As traffic-related air pollution and traffic noise share road traffic
as a source, it is necessary to mutually adjust for these two factors
when exploring their effects on BP. The potential confounding relationship
between traffic-related air pollution and noise has been
previously highlighted (Allen and Adar, 2011), but only two studies
(Bilenko et al., 2013; Clark et al., 2012) have examined this issue
among children. Bilenko et al. (2013) reported a positive association
between childhood BP and long-term NO2, and no association with
noise. Clark et al. (2012) found no statistical associations between
NO2 and childhood BP before and after adjusting for road-traffic
noise at school.