Introduction Several reviews on the effects of air pollution (Brook and Rajagopalan, 2009; Brook et al., 2011; Brunekreef and Holgate,2002) and road-traffic noise (van Kempen and Babisch, 2012) on blood pressure (BP) have concluded that exposure to air pollution and/or traffic noise causes increase of BP. Most previous studies have been on adults or the elderly, while less has focused on children. As childhood BP is a strong predictor for hypertension later in life (Lauer et al., 1991), understanding the factors that influence childhood BP is important.