Prevalence of children's allergic diseases in Ulsan: Local differences and environmental risk factors

This study aims to investigate the AD (asthma, allergic rhinitis and atopic dermatitis) prevalence for elementary schoolchildren in an industrial city of Ulsan, Korea and to identify major environmental risk factors associated with AD prevalence. Data on the physician-diagnosed prevalence in the past 12 months and potential risk factors of AD were collected by a questionnaire including ISAAC core questions from the 2009-2010 survey of 4,067 schoolchildren (1st-6th grade) living in different urban environments. Exposure to outdoor air pollution was estimated by using annual mean concentrations of pollutants (PM10, O3, NO2, SO2 and CO) obtained from monitoring sites near the participant's residence. Our survey results showed that the AD prevalence rate ranged between 26.2% and 35.9%. Children living in polluted areas (near industrial and central urban areas) had about 10% higher prevalence of AD than those living in coastal or suburban residences. The Chi-Square test demonstrated that this local difference was statistically significant before and after adjustment of major confounder such as parental AD history and parental education. The results of the logistic regression analysis showed that current AD prevalence was significantly associated independently with socio-economic indices and indoor/outdoor environmental factors. Statistically significant association between several environmental factors (ventilation in winter, odor condition and exposure to traffic smoke, and outdoor PM10/O3 pollution) and the prevalence of AD was found by multivariate model after adjusting confounders. The adjusted odd ratios for the AD prevalence were 1.24 (95% CI: 1.03-1.49) and 1.79 (95% CI: 1.17-2.75) with increase in PM10 level of 10 μg m-3 and O3 level of 10 ppb, respectively. Although there should be other risk factors for AD, these results suggest that living in polluted area and exposure to high levels of air pollutants can contribute to the increased risk of childhood AD.