Tires and Microplastics
Tire wear is one of the primary sources of microplastic pollution in the atmosphere, soil, and water bodies. Mechanical friction between the tires and the road surface allows small particles from the tires to detach and enter the environment. These particles are sources of microplastics (MPs) less than 5 mm in size and are partly referred to as particulate matter (PM). In two European countries, tires are reported to be responsible for 30-50% of total microplastic emissions [1]. According to IUCN, tire wear and tear contribute to 23-28% of water pollution, 3-7% of atmospheric fine particulate matter (PM2.5) [2], and 70% of the remaining contributed to soil pollution [3].
Tire formula contains a wide range of materials such as natural rubber, synthetic polymers (butadiene rubber, styrene-butadiene rubber, and halogenated polyisobutylene rubber), fillers (carbon black and amorphous silica), metal, textile (polyester, nylon, rayon, and aramid), curing materials (zinc oxide and sulfur), and other additives. New tires have lower MPs exposures. However, the older they get, the more easily mechanical friction with the road can detach the damaged parts. Therefore, toxicity levels should also follow the latter discipline: the older the tire, the higher the exposure and the greater the leaching of chemicals.
Every year, more than 1.6 billion new tires are produced and one billion discarded while recycling accounts for only about 100 million tires [4]. Discarded tires must be store in open storage sites for recycling for an unknown period or sent directly to landfills, dumping sites, or even incinerators. That means tires continue to pollute soil, air, and water even after they are no longer on the road. It takes about 100 years for a discarded tire to decompose, posing a major problem for the environment.
So far, the best way to reduce the negative impacts of tires is recycling, assuming the products are of good quality and meet health standards. For tire landfills, a leachate collection system is required for further treatment and subsequent separation of the microplastic.
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References
1-Baensch-Baltruschat, Beate, Birgit Kocher, Friederike Stock, and Georg Reifferscheid. "Tyre and road wear particles (TRWP)-A review of generation, properties, emissions, human health risk, ecotoxicity, and fate in the environment." Science of the total Environment 733 (2020).
2-Kole, P.J., Löhr, A.J., Van Belleghem, F.G. and Ragas, A.M., 2017. Wear and tear of tyres: a stealthy source of microplastics in the environment. International journal of environmental research and public health, 14(10).
3-Baensch-Baltruschat, B., Kocher, B., Kochleus, C., Stock, F. and Reifferscheid, G., 2021. Tyre and road wear particles-a calculation of generation, transport and release to water and soil with special regard to German roads. Science of the Total Environment, 752.
I had an interesting conversation on this with a researcher recently, and I asked her about the impact of electric cars and tyres because I'd read that electric cars being heavier due to the battery weight, it increases the particulates from tyres. This seems to be the case, have you seen any research on this Mitra Nikpay
Great article! Keep up the good work.