38 Physicochemical Characterisation and Potential Health Effects of Tyre Wear Particles

Abstract

Tyre wear is an increasing source of ambient particulate matter pollution in the UK and around the world. Currently, tyre wear 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 tyre wear PM in ambient sources is of increasing importance due to its potential human health effects. Here we present a series of characterisation experiments on tyre particles, size-fractionated using a dynamometer. Chemical and elemental composition has been determined by inductively coupled plasma mass spectrometry (ICP-MS) and two dimensional gas chromatography time of flight mass spectrometry (GCxGC-TOF-MS), with particle morphology studied using a scanning electron microscope and energy dispersive spectroscopy (SEM-EDS) and an electrical low pressure impactor (ELPI). The potential health effects of these particles have then been assessed in vitro using human bronchial epithelial cells following the IARC characteristics of carcinogenicity, specifically looking at (pro)inflammatory cytokines, cytotoxicity and mitochondrial function. Tyre wear particles have the ability to reduce mitochondrial function significantly from doses as low as 5μg/ml after 24 hours, with the induction of cytokines and chemokines currently being profiled. Additionally, a representative elemental and chemical fingerprint of tyre rubber has now been established. By understanding the composition and morphology of these particles, we can begin to detect them in atmospheric samples, and using in vitro models, understand their potential health effects.