Microplastics Discovered in Sea Breeze May Explain Where Ocean's Missing Plastic Has Gone

Microplastics have been discovered in sea spray, indicating that large quantities of the tiny particles are potentially being ejected into the atmosphere around the world, researchers have said.

Plastic pollution is ubiquitous in the world's oceans, but scientists have generally assumed that once plastics enter the marine environment it stays there.

However, in a study published in the journal PLOS One, researchers led by Steve Allen and Deonie Allen, from the University of Strathclyde, U.K., suggest some plastic particles could be leaving the sea and entering the atmosphere.

There are two main sources of microplastics—generally defined as tiny pieces of plastic measuring less than 0.2 inches across. The first is the fragmentation of larger pieces of plastic in the ocean that break down into smaller pieces over time. The second is microplastics that are already this small when they are manufactured, such as microbeads, directly entering the oceans.

Microplastics have been documented everywhere from the seafloor to the surface waters of the remote Arctic. Recently, researchers even discovered microplastics in the body of a new species that lives in Earth's deepest ocean trench.

In 2018, around 359 million tons of plastic were produced globally. One study from 2015 estimated that roughly 10 percent of the plastic produced every year eventually makes its way into the sea. Meanwhile, another estimate suggested that in 2010, between 4.8–12.7 million tons of plastic entered the oceans from coastal and terrestrial areas.

"That this figure is now 10 years old and as around half of all plastics produced has been in the last 15 years, it is likely that figure would significantly underestimate current levels," the authors wrote in the study.

However, despite efforts to model the movement of plastic in the oceans, researchers say there is still a significant quantity of "missing plastic" that is unaccounted for.

"We have an estimated 12 million tonnes entering the sea every year but scientists have not managed to find where most of it goes—except in whales and other sea creatures— so we looked to see if some could be coming back out," Steve and Deonie Allen told Newsweek.

In the latest study, researchers analyzed water droplets from sea spray at Mimizan beach on the south-west Atlantic coast of France, detecting microplastics measuring between five and 140 micrometers across.

"Microplastic is coming back out of the sea in high numbers. We expected that it was likely happening, but 19 particles per cubic meter of air was surprisingly high considering we tested a low-pollution body of water," the authors told Newsweek.

To detect the microplastics in the sea spray, the researchers used two types of sampler: "One was a simple vacuum pump and filter. The other is a 'cloud catcher' designed to sample water droplets in clouds on mountain tops. It uses tiny filaments of Teflon to capture the drops, which then run into our sample bottle. It turns out they do different jobs and gave us interesting comparisons," they said.

They estimate that up to 136,000 tons of microplastics could be expelled from the sea every year around the world. The microplastics may be ejected into the atmosphere when breaking waves cause bubbles of trapped air to rise to the surface and burst, according to the researchers.

"Once 10 meters above surface level the plastics can be transported like any other airborne particle," the authors told Newsweek. "Our understanding is that it can pretty much go anywhere and everywhere. This study shows that it is likely you are breathing in microplastic if you have an onshore wind. We are still researching to see if it is a higher exposure than, say, being in the city or wearing plastic clothing."

This so-called "bubble burst ejection" phenomenon is already known to eject tiny salt particles in the air, which are then transported by the wind. But this the first time that microplastics have been shown to be released by the same process.

"Sea breeze has traditionally been considered 'clean air' but this study shows surprising amounts of microplastic particles being carried by it." Steve Allen told The Guardian. "It appears that some plastic particles could be leaving the sea and entering the atmosphere. 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. The ocean is giving it back to us."

Allen said the way plastic is transported around marine environments is "complicated."

"We know plastic comes out of rivers into the sea," he told The Guardian. "Some goes into gyres, some sinks and goes into the sediment, but the quantity on the seafloor doesn't match the amount of plastic that would make up this equation. There's a quantity of missing plastic."

The team say that the latest results could shed light on where some of this missing plastic ends up. Previous research has shown that tiny microplastics can be transported in the atmosphere by the wind over large distances.

"We know plastic moves in the atmosphere, we know it moves in water. Now we know it can come back. It is the first opening line of a new discussion," Allen said.

"The ocean is not a dumping ground. It is throwing our rubbish back at us and this is telling us we need to change our relationship with plastic and our planet," the authors told Newsweek. "Recycling is not going to stop this problem. Reduction and refusal to accept unnecessary plastic are the best way forward."

This article was updated to include additional comments from Steve Allen and Deonie Allen.