Physicochemical characterisation and potential health effects of non-exhaust particle emissions David O’Loughlin 1,2 , Liza Emirali 1 , Molly Haugen 2 , Anne Willis 1 , Adam Boies 2 *, Marion MacFarlane 1 * 1 MRC Toxicology Unit, University of Cambridge, UK, 2 Department of Engineering, University of Cambridge, UK, * Denotes joint senior author. Tyre wear particles (TWP) are an increasing source of ambient particulate matter pollution in the UK and around the world. Currently, TWP accounts for 11% of total particulate matter (PM2.5) in the UK, and over the next 10 years that figure is projected to steadily increase, with UK brake and tyre emissions projected to reach 6 kilotonnes by 2030. Being able to reliably identify and monitor TWP in ambient sources is of increasing importance due to its potential human health effects. The purpose of this study was to identify a characteristic elemental tyre fingerprint that can be utilised in atmospheric source apportionment calculations, and to begin to assess the health effects in vitro . Currently zinc is widely used as a single element tracer to quantify TWP, however several authors have highlighted issues with this approach. To overcome this, tyre rubber tread was digested and has been analysed for 25 elements by ICP-MS to generate a multielement profile. Additionally, to estimate the percentage of the tyre made up of inert fillers, thermogravimetric analysis was performed on a subset. Comparisons were made between passenger car and heavy goods vehicle tyre composition, and a subset of tyres had both tread and sidewall sampled for further comparison. 19 of the 25 elements were detected in the analysis. The mean mass fraction of zinc detected was 11.17 g/kg, consistent with previous estimates of 1% of the tyre mass. Aluminium, iron, and magnesium were found to be the next most abundant elements. Only one source profile for TWP exists in both the US and EU air pollution species profile databases, highlighting the need for more recent data with better coverage of tyre makes and models. This study provides data on new tyres which are currently operating on-road in Europe and is therefore relevant for ongoing atmospheric studies assessing the levels of TWP in urban areas. The results of this work have been published 1 and data have been accepted for inclusion in the upcoming revision of SPECIEUROPE 2 The health effects of tyre wear particles are poorly understood. Previous work has shown that tyre wear have the ability to induce pro-inflammatory and immunogenic responses in the lung, but at doses heavily exceeding representative exposure levels. The focus of this project now moves to understanding the mechanisms and adverse outcome pathways that TWP instigate in the human lung. References 1. O’Loughlin, D.P. et al. (2023) ‘Multi-element Analysis of Tyre Rubber for Metal Tracers’, Environment International , 178, p. 108047. Available at: https://doi.org/10.1016/j.envint.2023.108047. 2. Pernigotti, D., Belis, C.A. and Spanò, L. (2016) ‘SPECIEUROPE: The European data base for PM source profiles’, Atmospheric Pollution Research , 7(2), pp. 307–314. Available at: https://doi.org/10.1016/j.apr.2015.10.007.
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