Last Updated on May 14, 2024 by Ecologica Life
When we talk about vehicle emissions, we tend to think of the exhaust pipe. But think again.
Today’s internal combustion engines have become so advanced that the levels of pollutants they emit are becoming incredibly low – so low, in fact, that they’re often difficult to measure. While these vehicles still emit significant amounts of carbon dioxide, a contributor to in climate change, these emissions don’t directly affect urban air quality.
It can be argued that the largest source of pollutant emissions from new vehicles now comes from non-exhaust sources like brake and tyre wear. This article focuses on tyre wear, which is becoming a major environmental concern.
Table of Contents
Sources of Non-Exhaust Emissions
As consumers opt for bigger, heavier vehicles, tyre wear increases, which in turn releases more microplastics into the environment.
Research shows that these tiny particles don’t just stay on the roads. They enter our air and even our oceans, contributing to microplastic pollution. This type of pollution is unregulated.
What Are Microplastics? Should You Be Worried?
In a 2019 report, the UK government’s Air Quality Expert Group (AQEG) sounded a wake-up call about an overlooked source of pollution – non-exhaust emissions (NEEs) from vehicles.1 The report highlights the urgent need to recognise these emissions as a significant contributor to air pollution, even from vehicles that boast zero exhaust emissions.
Non-exhaust emissions include physical road wear particles from several sources: the physical wearing down of roads by vehicles, the stirring up of particles already on the road, and the wearing down of brakes and tyres. Greater adoption of regenerative braking means that brake wear emissions can be reduced.
However, due to the high weight and poor aerodynamics of sport utility vehicles (SUVs) and the high weight and torque drive characteristics of battery electric vehicles (BEVs), tyre emissions are expected to increase.
This highlights the complex trade-offs in our journey towards cleaner transport and underlines the need for regulations that address all sources of vehicle pollution.
Tyres Now 2000 Times Worse Than Exhausts
Recent tests have shown that modern car tyres can emit almost 2000 times more particulate pollution than their exhaust.
Tyre particles pollute air, water and soil and contain a wide range of toxic organic compounds. Some of these are known carcinogens.
Air pollution is responsible for millions of premature deaths every year. Regulations have ensured that new cars in developed countries have much lower particle emissions. New cars in Europe are generally well below the legal limit. While this should be seen as a triumph for car manufacturers and regulators, it is important that all types of emissions are considered, especially before we go labelling some cars as “zero emission” cars.
Emissions Analytics, a leading independent emissions testing company, found that in the UK and US, 300,000 tonnes of tyre rubber are released into the environment each year from cars and vans alone.
Currently, there are no specific regulations on tyre wear and little regulation on the chemicals they contain. Emissions Analytics has identified the chemicals in 250 different types of tyres, most of which are made from synthetic rubber – a product derived from crude oil. Of the hundreds of chemicals identified, many are carcinogenic.
Impact on Human Health and the Environment
Recent research has increasingly shown that tyre wear is not only a significant air pollutant but also a major contributor to microplastic pollution in the environment. These tiny particles from tyres can affect both terrestrial and aquatic ecosystems.
Impact on Marine Life
Tyre debris is washed off roads into streams, rivers, and eventually oceans. This adds microplastics to the marine environment. These microplastics have been shown to affect a wide range of aquatic organisms, including aquatic mammals.
In particular, a specific chemical commonly used in tyre manufacturing, 6PPD quinone, has been directly linked to significant mortality rates in salmon populations in the United States.2 This chemical, which is designed to extend the life of tyres by preventing degradation due to ozone exposure, is toxic to aquatic life.
We should be careful about the chemicals that we choose in manufacturing because of unintended ecological effects.
Human Health Risks
The impact of tyre pollution on human health is also significant. As tyres degrade, they release fine particles that contribute to particulate matter (PM) pollution in the air.
These particles, particularly those smaller than 10 microns (PM10) and even more so those smaller than 2.5 microns (PM2.5), can penetrate deep into the lungs and even enter the bloodstream.
There is also growing concern about the potential for these particles to carry toxic chemicals into the body. This could have additional toxicological effects.
Solutions
Research
Given the magnitude and potential severity of these impacts, there is an urgent need for more research into the environmental and health effects of tyre debris.
In addition, researchers could investigate strategies to manage and reduce tyre pollution. These could include improvements in tyre composition to reduce hazardous emissions and improvements in road design.
Tyre Regulations
This is not a lost cause. Not all tyres on the road are so polluting. The wear rate of different tyre brands varies considerably. The toxic chemical content of different tyre brands varies even more. This means that low-cost changes can be made to reduce the environmental impact of the worst tyres.
Nick Molden, from Emissions Analytics, had this to say about the subject:
You could do a lot by eliminating the most toxic tyres. It’s not about stopping people driving or having to invent completely new tyres. If you could eliminate the worst half, and maybe bring them in line with the best in class, you can make a massive difference. But at the moment, there’s no regulatory tool, there’s no surveillance.
Nick Molden, Emissions Analytics
What About Electric Cars?
The increasing weight of cars has sparked debate, particularly around battery electric vehicles (BEVs), which tend to be heavier than conventional vehicles and have greater wheel torque, potentially leading to higher tyre particulate emissions.
According to Molden, the impact on tyre wear depends largely on how the vehicle is driven. He notes that BEVs driven gently may produce fewer particles than aggressively driven fossil-fuel cars, although BEVs on still tend to produce slightly more tyre particles on average. That said, BEV’s are expected to become lighter over time.
Conclusion
As we navigate the complex landscape of vehicle emissions, it is clear that the environmental impact of our transportation choices extends beyond the exhaust pipe. Tyre wear, a significant but overlooked source of pollution, poses serious challenges to both human health and environmental integrity.
The revelations about tyre emissions – which dwarf those from the exhaust pipe – demand a reassessment of how we define and regulate ‘clean’ vehicles.
While advances in vehicle technology have successfully reduced exhaust emissions to impressively low levels, the escalating problem of tyre wear from heavier vehicles, especially BEVs, underlines the need for a holistic approach to vehicle pollution. As experts have pointed out, the weight and design of these vehicles can exacerbate tyre emissions, thus potentially offsetting the benefits gained from their zero exhaust emissions.
The road ahead (excuse the pun) should include stringent regulations targeting tyre wear rate and chemical composition of tyres, as well as continued innovation in vehicle design to reduce overall weight. In addition, the promotion of driving practices that minimise tyre wear can also play an important role in reducing this form of pollution.
In conclusion, tackling tyre emissions is not only about improving the sustainability of vehicles but also about protecting public health and safeguarding our ecosystems. By broadening our focus to include non-exhaust emissions, we can make more informed choices that lead to truly cleaner and more sustainable transport solutions.
As we move forward, it is vital that both policymakers and the public remain vigilant and proactive in addressing all sources of vehicle pollution to achieve a greener, healthier future.
