The joint association of air pollution and noise from road traffic with cardiovascular mortality in a cohort study

Objectives: Associations between cardiovascular mortality and air pollution and noise together were investigated. Methods: Data from the ongoing Netherlands Cohort Study on Diet and Cancer (120 852 subjects; follow-up 1987-1996) were used. Cox proportional hazard analyses were conducted for the association between cardiovascular mortality and exposure to black smoke, traffic intensity on the nearest road and road traffic noise at the home address. Results: The correlations between traffic noise and background black smoke, and traffic intensity on the nearest road were moderate at 0.24 and 0.30, respectively. Traffic intensity was associated with cardiovascular mortality, with highest relative risk (95% confidence interval) for ischaemic heart disease (IHD) mortality being 1.11 (1.03 to 1.20) (increment 10 000 motor vehicles/24 h). Relative risks for black smoke concentrations were elevated for cerebrovascular (1.39 (0.99 to 1.94)) and heart failure mortality (1.75 (1.00 to 3.05)) (increment 10 mu g/m(3)). These associations were insensitive to adjustment for traffic noise. There was an excess of cardiovascular mortality in the highest noise category (> 65 dB(A)), with elevated risks for IHD (1.15 (0.86 to 1.53)) and heart failure mortality (1.99 (1.05 to 3.79)). After adjustment for black smoke and traffic intensity, noise risk reduced to unity for IHD mortality and was slightly reduced for heart failure mortality. Conclusions: Associations between black smoke concentrations and traffic intensity on the nearest road with specific cardiovascular causes of death were not explained by traffic noise in this study.