Those microscopic plastic particles emitted by car tyres and brakes can't possibly be harmful, right? They're so small and almost imperceptible, but they're deadly. Did you know that road microplastics produce over 200,000 tonnes of microscopic plastic particles each year, which end up in the oceans?
The study, titled "Atmospheric Transport is a Major Pathway of Microplastics to Remote Regions," was published in Nature Communications in July 2020. The study used two methods to estimate the amounts of fine particles emitted by tyres & brakes, as well as well-established atmospheric circulation models to assess how the particles are blown around the world.
Findings of Study:
Tire wear particles (TWPs) and brake wear particles (BWPs) were the focus of the research team's global simulations of microplastic particle transport in the atmosphere. TWPs and BWPs are produced by mechanical abrasion and corrosion, respectively, and both are reasonably quantifiable. Microplastic particles with mean sizes ranging from 0.5 to 9.5 m can linger in the atmosphere for extended periods of time.
"Roads are a very significant source of microplastics to remote areas, including the oceans," said Andreas Stohl, lead researcher at the Norwegian Institute for Air Research. According to him, the average tyre loses 4 kg over its lifetime. "It's such a huge amount of plastic compared to, say, clothes," Stohl said, whose fibres are commonly found in rivers. "Unlike vehicle tyres and brakes, you will not lose kilogrammes of plastic from your clothing."
Why are Tyres & Brakes such major sources of microplastics?
Road traffic emissions are a significant source of plastics. Motorcycles, cars, light-duty vehicles, buses, and heavy-duty vehicles are examples of notable road transport vehicle types. The estimates of distance driven for this study were derived using data on road transport fuel use, which was supported by national data on vehicle numbers and per-vehicle mileage travelled assumptions.
Tyres are made up of a variety of elastomers, including natural and synthetic rubber, carbon black, steel cord, fibres, and other organic and inorganic components that improve their stability. The majority of car braking systems are made up of a disc or drum with a pair of shoes or pads mounted in callipers. Binders, fibres, fillers, frictional additives or lubricants, and abrasives make up brake linings.
In the study, two different approaches were used to calculate the global emissions of road microplastics. The researchers used CO2 emissions from the Coupled Model Intercomparison Project inventory to assume a constant ratio of TWP emissions to CO2 emissions from the road transport sector. Northern Europe provided detailed information on TWP emissions.
They also used the GAINS (Greenhouse gas–Air pollution Interactions and Synergies) model, which is an integrated assessment model that estimates emissions of air pollutants and Kyoto gases in nearly 200 regions around the world.
The model takes into account key economic activities, environmental regulation policies, and emission factors that vary by region. Non-exhaust PM emissions in GAINS include TWPs, BWPs, and road abrasion, and the calculation is based on region-specific data and distance-driven estimates.
According to the study's cumulative data, emissions of road microplastics are concentrated in the eastern United States, northern Europe, and large urbanized areas of eastern China, the Middle East, and Latin America. This makes sense because these are the areas with the highest vehicle densities.
The transport efficiency was defined by the researchers as the ratio of the mass of microplastics deposited in a remote area to the total mass of microplastics emitted globally. Coarse particles were more efficiently deposited than fine particles in areas surrounded by road microplastic emissions sources.
Reducing microplastic pollution in society as a whole is a huge challenge, as is the more specific goal of eliminating road microplastic pollution from vehicles. "The manufacturers will have to respond in some way if this truly becomes a matter of concern," said Stohl, the lead researcher. Until more communities are concerned about microplastic pollution, Stohl recommends that people reduce their use of plastics they can do without and recycle the rest.
(Source: Clean Technica)
