Even though electric vehicles remove the problem of fuel emissions, a problem with particulate matter will persist because of tyre wear, warn scientists. More needs to be done to limit the potentially harmful impact of toxic tyre particles on health and the environment, urged researchers from Imperial College London's 'Transition to Zero Pollution' initiative, in their briefing paper, "Tyre wear particles are toxic for us and the environment", published as part of ‘Sustainability Week’ (20-24 February 2023).
Co-author, and vice provost (research and enterprise) at Imperial College London, Professor Mary Ryan, explained that electric vehicles are a "crucial step forward" to decarbonise transport, "but we need to look at the big picture too". She commented that some people are concerned that electric vehicles "tend to be heavier, which might increase tyre wear".
The World Health Organization (WHO) has pointed out that air pollution is one of the "greatest environmental risks to health". It emphasised that by reducing air pollution levels, countries can "reduce the burden" of disease from stroke, heart disease, lung cancer, and both chronic and acute respiratory diseases, including asthma.
The 'Transition to Zero Pollution' initiative brought together a multidisciplinary group of experts – including engineers, ecologists, medics, and air quality analysts to discuss the impacts of tyre wear pollution. In their briefing paper, they outlined current knowledge on the effects of tyre wear particles on health and the environment, the need for a research agenda to build further understanding of the impacts on people and nature, and the essentiality of developing solutions and recommendations for policymakers.
Impact of Tyre Wear Neglected
In the opinion piece, the authors pointed out that six million tonnes of tyre wear particles were released globally each year, and in London alone, 2.6 million vehicles emitted around nine thousand tonnes of tyre wear particles annually.
But the authors criticised that research on the environmental and health impacts of tyre wear had been "neglected" in comparison to the research and innovations dedicated to tackling fuel emissions, and that the effect of new technologies on the generation and impact of tyre wear should be a priority.
Lead author Dr Zhengchu Tan, department of mechanical engineering, Imperial College London, said: "Tyre wear particles pollute the environment, the air we breathe, the water run-off from roads, and has compounding effects on waterways and agriculture. Even if all our vehicles eventually become powered by electricity instead of fossil fuels, we will still have harmful pollution from vehicles because of tyre wear."
The authors explained that: "As tyres break down they release a range of particles, from visible pieces of tyre rubber to nanoparticles." Large particles are carried from the road by rain into rivers, where they may leach toxic chemicals into the environment, whilst smaller particles become airborne and breathed in. "They are small enough to reach into the deep lung," they stressed.
These particles may contain a range of toxic chemicals including polyaromatic hydrocarbons, benzothiazoles, isoprene, and heavy metals like zinc and lead.
Scientists are investigating whether these micro and nano tyre wear particles can enter the bloodstream and/or cross cellular barriers, and what damage these particles and their constituent chemicals have on health, the authors commented.
Every Organ in the Body Can Be Affected
The European Environment Agency highlighted that both short- and long-term exposure to air pollution can lead to a wide range of diseases - including stroke, chronic obstructive pulmonary disease (COPD), trachea, bronchus and lung cancers, aggravated asthma and lower respiratory infections.
The WHO also provided "evidence of links between exposure to air pollution and type 2 diabetes, obesity, systemic inflammation, Alzheimer’s disease and dementia," it said. The International Agency for Research on Cancer has classified air pollution as a "leading cause of cancer".
Chronic exposure can affect "every organ in the body", "complicating and exacerbating existing health conditions," accentuated the EEA.
"The impact of tyre wear particles on human health is an increasing cause for concern, and the full long-term effects on our health urgently require more research," expressed the authors. "There is emerging evidence that tyre wear particles and other particulate matter may contribute to a range of negative health impacts, including heart, lung, developmental, reproductive, and cancer outcomes," they said.
Professor Terry Tetley, National Heart and Lung Institute at Imperial College, and co-author said: "We are growing increasingly concerned by the impact of tyre wear on human health. As some of these particles are so small they can be carried in the air, it’s possible that simply walking on the pavement could expose us to this type of pollution. It is essential that we better understand the effect of these particles on our health."
Co-author Dr Will Pearse, department of life sciences, Imperial College London, said: "Tyre waste does not naturally degrade and instead builds up in the environment, and may interact with other pollutants as well as biological organisms. Our gaps in understanding make further research and development of new solutions vital so we can limit all types of vehicular pollution."
Accelerated Research Tread Needed
In December last year, the Chief Medical Officer, Professor Sir Chris Whitty, urged the Government to make cutting air pollution a priority. He highlighted that air pollution kills between 26,000 and 38,000 people each year in England, and said that the Government needed to "get a grip" on the problem. He repeated these concerns this week when he gave evidence to the Commons Health and Social Care Committee.
In his third annual report Professor Whitty's recommendations on reducing outdoor air pollution included:
- Accelerating the electrification of light vehicles
- Reducing air pollution caused by public transport and heavy and specialised vehicles
- Innovations to reduce air pollution from non-exhaust sources - including particulates emitted from road and tyre abrasion
The research efforts, they said, should include:
- Establishing standardised ways of measuring environmental tyre wear levels and their toxicity
- Reducing harm to land and water species and in humans by tightening limits on the use of harmful components in tyre materials
- Launching new trials to better understand the short and long-term effects of different sized particles on the environment and human health
- Efforts to better understand underlying wear mechanisms and to propose wear mitigation strategies such as reducing vehicle weight, using advanced driving techniques, and ensuring tyre materials pass wear resistance regulations
"We urge policymakers and scientists to embark on ambitious research into tyre wear pollution to fully understand and reduce their impacts on biodiversity and health, as well as research to reduce the generation of these particles," beseeched Dr Tan.