Asthma and factory emissions in northern England: addressing public concern by combining geographical and epidemiological methods.

STUDY OBJECTIVE--The prevalence of asthma was assessed to investigate respiratory health effects of airborne emissions from a factory. A geographical information system allowed flexible definition of study areas in terms of their size, distance, and location in relation to the factory. The value of the approach for this type of investigation is focussed on. SETTING--The factory is located in the south western part of a small market town in County Durham. MEASUREMENTS AND MAIN RESULTS--A total of 1573 asthma cases were identified from general practitioner computerised repeat prescribing systems. Population denominators were defined from family health services authority patient registers. The area within 1 km and immediately to the north east of the factory had an age and sex standardised asthma prevalence 24% (confidence interval 4, 44%) in excess of the expected rate (p = 0.01). The increased prevalence was confined to middle aged and elderly adults living in the area between 0.5 and 1 km to the north east of the factory. CONCLUSIONS--The value of combining the skills of geographers and epidemiologists in addressing public health issues is shown, particularly through the use of geographical information systems which proved powerful and effective.