Table 1. Subject characteristics and their PM2.5 exposures measured as 5-year averages from 2013–1017 for both exposure concentration and average daily dose (ADD).
| Variables | Mean ± SD or N (%) | PM2.5 (µg/m3) | ADD (µg/kg-d) |
|---|---|---|---|
| Height, cm | 138±9 | / | / |
| Weight, kg | 34±10 | / | / |
| BMI, kg/m2 | 18±4 | / | / |
| Area of residence | / | / | |
| Suburban | 492 (71.9) | 47.6±0.2** | 50.0±5.3* |
| Urban | 192 (28.1) | 49.1±4.1 | 51.5±6.7 |
| Gender | |||
| Male | 371 (54.24) | 48.1±2.7 | 51.7±5.7** |
| Female | 313 (45.76) | 48.0±1.9 | 49.1±5.6 |
| Age | |||
| <8 | 40 (5.85) | 48.1±2.9** | 51.8±5.3** |
| 8–10 | 498 (72.81) | 48.0±2.0 | 51.0±5.1 |
| >10 | 146 (21.35) | 48.5±3.1 | 48.5±7.5 |
| Parental smoking | |||
| No | 249 (36.40) | 47.6±0.3** | 50.2±4.7 |
| Yes | 391 (57.16) | 48.4±3.0 | 50.7±6.3 |
| Missinga | 44 (6.43) | / | / |
| Kitchen style | |||
| Closed | 440 (64.33) | 47.9±2.0** | 50.4±5.8 |
| Open | 244 (35.67) | 48.4±2.9 | 50.8±5.7 |
| Cooking fuel | |||
| Solid | 31 (4.53) | 49.1±4.0* | 52.4±7.0 |
| Clean | 627 (91.67) | 48.0±2.3 | 50.4±5.6 |
| Missing | 26 (3.80) | / | / |
| Kitchen ventilation | |||
| No | 9 (1.32) | 49.8±5.2** | 52.2±6.7 |
| Yes | 675 (98.68) | 48.1±2.3 | 50.5±5.8 |
| Heating in winter | |||
| Yes | 648 (94.74) | 48.1±2.4* | 50.5±5.8 |
| No | 36 (5.26) | 48.3±2.7 | 50.5±6.2 |
| Heating fuel | |||
| None/central/gas/electricity | 536 (78.36) | 47.9±1.8** | 50.4±5.6 |
| Coal | 117 (17.11) | 48.9±4.1 | 51.0±6.4 |
| Missing | 31 (4.53) | / | / |
| Air fresher use | |||
| Yes | 150 (21.93) | 48.3±3.3 | 51.4±6.0* |
| No | 534 (78.07) | 48.0±2.0 | 50.3±5.7 |
| Asthma in past year | |||
| No | 676 (98.83) | 48.1±2.4 | 50.5±5.8 |
| Yes | 8 (1.17) | 48.1±0.3 | 52.7±2.1 |
| Paternal education | |||
| Below senior high school | 326 (47.66) | 48.2±2.9 | 51.1±5.9* |
| Senior high school and above | 358 (52.34) | 48.0±1.8 | 49.9±5.6 |
| Maternal education | |||
| Below senior high school | 347 (50.73) | 48.2±2.9* | 51.1±6.1* |
| Senior high school and above | 337 (49.27) | 47.9±1.6 | 49.8±5.3 |
| Paternal asthma | |||
| No | 677 (98.98) | 48.1±2.4 | 50.5±5.8 |
| Yes | 7 (1.02) | 47.9±0.3 | 49.9±4.6 |
| Maternal asthma | |||
| No | 680 (99.42) | 48.1±2.4* | 50.5±5.8 |
| Yes | 4 (0.58) | 48.2±0.0 | 54.5±3.3 |
| Fruit consumption | |||
| Below referenceb | 299 (43.71) | 48.1±2.3* | 51.0±5.6* |
| Above/with reference | 370 (54.09) | 48.1±2.4 | 50.1±5.9 |
| Missing | 15 (2.19) | / | / |
| Dairy consumption | |||
| Below referencec | 172 (25.15) | 48.5±3.3** | 51.2±6.0 |
| Above/with reference | 497 (72.66) | 47.9±2.0 | 50.3±5.7 |
| Missing | 15 (2.19) | / | / |
a, the missing value of a variable; b, fruit intake reference, once a day; c, dairy intake reference, 5 to 6 times a week; **, P<0.001; *, P<0.05.