Nevertheless, vehicles  generate not only gas emissions but also non-exhaust emissions (NEE). NEE are particles released into the air from brake wear, tyre wear, road surface wear and resuspension of road dust during  vehicle movement.  The UK Government’s Air Quality Expert Group (2019) reported that PM 2.5 is composed of those particles 60% (by mass) as well as 73% by mass in PM 10. So, NEE are a part of the ongoing air pollution problem  in UK cities which is related to respiratory illnesses. [2] Corresponding with recently study from Emissions Analytics, air pollution from tyre wear particles can be 1,000 times worse than car’s exhaust. [3]

Some people might think car tyres are made from 100 % natural rubber.  Actually they are not... Technically, tyres are composed of natural rubber only 19 % and the rest are  synthetic rubber 24%, fabric, wire, along with carbon black and other chemical compounds.[4]  During we are driving, tyres interact with road surface and finally throw off tiny synthetic rubbers (plastic polymers) which their size are classified as Microplatic  and finally  end up in rivers or  oceans. [Figure 1 ]

Figure 1 : Tyre Wear Particles [5]

Tyre wear considers to be one of a “Top 10” list of plastic pollution sources that the public should be aware of in their daily lives and request a priority from the UK government to take action. [Figure 2] and also be a major microplastic pollutant with the amount  more than 19,000 tonnes could be entering UK waterways every year. [Figure 3]

Figure 3 : Estimates for Key Sources of Plastic Pollution to  Surface Waters from 

                   the UK from land-based sources.[6]

References :

[1] AZoCleantech (2008, Jan 29).What are Vehicle Exhaust Emissions?

https://www.azocleantech.com/article.aspx?ArticleID=39