Table 3. Characteristics of participants, by citya .
| Shenyang | Dalian | Anshan | Fushun | Benxi | Liaoyang | Yingkou | |
| n | 2244 | 984 | 1046 | 780 | 606 | 633 | 437 |
| Age, mean (SD), years | 4.7 (0.9) | 4.8 (0.7) | 4.8 (1.0) | 4.7 (0.8) | 4.8 (0.7) | 4.7 (0.9) | 5.7 (0.6) |
| Male | 51.1 | 50.5 | 46.4 | 51.7 | 52.0 | 50.4 | 54.0 |
| Breast feeding | 71.4 | 82.8 | 74.6 | 80.6 | 89.8 | 82.9 | 82.2 |
| Parental education <high school graduate | 9.9 | 8.2 | 31.2 | 29.1 | 11.2 | 13.3 | 12.1 |
| Family history of allergy | 13.2 | 19.1 | 12.2 | 15.3 | 17.3 | 10.3 | 9.8 |
| Family history of asthma | 7.3 | 10.4 | 4.4 | 6.9 | 9.1 | 5.1 | 4.8 |
| House near main road | 32.8 | 46.3 | 39.7 | 51.2 | 49.7 | 42.5 | 38.7 |
| House near factory or chimney | 12.2 | 14.1 | 16.0 | 21.4 | 33.3 | 17.7 | 13.3 |
| Home coal use | 2.0 | 2.1 | 3.1 | 11.8 | 5.5 | 3.3 | 2.8 |
| Ventilation device | 68.5 | 76.5 | 51.4 | 37.7 | 54.5 | 48.7 | 52.6 |
| House pets | 8.6 | 11.2 | 18.0 | 12.7 | 9.6 | 13.6 | 11.0 |
| Home decoration | 42.9 | 37.6 | 28.9 | 19.1 | 30.7 | 34.9 | 33.6 |
| Early ETS exposure | 16.4 | 19.0 | 24.9 | 34.4 | 21.5 | 21.2 | 25.2 |
| Current ETS exposure | 44.2 | 49.9 | 49.1 | 65.8 | 51.3 | 45.3 | 50.1 |
| Persistent cough | 11.9 | 17.9 | 7.7 | 18.1 | 17.7 | 11.4 | 8.7 |
| Persistent phlegm | 4.4 | 7.1 | 5.2 | 8.6 | 5.6 | 5.1 | 3.2 |
| Asthma symptoms | 8.0 | 9.6 | 6.5 | 8.5 | 6.4 | 5.1 | 6.2 |
| Current asthma | 3.8 | 4.7 | 1.5 | 3.9 | 3.1 | 3.0 | 3.4 |
| Wheezing | 10.1 | 12.2 | 5.1 | 13.3 | 14.9 | 10.7 | 12.4 |
| Allergy rhinitis | 2.9 | 6.5 | 2.3 | 1.5 | 3.1 | 1.0 | 0.9 |
ETS, environmental tobacco smoke.
aValues are percentages unless otherwise specified.