Asthma and Plants: Chemotaxonomic Relationships and Patterns of Asthma Incidence and Respiratory Symptoms, in Urban Coastal Versus Rural Highland Areas in South-East Queensland, Australia, with Special Reference to the Family Myrtaceae
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This thesis represents an exploratory and iterative study into the relationships of Australian native plants from the family Myrtaceae, with respiratory symptoms, specifically asthma. This relationship is explored from a chemo-taxonomic stance and the connections with other plants with related chemotaxonomy are underlined. The research was performed against a background of geographical comparison between an urban coastal area and a rural mountainous area 90 kilometres just north of Brisbane, Queensland, Australia. The focus was the possible contribution of Melaleuca quinquenervia to the occurrence of autumn respiratory symptoms, especially asthma. The research challenges current beliefs that wind-pollinated plants are the only sources of allergens and the major botanical health threat for those who suffer with asthma. There is some critical analysis of the current understanding of world patterns of asthma, with particular reference to the Global Initiative for Asthma (GINA) geographic compilations. In this study 380 children were skin-tested with a battery of commercial allergens including Eucalyptus. Comparisons among children from three coastal schools and students from one mountain school were made with a view to testing the hypothesis that proximate vegetation would affect responses to allergens. As hypothesised, significant differences were detected between the coastal and range students in responses to Eucalyptus, which flowers prolifically on the coast. Coastal children, compared to the rural children from the mountain area exhibited a significantly greater percentage of skin-test responses (p≤.05) to Eucalyptus, when all responses greater than zero were measured. In the next phase more comparisons were undertaken with a smaller group of adults and adolescents in the coast and range communities. A range of terpenes and oxidized terpenes was applied during skin tests along with commercial allergens. Coastal and range reaction profiles revealed that coastal participants exhibit greater skin reactivity. When a 3mm wheal cut-off is employed alpha-pinene response in the range group is notable. During this second phase ambient air sampling was carried out at the same time as participants measured peak expiratory flow (PEF) and recorded respiratory symptoms. Chemicals trapped on Tenax over spring and autumn were analysed via GCMS and the results combined with symptom variables to ascertain significant predictors of symptom change. Using stepwise and general linear regression significant relationships were demonstrated between PEF and beta pinene and limonene in ambient air. In both types of modelling several terpenes were shown to be significant predictors of respiratory symptoms. In the coastal group the addition of alpha or beta pinene to a General Linear Regression model predicting standardized peak flow, accounted to an additional 20% of the variance in autumn. The model consisted of ozone, nitrogen dioxide and particulates less than 10 micron, all lagged three days. For spring, the additional variance explained was only 6 % and for spring an autumn combined it was 5%. Significant relationships were also demonstrated between linalool levels and preventer and reliever usage. The results support the hypotheses regarding the role of terpenes as having a possible role in the acquisition and exacerbation of asthma. Additionally a number of floral studies resulted in chemical profiles being elucidated for flowers from popular plants in Australia. Tenax collections of vapours from some household and lifestyle products resulted in chemical profiles for popular items. In conclusion, some observations about vegetation and patterns of asthma have been made and a new model of asthma acquisition proposed.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Public Health
Item Access Status
Pages vi-x were replaced by pages from the first edition.
Native vegetation and asthma