Respiratory symptoms, asthma and levels of fractional exhaled nitric oxide in schoolchildren in the industrial areas of Estonia

Abstract

ObjectivesExposure to air pollutants in the ambient environment has been associated with various respiratory symptoms, and with increased asthma diagnosis, in both children and adults. Most research to date has focussed on core pollutants, such as PM10, PM2.5, SO2 and NO2, and less attention has been given to the effects of industry-specific contamination. The current study aimed to examine the associations between respiratory symptoms, asthma, increased levels of fractional exhaled nitric oxide (FeNO) (as a marker of eosinophilic airway inflammation) and ambient levels of industrial pollutants (such as benzene, phenol, formaldehyde and non-methane hydrocarbons) for schoolchildren living near oil shale industries in Ida-Viru County, Estonia. MethodsA total of 1326 schoolchildren from Ida-Viru, Lääne-Viru and Tartu Counties participated in a cross-sectional study, consisting of questionnaires on respiratory symptoms and asthma, as well as clinical examinations to measure FeNO. Dispersion modelling was used to characterize individual-level exposure to industrial air pollutants at each subject's home address. Associations between exposure and respiratory health were investigated using logistic regression analysis, and differences in results between regions were analysed using the Chi-squared test. ResultsThe prevalence of respiratory symptoms (p < 0.05) in children living near (i.e. within 5 km) of an oil shale industry site in Ida-Viru County was 2–4 times higher than in children living in the reference area of Tartu County. Children exposed to 1 μg/m3 higher levels of benzene and formaldehyde had a higher odds ratio (OR) of having rhinitis without a cold (OR 1.03, 95% confidence interval (CI) 1.01–1.06), of ever having had attacks of asthma (OR 1.05, 95% CI 1.01–1.10) and of having a dry cough a few days per year (OR 1.05, 95% CI 1.01–1.10). Children exposed to 1 μg/m3 higher levels of benzene, formaldehyde, phenol and non-methane hydrocarbons had a higher odds ratio of having high FeNO levels (≥30 ppb): OR and 95% CI of 1.05, 1.01–1.09; 1.22, 1.06–1.41; 1.01, 1.00–1.01; and 1.75, 1.75–2.62, respectively.