The impact of ambient particulate matter exposure on adult respiratory health in southeastern Australia.

This thesis examines the impact of ambient particulate matter (PM) on respiratory symptoms in Australian adults. Respiratory symptoms are often overlooked in epidemiological studies on PM, yet they represent the activation of inflammatory physiological responses by inhaled particles. It is hypothesised that respiratory symptoms represent the most common adverse health impact of PM on healthy individuals. It is expected that proportionally fewer individuals are adversely affected as the severity of the health impact increases, so that relatively few people require emergency treatment, hospitalisation or end up dying as a result of PM exposure. Respiratory symptoms may often be mild and transient, but chronic and/or severe symptoms can have a substantial detrimental impact on quality of life, including the ability to work and take part in recreational activities. Respiratory symptoms also represent exacerbations of underlying chronic diseases such as asthma, which may be life-threatening, as well as requiring medical care, medication use and resulting in sub-optimal disease management. This thesis addresses the current lack of knowledge on associations between ambient PM and respiratory symptoms in Australian adults. The first study examined cross-sectional and longitudinal changes in respiratory symptoms in adults in Melbourne (Victoria). There was little evidence to suggest that PM2.5 in Melbourne poses a substantial health threat to most adults. The next studies examined respiratory symptoms in participants in the 2004 Tasmanian Longitudinal Health Study (TAHS). An ecological study examined symptoms reported by TAHS participants in Launceston and Hobart (Tasmania). Air quality in Launceston is severely degraded by wood smoke-derived PM10 during the winter months, whereas air quality in Hobart is much better. The results did not provide convincing evidence that respiratory symptoms were associated with wood smoke-derived PM10 in Launceston, although it is likely that the small sample size affected the results. Variations in air quality within Launceston were then examined using The Air Pollution Model (TAPM) to estimate, and Geographic Information Systems (GIS) to map, PM10 concentrations. There was little evidence to suggest that respiratory symptoms or symptom scores were associated with spatial variations in PM1O. Further analyses suggested that the small city size and confounding by vehicle traffic may have overshadowed any associations with ambient PM 10. The results of this thesis suggest that ambient PM concentrations in Melbourne and Launceston may currently be low enough to pose little threat to the respiratory health of most adults. However, the scientific evidence strongly suggests ambient PM exposure does have an adverse impact on adult respiratory health. The small study sample sizes and low exposure variation between study participants likely reduced the ability of these studies to detect any significant associations between respiratory symptoms and ambient PM in these cities.