Does Air Pollution Trigger Infant Mortality in Western Europe? A Case-Crossover Study

Abstract

BACKGROUND: Numerous studies show associations between fine particulate air pollutants [particulate matter with an aerodynamic diameter <= 10 mu m (PM(10))] and mortality in adults. OBJECTIVES: We investigated short-term effects of elevated PM(10) levels on infant mortality in Flanders, Belgium, and studied whether the European Union (EU) limit value protects infants from the air pollution trigger. METHODS: In a case-crossover analysis, we estimated the risk of dying from nontraumatic causes before 1 year of age in relation to outdoor PM(10) concentrations on the day of death. We matched control days on temperature to exclude confounding by variations in daily temperature. RESULTS: During the study period (1998-2006), PM(10) concentration averaged 31.9 +/- 13.8 mu g/m(3). In the entire study population (n = 2,382), the risk of death increased by 4% [95% confidence interval (CI), 0-8%; p = 0.045] for a 10-mu g/m(3) increase in daily mean PM(10). However, this association was significant only for late neonates (2-4 weeks of age; n = 372), in whom the risk of death increased by 11% (95% CI, 1-22%; p = 0.028) per 10-mu g/m(3) increase in PM(10). In this age class, infants were 1.74 (95% CI, 1.18-2.58; p = 0.006) times more likely to die on days with a mean PM(10) above the EU limit value of 50 mu g/m(3) than on days below this cutoff. CONCLUSIONS: Even in an affluent region in Western Europe, where infant mortality is low, days with higher PM air pollution are associated with an increased risk of infant mortality. Assuming causality, the current EU limit value for PM(10), which may be exceeded on 35 days/year, does not prevent PM(10) from triggering mortality in late neonates.