Table 1

Demographic characteristics of the study participants

Characteristics	n	%
Respiratory symptoms
No	3098	86.7
Yes	477	13.3
SHS exposure in general
No	1101	30.8
Yes	2474	69.2
SHS exposure in indoor public places
No	1806	50.5
Yes	1769	49.5
SHS exposure in homes
No	2342	65.5
Yes	1233	34.5
SHS exposure in indoor campuses
No	2763	77.3
Yes	812	22.7
SHS exposure in outdoor campuses
No	2532	70.8
Yes	1043	29.2
Asthma history
No	3514	98.3
Yes	61	1.7
Grade
1–2	2329	65.2
4–5	1246	34.8
Only child
No	1353	37.8
Yes	2222	62.2
Gender
Male	1818	50.9
Female	1757	49.1
Pocket money monthly(¥)
<100	2039	57.0
100-399	1125	31.5
≥400	411	11.5
Father’s education
Primary school	838	23.4
Middle school	1215	34.0
University and above	1522	42.6
Mother’s education
Primary school	978	27.4
Middle school	1165	32.6
University and above	1432	40.0