Int. J. Environ. Res. Public Health 2010, 7 3459 habituation to noise and sensitization to non-noise stressors might be indicative of dysregulation of the stress response system. Similarly, a pattern of diminished response to both noise and non-noise stressors might be indicative of dysregulation of the stress response system. Impairment of blood pressure responses resulting from iterative stress exposures may reflect damage to normal, healthy physiological stress-response systems that are designed to mobilize energy to support coping efforts when an acute environmental demand is encountered [19-21]. We could find only one study on the relation between chronic noise exposure and blood pressure reactivity. In that study, children in a noisy community near a major airport had lower SBP reactivity in response to an acute stressor, which consisted of intermittent noise (80 dBA peaks) while reading a text, than did their counterparts in a quieter community [22]. There was no relation between noise exposure and DBP reactivity. This study provides some evidence that children in the noisy schools habituated to noise. However, because there was no assessment of reactivity to non-noise stressors, it is not clear if there were other adaptive costs of noise exposure, such as sensitization to non-noise stressors or possible diminished arousal in response to varied stressors. The present study was designed to characterize these distinct patterns of relations between chronic noise exposure and reactivity. In summary, the present study adds to the literature on the association between chronic exposure to community noise and levels of resting blood pressure in children. The study also examines whether chronic noise exposure compromises children’s stress response systems, by examining the relations between chronic noise exposure and blood pressure responses during exposure to acute stressors similar to the chronic stressor (acute noise) and a novel psychosocial stressor (mental arithmetic). A novel contribution of the study is that it examines the relations between chronic noise exposure and children’s blood pressure reactivity during acute exposure to both noise and non-noise stressors. The resulting data could reveal a variety of patterns, including a potentially adaptive pattern, in which children selectively habituate to noise stressors but respond normally to non-noise stressors, or a potentially maladaptive pattern, in which children habituate to noise stressors but are hyper- or hypo-reactive to non-noise stressors. 2. Methods 2.1. Setting Participants were drawn from two public schools in Pune, India, the eighth largest city in India, with a population of over 3.7 million people [23]. The ―noisy‖ school selected for this study was located in a busy commercial district on a street with much traffic noise. Traffic noise is probably the most pervasive type of chronic noise exposure for children, especially in India [24]. The ―quiet‖ school was located in a less commercial area of the city and offset from the street by at least 100 yards. The buildings of the two schools are of similar construction and have classrooms with open-air windows, so outside ambient noise easily drifts into the buildings. Noise levels at both schools were measured mid-morning between the outside entrance to the buildings and the school gate. Over a 5-minute interval, noise levels at the noisy school reached a peak of 82 dB(A) and at the quiet school reached a peak of 65 dB(A).