| Risk Assessment of Environmentally Influenced Airway Diseases Based on Time-Series Analysis
Olf Herbarth Department of Human Exposure Research and Epidemiology, Centre for Environmental Research Leipzig-Halle, 04301 Leipzig, Germany Abstract
Threshold values are of prime importance in providing a sound basis for public health decisions. A key issue is determining threshold or maximum exposure values for pollutants and assessing their potential health risks. Environmental epidemiology could be instrumental in assessing these levels, especially since the assessment of ambient exposures involves relatively low concentrations of pollutants. This paper presents a statistical method that allows the determination of threshold values as well as the assessment of the associated risk using a retrospective, longitudinal study design with a prospective follow-up. Morbidity data were analyzed using the Fourier method, a time-series analysis that is based on the assumption of a high temporal resolution of the data. This method eliminates time-dependent responses like temporal inhomogeneity and pseudocorrelation. The frequency of calls for respiratory distress conditions to the regional Mobile Medical Emergency Service (MMES) in the city of Leipzig were investigated. The entire population of Leipzig served as a pool for data collection. In addition to the collection of morbidity data, air pollution measurements were taken every 30 min for the entire study period using sulfur dioxide as the regional indicator variable. This approach allowed the calculation of a dose-response curve for respiratory diseases and air pollution indices in children and adults. Significantly higher morbidities were observed above a 24-hr mean value of 0.6 mg SO 2 /m 3 air for children and 0.8 mg SO 2 /m 3 for adults. Using the derived threshold value, the attributable risk for respiratory disease for children exposed to an increase, for example, from 0.6 to 1.2 mg SO 2 /m 3 air (24-hr mean) (i.e., a doubling of the threshold level) was 30/10,000. For adults this risk was 2/10,000. Key words : airway diseases, epidemiology, risk assessment, threshold value, time-series analysis. Environ Health Perspect 103:852-856 (1995)
Address correspondence to O. Herbarth, Department of Human Exposure Research and Epidemiology, Centre for Environmental Research Leipzig-Halle, PO Box 2, 04301 Leipzig, Germany. Received 4 October 1994 ; accepted 14 June 1994.
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