Low frequency noise and stress: bronchitis and cortisol in children exposed chronically to traffic noise and exhaust fumes.

A correlation of respiratory diseases to traffic related air pollution and noise was observed in an interview study. Since in that study the exposure was subjectively assessed, in the present field study nitrogen dioxide as indicator for vehicle exhausts and the mean night-time noise level were measured outside the children's windows in representative locations. Based on these measurements each child was placed in one of the following categories: low, medium or high traffic immission (ambient emissions). The physician contacts due to bronchitis of 68 children were assessed retrospectively from the files of the participating paediatricians. Saliva samples were collected from all children and the cortisol concentration was estimated. Children under high noise exposure (L(night, 8h) = 54-70dB(A)) had in comparison to all other children significantly increased morning saliva cortisol concentrations, indicating an activation of the hypothalamus-pituitary-adrenal (HPA) axis. Analysing a subgroup of children without high noise exposure showed, that children with frequent physician contacts due to bronchitis did not have increased morning saliva cortisol. However, multiple regression analysis with stepwise exclusion of variables showed that bronchitis was correlated more closely to morning salvia cortisol than to traffic immissions. On the other hand, the rate of physician contacts due to bronchitis increased in a dose dependent manner and significantly with increasing traffic immissions. From these results it can be concluded that high exposure to traffic noise, especially at nighttime, activates the HPA axis and this leads in the long term to an aggravation of bronchitis in children. This seems to be more important than the effect of exhaust fumes on bronchitis symptoms. The results of the present study should be subjected to further investigation using specially designed studies.

Respiratory and dermatological diseases in children with long-term exposure to road traffic immissions.

The pathogenesis of allergies can be stimulated by adjuvant effects--i.e. air pollutants such as NO(2) and particles from diesel exhausts as well as noise--the latter especially during night-time. During sleep, noise signals which are associated with danger (i.e. lorry noise) have the potential to trigger stress reactions even if the noise level is low. Increases of cortisol in the first half of the night seem to play an important role. In a blind interview study, the combined effects of chronic exposure to traffic related air pollution and noise, upon the risk of skin and respiratory diseases in children were studied. All children between 5-12 years, who had consulted one of two participating paediatricians were included in the study. The paediatricians diagnoses of 400 children were analysed together with their parents answers regarding the density of road traffic on their street and several confounding factors. Multiple regression analyses resulted in relative risks of asthma, chronic bronchitis and neurodermitis, which increased significantly with increasing traffic load. A comparison with the literature on such effects caused by air pollution alone, showed that traffic noise during the night might have an adjuvant effect on the pathogenesis of the mentioned diseases.