Characterising Indoor Air Quality in UK Homes: A Population-Based Approach

Indoor air quality is of concern in the public health community given the amount of time people are indoors (~90%) and air pollution more generally is linked to a myriad of health issues. The presence of a variety of VOCs, and the subsequent formation of potentially harmful secondary organic aerosols, are of significant concern. This thesis seeks to elucidate some aspects of this complex area of research. First, observing VOC oxidation in chamber experiments has revealed that a number of SOA intermediates form under a variety of oxidant regimes introduced to the chamber, and that these oxidant regimes greatly impact the rate of decay of the parent compound. Further, differing NOx regimes can have a notable impact, such as on VOC decay, and particle and SOA intermediate formation. Secondly, a number of VOCs are found indoors, however, VOC concentrations cannot be linked to the frequency of use of products in the majority of instances, though covariance analysis reveals some weak but statistically significant relationships. Total VOC concentrations provided some insight into potential exposure indoors. Finally, the reactive potential and the pseudo-first order reactivity of VOCs indoors and major indoor oxidants were assessed. The reaction of n-butane and OH was the reaction with the greatest propensity to form secondary products, and whilst OH was significant in many reactions, the abundance of O3 means it too is a significant oxidant indoors. An indoor chemistry model was used to estimate a variety of key components of indoor air, such as particulate matter and OH concentrations, as well as a novel secondary product creation metric. These components were also measured during a COVID-19 lockdown period in 2020, a proxy for future, low NOx scenarios. Together, the elements of this thesis provide a comprehensive analysis to some of the issues surrounding indoor air quality.