- Objective To evaluate the effects of exposure to air pollution by NOx and SO2 on the development of pulmonary function of children, characterized by different health status. Methods A cohort of 1181 schoolchildren from the 2nd to 5th grades, residing near a major coal-fired power plant in the Hadera district of Israel, were subdivided into three health status groups, according to the diagnosis given by a physician at the beginning of the study period in 1996: (a) healthy children; (b) children experiencing chest symptoms, and (c) children with asthma or spastic bronchitis. Pulmonary Function Tests (PFTs) were performed twice (in 1996 and 1999) and analyzed in conjunction with air pollution estimates at the children's places of residence and several potential confounders—height, age, gender, parental education, passive smoking, housing density, length of residence in the study area and proximity to the main road. Results A significant negative association was found between changes in PFT results and individual exposure estimates to air pollution, controlled for socio-demographic characteristics of children and their living conditions. A sensitivity analysis revealed a decrease in the Forced Expiratory Volume during the First Second (FEV1) of about 19.6% for children with chest symptoms, 11.8% for healthy children, and approximately 7.9% for children diagnosed with asthma. Results of a sensitivity test for the Forced Vital Capacity (FVC) were found to be similar. Conclusion Exposure to air pollution appeared to have had the greatest effect on children with chest symptoms. This phenomenon may be explained by the fact that this untreated symptomatic group might experience the most severe insult on their respiratory system as a result of exposure to ambient air pollution, which is reflected by a considerable reduction in their FEV1 and FVC. Since asthmatic children have lower baseline and slower growth rates, their PFT change may be affected less by exposure to air pollution, reflecting a well known relationship between pulmonary function change and height growth, according to which age-specific height is very similar for preadolescent children, but shifts upward with age during the growth spurt.