Table 3.
Summary of GIS-derived and meteorological covariates included in the final model
| Category | Description | Unitsb | Time-varying? | Summary of covariate distribution | Edf of smooth termc | ||||
|---|---|---|---|---|---|---|---|---|---|
| 5% | 25% | 50% | 75% | 95% | |||||
| Distance to road | Distance to nearest A1 roada | ln(m) | No | 4.7 | 6.7 | 7.8 | 9.2 | 10.9 | 2.5 |
| Distance to nearest A2 roada | ln(m) | No | 3.9 | 5.9 | 7.2 | 8.2 | 9.3 | 1.0 | |
| Distance to nearest A3 roada | ln(m) | No | 3.5 | 5.7 | 6.7 | 7.6 | 8.7 | 1.0 | |
|
| |||||||||
| Urban land use | Percentage of urban land use within 1 km | % | No | 0.1 | 21.0 | 59.7 | 81.7 | 95.4 | 2.4 |
|
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| Population density | Block group population density | persons mile−2 | No | 26 | 174 | 1 441 | 4 640 | 15 650 | 4.5 |
| County population density | persons mile−2 | No | 24 | 140 | 375 | 1 428 | 11 038 | 4.9 | |
|
| |||||||||
| Point source emissions | PM10 emissions within 1 km | ln(tons year−1) | No | −6.9 | −6.9 | −6.9 | 0.7 | 5.1 | 1.0 |
| PM10 emissions within 10 km | ln(tons year−1) | No | −6.5 | 4.2 | 5.8 | 7.0 | 8.5 | 2.3 | |
|
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| Elevation | Elevation above sea-level | m | No | 3.4 | 48.2 | 176.4 | 233.3 | 359.0 | 1.4 |
|
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| Area-source emissions | PM10 emissions by county and year | ln(tons year−1) | Yes | 7.4 | 8.7 | 9.3 | 10.0 | 10.7 | 7.2 |
|
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| Precipitation | Total monthly precipitation | inches (cm) | Yes | 1.2 (3.0) | 2.2 (5.6) | 3.2 (8.1) | 4.5 (11.4) | 6.9 (17.5) | 7.6 |
|
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| Wind speed | Monthly-average surface wind speed | m s−1 | Yes | 2.6 | 3.3 | 3.8 | 4.3 | 4.8 | 6.4 |
a
Designated by Census Feature Class Codes, from ESRI StreetMap road data.
b
ln’ is natural log.
c
Edf is estimated degrees of freedom of smooth term in the final model.