Table 3. Summary of indoor formaldehyde levels and other environmental conditions.
| Classification | Subgroups | Number (person-days) | Formaldehyde* (ppb) | P value |
|---|---|---|---|---|
| All | 4,789 | 13.6 ± 16.4 | ||
| Season | Spring | 382 | 18.1 ± 20.6 | - |
| Summer | 1,327 | 16.5 ± 21.0 | 0.096 | |
| Fall | 1,736 | 12.5 ± 13.5 | < 0.0001 | |
| Winter | 1,344 | 10.8 ± 12.1 | < 0.0001 | |
| Gender | Boys | 3,581 | 15.0 ± 15.8 | < 0.0001 |
| Girls | 1,208 | 9.5 ± 17.5 | ||
| Age (yr) | < 6 | 3,118 | 14.4 ± 18.2 | < 0.0001 |
| ≥ 6 | 1,671 | 12.0 ± 12.5 | ||
| BMI (kg/m2) | ≤ 16.8 | 2,411 | 15.5 ± 18.6 | < 0.0001 |
| > 16.8 | 2,378 | 11.7 ± 13.7 | ||
| Presence of parental allergic diseases | (−) | 1,865 | 12.8 ± 14.4 | < 0.0001 |
| (+) | 2,631 | 15.1 ± 18.2 | ||
| Passive smoking | (−) | 2,273 | 13.1 ± 18.2 | < 0.0001 |
| (+) | 1,699 | 15.5 ± 15.4 | ||
| Indoor mold/dampness | (−) | 3,872 | 13.8 ± 17.1 | < 0.0001 |
| (+) | 617 | 16.4 ± 14.6 | ||
| Indoor temperature (°C) | ≤ 25.5 | 2,429 | 12.3 ± 16.5 | < 0.0001 |
| > 25.5 | 2,398 | 14.9 ± 16.3 | ||
| Indoor RH (%) | ≤ 40 | 1,086 | 8.1 ± 11.2 | - |
| 41–60 | 2,761 | 13.7 ± 14.8 | < 0.0001 | |
| > 60 | 942 | 19.6 ± 22.8 | < 0.0001 | |
Test for mean differences between subgroups except for season which was result from analysis of variance test.
BMI, body mass index; RH, relative humidity.
*The average concentration of formaldehyde presented as mean ± standard deviation.