep putting millions of tonnes of plastic into the ocean every year, this research shows that it is not going to stay there forever.”

Co-research lead Dr Deonie Allen of Strathclyde added: “Where the oceanic plastics being ‘lost’ is relatively unknown and this research adds a small but important piece to the puzzle.

“We don’t know a lot about the effect on humans but a growing number of studies are showing there is a potential danger from inhalation of microplastic particles”.

The data has been funded by GET and WESP (University of Strathclyde) research department support.

The research leading to these results has also received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement number PCOFUND-GA-2013-609102, through the PRESTIGE programme coordinated by Campus France.