Evolution of Reactive Oxygen Species on Particles in the Roadside Environment

Particles are a key driver of health effects in urban air. In Hong Kong, the crowdedurban environment makes it likely that people receive a significant burden fromparticles that are generated by road vehicles. These particles are extremely small in sizeand although regulated it has been assumed that all particles of a given size are equallytoxic. The composition of particles is both variable and complex, so it is not easy toanalyse particles in an attempt to identify the components that affect urban health.Increasingly health impact has been related to those compounds that can induceoxidative stress in the lung, especially through the production the superoxide radical(˙O2-), the hydroxyl radical (˙OH) and hydrogen peroxide H2O2). Such reactiveoxygen specials can be estimated from chemical reactions in extracts from collectedparticles.Reactive oxygen species have been found to be concentrated on particles near theroadside and other urban environments, but also at higher concentrations in thesummer. They also appear to be produced in particles containing copper. The proposedresearch will examine the potential for reactive oxygen species to form on airborneparticles as they are transported away from the roadside in Hong Kong, by collection andanalysing these at various distances from the roadway. Laboratory experiments willattempt to see if ozone or light can alter the concentration of reactive oxygen species onparticles. Additional experiments will determine the distribution of reactive oxygenspecies in a number of sitting out areas as these are locations where elderly people(often the most sensitive to particulate air pollution) spend their days at locations thatare frequently close to busy roads.The current project is novel not simply because it looks at reactive oxygen species at theroadside in Hong Kong and considers unique Hong Kong environments such as sittingout areas, but it attempts to examine transformations that might influence particletoxicity. It will hopefully encourage thought to be given to particle toxicity when framingair pollution legislation. Additionally it might help shift air pollution control in HongKong away from a focus on reducing emissions to a broader consideration how we mightreduce our exposure to the most harmful air pollutants.