Determinants of Oxidative Potential, A Health-Based Metric to Assess Particulate Matter Toxicity

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Particles which are so small as to be invisible to the naked eye are very abundant in the atmosphere. They come from a wide range of sources (e.g. road traffic) and are diverse in terms of their particle sizes and chemical composition. Earlier epidemiological studies have shown clearly that exposure to airborne particles has an impact on human health with more deaths and hospital admissions for respiratory and cardiovascular diseases on high pollution days and those immediately following. However, to date the epidemiology has focussed very largely on the mass of particles in wide size ranges known as PM2.5 and PM10 and has not discovered whether particular properties of the particle such as their size or chemical composition determine the relative toxicity. There would be great benefit in doing so as abatement strategies could then focus on the sources emitting the most toxic particles. In this project it is proposed to collect large samples of airborne particles in different size fractions including the ultrafine fraction (of less than 100 nanometres diameter) which is believed to have a higher toxicity per unit mass. The samples of particles will be subjected to detailed chemical analysis in the laboratory as well as being tested for their ability to exert oxidative potential, in other words, to consume the body's anti-oxidant defences. The overall aim is to understand which properties of the particles have the greatest influence on their oxidative potential which could then inform the design of epidemiological studies to investigate the links between those particle properties and effects on human health.