This MD thesis explores the relationship between air and public health from early civilisations to the present day. Through examination of the changing relationships the thesis aims to identify, and critically explore, contemporary problems in public health theory and practice. This is a thesis primarily in the history of medicine or, more specifically, the history of public health. The thesis adopts an accepted five-stage framework for historical research. Within the framework, the thesis utilises two further, well established aspects of historical enquiry. First, it addresses the research questions by using historical case studies. Secondly, the historical research incorporates inter-disciplinary components, in particular the inclusion of ethics. The first case study initially explores air and health in ancient civilisations, especially within Greek medicine and philosophy, and then examines connections and relationships with ideas about air and health in mid-nineteenth century Britain. The second case study traces the changing relationship between air and public health from the mid-nineteenth century until about 1970, through examining developments in smoke pollution policy and scientific understanding of the effects of smoke on health. The third case study covers a period of three decades up to the present day. A piece of air pollution epidemiological research called quantitative risk assessment (QRA) is used as a vehicle through which to investigate philosophical, ethical and policy considerations in contemporary public health theory and practice. The fourth case study explores the approach to dealing with climate change. The approach is used as an instrument to probe utilitarianism as the moral foundation of public health, to explore other ethical frameworks, and to examine the relevance for environmental work within public health. Conclusions from each case study are drawn, and analysis of the links between the four case studies provides recommendations for public health theory and practice.