Linking Particulate Matter Oxidative Potential to Atmospheric Conditions and Particle Composition

Air pollution exposure is a major global health issue; 99% of the world's population in 2019 lived in places where air quality standards exceed recent guideline limits set by the world health organisation (WHO), and is attributed to over 7 million premature deaths per year. The WHO recently reduced air quality guideline limits for exposure to airborne particulate matter less than 2.5 um in diameter (PM2.5) from 10 ug m-3 to 5 ug m-3 annual mean exposure, as PM is the most toxic component of air pollution and a major global health burden. Despite compelling evidence specifically linking exposure to particulate matter (PM) with adverse health effects, the health-relevant chemical components of PM, and the mechanisms by which they induce toxicity upon exposure, remain highly uncertain. Recent studies have widely suggested that PM oxidative potential (OP), a biologically relevant chemical metric describing intrinsic PM toxicity, is key to determining the health effects of PM exposure. However, accurate quantification of OP has been hindered by lack of suitable measurement methods, as many chemical components contributing to OP are short-lived and in low ambient concentrations, posing a significant analytical-chemical challenge. Current policy seeks to abate all sources of PM to reduce health impacts; this is not a cost-effective and is an inefficient approach to reducing the health burden of PM exposure. Thus, OP has the potential to quantify the drivers and specific sources that are responsible for observed health effects, which is crucial for governments to efficiently respond to recent WHO policy changes. However, robust and accurate quantification is essential to determine the sources, atmospheric drivers and health-outcomes related to OP exposure. My project represents the first application of a novel instrument that I developed during my PhD and post-doctoral career. The Online Oxidative Potential Ascorbic Acid Instrument (OOPAAI) can quantify PM OP in situ with a time resolution of 10 minutes, providing vastly improved quantification of PM OP by providing more robust and accurate OP measurement, eliminating measurement artefacts as a result of offline analysis, and providing highly time resolved data thus capturing OP changes on atmospherically relevant timescales. This method will be deployed in laboratory studies, probing fundamental chemical drivers of PM OP and ambient field campaigns alongside ongoing established atmospheric pollution measurements, mapping the temporal and spatial variability of OP across several different environments in the UK. This project will substantially improve our understanding of the physical and chemical atmospheric components influencing OP. Furthermore, it will help clarify the different contexts within which PM OP is most prevalent at a time when the contributors to ambient PM concentrations are changing due to local, national and international emission abatement policies. The outputs of this project will provide vital evidence linking sources to intrinsic PM toxicity, and establish a novel method for reproducible, robust and long- term measurements which are essential in order to correlate PM OP with health outcomes in future epidemiological studies.