Most of our plastic waste is buried in landfills, incinerated or recycled, but up to 18% ends up in the environment. Since plastic is not easily degradable, it fragments into smaller and smaller pieces until the microplastics are small enough to be swept into the air.
This means that much of the plastic that is dumped in the sea and on land is broken down and spit out again, posing potential risks to our ecosystems. And while some progress has been made in making biodegradable polymers, the researchers warned that microplastics “will continue to circulate through Earth’s systems.”
The research team collected atmospheric microplastic data from the western United States from 2017 to 2019 and found that an estimated 22,000 tons of microplastics are deposited in the US every year.
In the US, plastic is thrown into the air via road traffic. Car tires, brakes and even road surfaces contain plastic, which can be worn down into microplastics that are released into the atmosphere. The turbulence of cars on the road – the movement of tires, the braking process, the exhaust gases they emit – all help churn plastic on the ground and send it to the sky, the study said.
This also happens in the ocean, where large clusters of waste form entire plastic islands. They break down into plastic particles that sit on the top layer of the water, where they are flung into the air by waves and wind.
There are several other ways that microplastics end up in the atmosphere, in large cities by the wind and on farms via soil dust during agricultural processes.
Once in the atmosphere, plastics can remain in the air for up to six and a half days, according to the study. Within this time, “under the right conditions, plastic can be transported across the great oceans and between continents, either in one trip or by resuspension across the oceans,” the study said.
The US, Europe, the Middle East, India and East Asia are hot spots for land-based plastic deposition, the study said. Meanwhile, oceanic sources of airborne plastic are more prominent along the coasts, including the west coast of the US, the Mediterranean and southern Australia. Dust and agricultural sources of microplastics are more common in North Africa and Eurasia, while microplastics from road traffic make an important contribution in “densely populated regions” worldwide.
“Inhaling particles can irritate lung tissue and lead to serious illness, but whether plastics are more or less toxic than other aerosols is not yet well understood,” the study said. It added that further research is also needed to understand the impact of several factors, including population density and ocean circulation.
The researchers also called for better management of plastic waste.
“Our relative ignorance of the consequences, despite the rapidly increasing plastic concentrations in our environment, highlights the importance of improving the management of plastic waste or, indeed, capturing plastic from the ocean and removing it from the system,” said the study.