Establishing links between air quality and health: searching for the impossible?

Traditional approaches in environmental spatial epidemiology have relied on assessing postulated links between environmental pollution and ill health, often as a response to a perceived public health problem; clearly it may be necessary to go beyond this stage in order to establish the nature of potential causal mechanisms. Different disciplines approach this issue in different ways. Many toxicologists favour approaches based on air quality monitoring, where raised levels of candidate pollutants may subsequently generate hypotheses about adverse health effects. Epidemiologists, however, assess the health of a population and then look for an associated cause. This paper suggests that neither approach is completely satisfactory and that a combination of both is needed. If spatially referenced data are available for both health status and air quality, then geographical analysis is needed to examine possible links, by using techniques such as atmospheric dispersion modelling and Geographical Information Systems. We discuss the benefits and constraints of these approaches, using empirical examples of environmental epidemiology studies for northern England. Taking into account the problems involved in such studies, allied to the high costs incorporated, the paper asks the question: Are we searching for the impossible?