BACKGROUND AND OBJECTIVE: Traffic-related noise and traffic-related air pollution have been associated with cardiovascular disease (CVD). A high ambient correlation between them in traffic conditions may entail that studies investigating the effects of air pollution on CVD are confounded by noise and vice versa. Few studies have investigated this correlation–none in Spain- and results differ among cities. We investigate the contribution of 16 potentially relevant factors such as urban land-use, distance to road or traffic intensity to this correlation in the city of Girona, where a large investigation of chronic effects of air pollution and noise on CVD takes place (REGICOR-AIR).
METHODOLOGY: Nitrogen dioxide (NO2) was used as a surrogate of traffic-related air pollution. Outdoor monthly measurements were conducted with Palmes samplers at 64 locations around Girona in May 2008. All sites were geocoded and an annual traffic noise mean value was derived from a validated noise map (2005; model NMPB routes 96 recommended by the EU). Backward stepwise linear regression models including traffic and land-use markers were fitted both for estimates of annual means of NO2 and for noise.
RESULTS: Noise and air pollution were correlated with r = 0.64 (Pearson). The variables in the models explained 45% of the variability of the NO2 concentrations and 79% of the variability of noise levels. Some determinants related to traffic and street layout differed between NO2 and noise. Common determinants were building density and traffic intensity. These two determinants explained 34% and 59% of the variability of NO2 and noise, respectively.
CONCLUSIONS: Due to the relatively high correlation between noise and NO2, characterization of the two will be very important in our attempts to disentangle the effects of noise and air pollution. We will further evaluate whether correlations differ in different areas of the city or in sub-groups of locations defined by traffic-related factors.
