Outdoor air pollution, mortality, and hospital admissions from coronary heart disease in Sheffield, UK: a small-area level ecological study

Abstract

Aims: To examine the hypothesis that coronary heart disease mortality and emergency hospital admission rates are higher in areas with higher outdoor air pollution levels.

Methods and results: Modelled nitrogen oxides (NO(x)), particulate matter (PM(10)), and carbon monoxide (CO) levels were interpolated to 1030 census enumeration districts using an ecological study design. Results, based on 6857 deaths and 11,407 admissions from 1994-98 and a population of 199,682 aged >or=45 years, were adjusted for age, sex, deprivation, and smoking prevalence. Mortality rate ratios were 1.17 (95% CI 1.06-1.29), 1.08 (95% CI 0.96-1.20), and 1.05 (95% CI 0.95-1.16) in the highest relative to the lowest NO(x), PM(10), and CO quintile categories, respectively. Corresponding admission rate ratios were 1.00 (95% CI 0.90-1.10), 1.01 (95% CI 0.90-1.14), and 0.88 (95% CI 0.79-0.98).

Conclusion: The results are consistent with an excess risk of coronary heart disease mortality in areas with high outdoor NO(x), a proxy for traffic-related pollution, but residual confounding cannot be ruled out. If causality were assumed, 6% of coronary heart disease deaths would have been attributable to outdoor NO(x,) and targeting pollution reduction measures at high pollution areas would be an option for coronary mortality prevention.