Correlation between co-exposures to noise and air pollution from traffic sources

Background: Both air and noise pollution associated with motor vehicle traffic have been associated with cardiovascular disease. Similarities in pollution source and health outcome mean that there is potential for noise to confound studies of air pollution and cardiovascular disease, and vice versa, or for more complex interactions to occur. Methods: The correlations between 2-week average roadside concentrations of nitrogen dioxide (NO2) and nitrogen oxides (NOX) and short term average noise levels (Leq,5min) for 103 urban sites with varying traffic, environment and infrastructure characteristics were examined. Results: The Pearson correlation coefficient for Leq,5min and NO2 was 0.53, and for Leq,5min and NOX , 0.64. Factors influencing the degree of correlation were number of lanes on the closest road, number of cars or trucks during noise sampling and presence of a major intersection. Conclusions: We recommend measurement of both pollutants in future studies of traffic-related pollution and cardiovascular disease to allow for more sophisticated analysis of this relationship.