Emissions of volatile organic compounds from household plastics and their controls: An experimental and modelling approach

Increased consumption and consumer habits over recent decades have led to the accumulation of plastic products within our homes. Although assumed to be chemically inert, these materials can release a multitude of volatile organic compounds (VOCs). Currently, little is understood about VOC emissions from common household plastics, in terms of rates or composition. Consequently, the role that these play within the indoor atmosphere, in terms of secondary product formation, is also relatively unexplored. The aims of this thesis are to quantify emission rates of selected VOCs from common household plastics, determine how they are controlled by abiotic factors such as temperature, sunlight and natural ageing processes, as well as modelling their degradation pathways. Experimental results showed that emission rates of aromatic VOCs, such as benzene, and styrene, increased linearly with temperature, from 0.009-0.03 and 0.02-0.05 ng cm-2 h-1, respectively, between 18 to 28 °C, averaged across all plastic types investigated. UVA light-driven emissions showed a S-shape relationship, with the greatest emission rates between 0.1-1.2 W m-2 0-0.13 and 0-0.025 ng cm-2 h-1, for propene and benzene, respectively. Natural ageing experiments showed high initial VOC emissions between months 1 and 4, which gradually decreased over time, with aromatic compounds showing a 50-90 % reduction in emissions from months 1 to 12. Modelling results show that the diurnal profile of secondary chemical species is driven by the simulated sunlight. The highest impact on the simulated concentrations of ozone and the hydroxyl radical (OH), was produced by the plastic types with the highest overall VOC emissions; the polystyrene-tubing plastic caused an increase in ozone by 1.8 % and a decrease in OH by 15.6 % at 28 °C, in comparison to background simulations without plastics present. This thesis contributes to the understanding of VOC emissions from common household plastics. Evidence from these studies suggests that lowering the presence of plastics indoors can help reduce exposure to harmful VOCs, as well as potentially more harmful secondary pollutants.