Road traffic is not only choking up the thin layer of atmosphere that has evolved over billions of years to protect life against solar radiation. It’s sending huge amounts of plastic particles on a toxic aerial conveyor belt to climate-shocked areas.
This could speed up warming in sensitive regions, a new study led by the Norwegian Institute for Air Research has found.
Released on Tuesday, 14 July 2020, in the journal Nature Communications, the study warns that traffic arteries are spitting out such a staggering quantity of microplastics that these are being picked up and spread across the globe by atmospheric transport such as wind.
Hitching a ride on atmospheric pathways, thousands upon thousands of tons of tiny plastic particles are disembarking at some of Earth’s most far-flung and pristine corners, such as the Arctic.
Think of these pathways as airborne delivery systems dumping the same amount of plastic into our oceans as polluted rivers across the world.
“In recent years, marine, freshwater and terrestrial pollution with microplastics has been discussed extensively, whereas atmospheric microplastic transport has been largely overlooked,” the authors note.
According to the study, road microplastics arise from brake and tyre wear — more specifically, mechanical abrasion and corrosion.
“Other sources include polymer-modified bitumen, used for road pavements or road-marking paint,” it notes.
Although the health impacts of plastic waste in humans and animals are widely known (asthma, for instance), the study highlights that the “rate of new plastic products continues to increase”. Plainly speaking, this means that “ever greater quantities evade waste collection and recycling”.
Even so, the full ecological and environmental effects of humanity’s love affair with plastic are still “poorly understood” — and these include the routes these materials take to hijack the planet’s life-support systems.
To probe the global movement of road microplastics, the researchers conducted simulations of pathways via the atmosphere.
Using these means, they determined that emissions from road microplastics constitute a significant 30% of total microplastic pollution.
Less surprisingly, the study highlights most heavily urbanised, populated regions such as Asia, Latin America, eastern US, northern Europe and the Middle East as plastic-distribution hotspots.
The biggest particles do not concern this study as much as smaller microplastics, which it defines as units that are no bigger than 2.5 micrometres.
“Larger particles were deposited close to the source of production,” the study adds, while small-size road plastics are more insidious and easily whisked away by atmospheric pathways. “They can remain airborne for long periods.”
According to the study’s estimates, an annual microplastic soup equal to 52,000 tons are pouring into the world’s oceans as a result of this phenomenon; and atmospheric pathways are depositing around 20,000 tons of the stuff, like deadly confetti, on “remote snow- and ice-covered surfaces” such as polar regions and mountain tops.
In areas that are warming faster as a result of their sensitivity to fossil fuels, the concept “surface albedo” is especially important — this is the quantity of sunlight bounced back by the Earth’s surface.
Rather than reflecting sunlight, however, dark microplastics “decrease surface albedo” (thus, collect more heat).
This reverse effect could “hasten melting” in wildernesses such as the Arctic, already teetering on a delicate edge due to global warming.
“In addition,” the study says, “road microplastics may concentrate in Arctic melt pools, with unknown ecological consequences.”
Some recent predictions suggest that the Arctic could be ice-free in as little as 15 years.
None of this is to say that these road microplastics simply enjoy a one-way journey to a single destination and stay there indefinitely. They may be far more well-travelled than that.
“Strong winds may remobilise deposited microplastic particles both from the land and the ocean surface, allowing secondary transport of these particles,” the study warns.
“Another important aspect is the fact that emissions from non-road vehicles (tractors, mining trucks and equipment, construction and forestry machinery, and even military), have not been included in our emission inventories,” the authors say, suggesting that we are a long way from understanding the full consequences of transport-related microplastics.
“While these vehicles are fewer, they work in difficult conditions, are heavier and carry heavy loads leading to enhanced tyre and brake wear.” DM