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Table 3 Descriptive characteristics of the subjects and the prevalence of respiratory symptoms based on the questionnaire

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

Residential area

Apartment

Ger dwelling

Total

District

A urban

B urban

C urban

D suburban

 

n

%

n

%

n

%

n

%

n

%

Response rate

238

79

273

91

300

100

298

99

1109

92.4

Sex

  Female

129

54

123

45

122

41

141

47

594

53.6

  Male

109

46

150

55

178

59

157

53

515

46.4

Age

  6–8 years

135

57

161

59

146

49

176

59

618

55.7

  9–12 years

103

43

112

41

154

51

122

41

491

44.3

Feeding in infancy (bottle milk)

52

22

47

17

57

19

48

16

204

18.4

History of respiratory diseases before 2 years old

68

29

89

33

65

22

66

22

288

26.0

History of diagnosed asthma

12

5.0

2

0.7

6

2.0

7

2.3

27

2.4

History of allergic diseases

52

22

57

21

38

12

29

10

176

15.9

History of pneumonia

16

7

25

9

16

5

12

4

69

6.2

Parental smoking habit at home

87

37

103

38

146

49

142

48

478

43.1

History of residence years

150

63

170

62

187

62

220

74

727

65.6

Heating type (coal using)

6

3

11

4

141

47

214

72

372

33.5

Distance from major road < 100 m

119

50

126

46

99

33

69

23

413

37.4

Daily traffic volume

16,842

16,985

19,473

7187

60,487

Respiratory symptoms

 

Persistent cough

60

25

50

18

95

32

111

37

316

28.5

Persistent phlegm

50

21

50

18

63

21

61

21

224

20.2

Asthma-like symptom

4

2

0

0

2

1

2

1

8

0.7

Current wheezing

22

9

14

5

17

6

11

4

64

5.8