Respiratory Health in a Changing World: The Role of Pollen and its Interaction with Greenspace on Childhood Lung Function

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Psychology and Public Health, College of Science, Health and Engineering, La Trobe University, Victoria, Australia.

We live in a world with rapidly increasing urbanisation and changes to global climate impacting pollen production and allergenicity. Pollen exposure plays a role in emergency department presentations and hospitalisations for asthma, but there is little exploration of its effect on lung function and airway inflammation. This thesis by publication explores the long term and acute associations of pollen with lung function and airway inflammation, and potentially interactive effects of residential greenness. Two systematic reviews explore the effect of greenspace on allergic diseases. Three original research articles use daily ambient pollen concentrations, measured in four regions of Australia and Germany, and residential greenness calculated by NDVI. Lung function was measured by spirometry in four cohorts and fractional exhaled nitric oxide (FeNO) was available from three cohorts. Exposure to grass pollen in early life was consistently associated with decreased lung function in children and adolescents. Reductions were stronger for forced vital capacity (FVC), than forced expiratory volume (FEV1) while the ratio was unchanged or even increased. This restrictive pattern suggests a potential global reduction in lung function. In the German cohorts, higher levels of ambient birch pollen between five to seven days before testing were associated with reduced FEV1 in those children sensitised to birch pollen, with weaker associations for FVC. Acute grass pollen exposure was associated with increased FeNO levels in all children and living in an area with higher NDVI significantly enhanced this association. In Sydney, Casuarina and Pinus pollen were associated with reduced lung function. While further studies are required to determine the mechanisms behind these associations, grass pollen avoidance strategies for infants may be of benefit. Pollen-sensitised individuals and those with asthma should be made aware of available pollen forecasts and the possible influence of pollen exposure on the respiratory system up to a week after exposure.