Coal burning-derived SO2 and traffic-derived NO2 are associated with persistent cough and current wheezing symptoms among schoolchildren in Ulaanbaatar, Mongolia

Table 4 The association between outdoor SO₂ and NO₂ concentrations and prevalence of respiratory symptoms among schoolchildren in the questionnaire survey using a logistic model, adjusted for confounding variables (n = 1109)

	OR for absolute increase of per 1 ppb in air pollutants
Respiratory symptoms	SO₂	NO₂
Persistent cough	1.12 (1.04–1.22)	1.14 (0.97–1.34)
Persistent phlegm	1.03 (0.94–1.12)	1.07 (0.91–1.27)
Current wheezing	1.06 (0.91–1.24)	1.33 (1.01–1.75)

Data are presented as OR—odds ratio (95% CI confidence interval)
Confounding variables: gender, age, history residence year, history of asthma and allergies, history of respiratory diseases before 2 years old, history of pneumonia, feeding method in infancy, parental smoking habits, heating type, distance from the major road
Mean concentrations for outdoor SO₂ of each district 5.2 ppb, 4.4 ppb, 10.1 ppb, and 7.1 ppb, for NO_2—30.0 ppb, 27.7 ppb, 30.0 ppb, and 18.2 ppb, respectively. And traffic volume was calculated as a value per thousand vehicles a day of each district: 16.84, 16.99, 19.47, and 7.19, respectively
Values in bold indicate statistical significant: p < 0.05

ISSN: 1347-4715