Table 4. Linear Mixed Effect Modeling of ln-Transformed Personal PM2.5 Exposure.
| estimate (β) | 95% CI | GMRa | |
|---|---|---|---|
| fuel type | |||
| smokeless coal | ref. | 1.00 | |
| smoky coal | 0.27 | 0.02,0.52 | 1.31 |
| “mixed” coal | 0.35 | 0.06,0.64 | 1.42 |
| wood | 1.03 | 0.66,1.40 | 2.80 |
| plant materials | 0.43 | 0.02,0.84 | 1.54 |
| “mixed” fuel | 0.37 | 0.11,0.63 | 1.45 |
| stove design | |||
| vented stove | ref. | 1.00 | |
| unvented stove | 0.48 | 0.22,0.74 | 1.62 |
| portable stove | 0.26 | 0.06,0.47 | 1.30 |
| firepit | 0.38 | 0.10,0.66 | 1.47 |
| mixed ventilation stove | 0.2 | 0.03,0.36 | 1.22 |
| unknown ventilation stove | –0.34 | –0.77,0.09 | 0.71 |
| number of windows in main cooking room | |||
| none | ref. | 1.00 | |
| one | 0.22 | 0.01,0.44 | 1.25 |
| two | –0.01 | –0.26,0.23 | 0.99 |
| season | |||
| autumn | ref. | 1.00 | |
| winter | 0.19 | 0.02,0.36 | 1.21 |
| spring | –0.24 | –0.41,-0.07 | 0.79 |
| summer | –0.34 | –0.68,0.00 | 0.71 |
| number of hours burning fuel standardized by number of used stovesb | 0.01 | 0.003,0.03 | 1.01 |
| variation explained, % | |||
| between individual subjects | 35 | ||
| between villages | 79 | ||
| reference valuec, ln-μg/m3 | 4.35 |
a
Geometric mean ratio = GM(estimate)/GM(reference) = Exp(β).
b
Median period 4.3 h; IQR 2.2 to 9.6 h per stove.
c
Reference value represents base value of log transformed PM2.5 in model for reference group (smokeless coal burnt in a vented stove, during autumn in a room with no windows).