University of Cambridge
Generation, Characterisation and Potential Health Effects of Tyre Wear Particles
Abstract
dc:description.abstractEvery time we drive, as our tyres turn on tarmac, the rubber surface wears away, releasing micro and macroscopic tyre wear particles into our environment. Tyre wear particles are rapidly becoming a significant contributor to urban and suburban air pollution, driven by the move away from internal combustion engines and the implementation of clean air initiatives. Although the total particle concentration in our urban environments is decreasing, we are seeing a shift in the composition of our air toward non-exhaust emissions becoming the dominant traffic-derived particle. While the health effects of exhaust emissions have been studied for many years, the human and environmental health effects of non-exhaust particle emissions from the brakes, tyres and resuspended road wear remain poorly characterised. It has been observed that battery electric vehicles produce more tyre wear in urban and suburban environments than the equivalent combustion vehicle, and forecasts from the United Nations Convention on Long-range Transboundary Air Pollution forecast that by 2050, non-exhaust emissions will constitute up to 90% of all particles from road transport. Tyre wear is not just an air pollution problem; larger particles settle by the roadside and enter water systems. Recent models estimate that nearly 80 kilotonnes of tyre wear enter UK environments per annum, with 4 kilotonnes entering the atmosphere, 28.1 kilotonnes reaching water, and 23.9 kilotonnes depositing in soils. What is lacking is an understanding of the composition of tyre wear particles, both elementally and chemically, to provide adequate information for chemical hazard assessment, and to provide tools to quantify tyre wear in urban atmospheres. Identifying tyre rubber particles in mixed particulate matter samples is a complex challenge due to their chemically complex composition. Tyre rubber is comprised primarily of rubbers, including natural rubber, polyisoprene rubber, butadiene rubber, and styrene-butadiene rubber, vulcanisation agents such as ZnO, as well as trace heavy metals - all of which can leach into the environment through aerosolisation and water run-off, potentially causing long-term health and environmental impacts. This project has developed a comprehensive, multi-element source profile comprising over 70 tyres, the largest sample size of pristine tyre rubber representative of the UK market to date. This profile gives a snapshot of the elemental composition of tyres available on the UK market and has been provided for use in source apportionment calculations. Using untargeted two-dimensional gas chromatography-mass spectrometry, the chemical composition of tyre rubber has been analysed for chemicals of potential environmental concern, aiding in hazard assessment. To aid in classification, chemicals have been assigned chemical taxonomy using the ClassyFire API. The largest challenge in assessing the potential health effects of both micron- and sub-micron tyre wear particles is access to sufficient, well-classified material. The most widely employed solution is to cryo-mill tyre rubber into particles; however, this may change their morphology and thus have an impact on their toxicity. To address this, the first low-cost, benchtop sub-micron tyre wear particle generator has been constructed and validated, capable of generating high concentrations (average of (6.4x10^6#/cm^3) of particles with a mode particle size of 42-62 nm. This device is portable and able to interface with existing in vitro toxicology platforms, such as the VITROCELL® Continuous Flow Exposure Module, making access to reproducible tyre wear nanoparticles free from environmental contaminants more readily available.
Degree
thesis:*- Name dc:type.qualificationname
- Doctor of Philosophy (PhD)
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- University of Cambridge
- Year dc:date.issued
- 2025
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- O'Loughlin, David
- Advisor dc:contributor.advisor
-
- MacFarlane, Marion
Subjects
dc:subject × 5Rights
dc:rightsIdentifiers
dc:identifier.*- Author Identifier
- 0000-0001-5650-1750
- OAI identifier oai:identifier
- oai:www.repository.cam.ac.uk:1810/396861