Short-term effects of air pollution on mortality in the cities of Rouen and Le Havre, France, 1990-1995

In this study, the authors examined the short-term effects of ambient air p ollution on mortality across 2 French cities: Rouen and Le Havre. In Poisso n regression models, which controlled for day-of-week effects, the authors used nonparametric smoothing to control for temporal trend, weather, and in fluenza epidemics. In Rouen, an interquartile range increase of 60.5-94.1 m ug/m(3) of ozone was associated with an increase of 4.1% (95% confidence in terval = 0.6, 7.8) of total mortality. Daily variations in sulfur dioxide ( interquartile range increase = 17.6-36.4 mug/m(3)) were also associated wit h an 8.2% increase (95% confidence interval = 0.4, 16.6) in respiratory mor tality. An increase of 6.1% (95% confidence interval = 1.5, 10.9) of cardio vascular mortality was also observed with an interquartile range increase o f nitrogen dioxide (i.e., 25.3-42.2 mug/m(3)). With respect to Le Havre, an interquartile range increase in daily levels of sulfur dioxide (11.3-35.6 mug/m(3)) was associated with an increase of approximately 3% (95% confiden ce interval = 0.8, 5) of cardiovascular mortality. For particulate matter l ess than or equal to 13 mum in diameter (interquartile increase = 21.5, 45. 4 mug/m(3)), an increase of 6.2% (95% confidence interval = 0.1, 12.8) was observed. The estimates of pollutant effects and their standard deviations were slightly affected by the degree of smoothing temporal variations in th is study. When low collinearity was present, the 2-pollutant models provide d acceptable estimates of pollutant effects. They suggested that the ozone effect was independent of the Black Smoke effect, and that the effects of s ulfur dioxide and nitrogen dioxide were unlikely to be confounded by ozone concentrations. However, high collinearity leads to large estimates of the pollutant coefficient variances and, therefore, leads to inaccurate estimat es of pollutant effects. The analysis of the contributory effects of differ ent pollutant mixtures requires further investigation in those instances in which high collinearity between pollutants is present.