Table 4.
Results of linear regression modeling for ratios of home outdoor to central site measurements of PM2.5, OC, and EC
| Dependent variable | N | Predictor variable | Estimate | SE | Partial R 2 | Adj. model R 2 |
|---|---|---|---|---|---|---|
| Model | ||||||
| PM2.5 ratio | ||||||
| Riverside | 62 | Population density (per km2) | 1.7E-04** | 2.7E-05 | 0.36 | 0.43 |
| Relative humidity at central site (%) | 4.3E-03** | 1.1E-03 | 0.07 | |||
| Average wind direction from N to E | 0.12 | 0.07 | 0.03 | |||
| Whittier | 69 | Frequency of wind direction from N to E | 0.02** | 0.01 | 0.24 | 0.31 |
| Weekly time term (cos) | −0.09** | 0.03 | 0.08 | |||
| Average wind direction from W to N | 0.20 | 0.11 | 0.02 | |||
| Pooled | 131 | Minimal distance to highway (m) | −5.3E-05** | 1.1E-05 | 0.24 | 0.38 |
| Frequency of wind direction from N to E | 0.02** | 4.8E-03 | 0.06 | |||
| Average temperature at central site (°F) | −0.01* | 2.1E-03 | 0.05 | |||
| Weekly time term (cos) | −0.08** | 0.03 | 0.05 | |||
| city | 0.04 | 0.07 | 2.0E-03 | |||
| Average wind direction from W to N | 0.10 | 0.05 | 5.4E-05 | |||
| OC ratio | ||||||
| Riverside | 55 | Heavy-duty vehicle traffic count (distance weighted) | 0.01** | 1.2E-03 | 0.47 | 0.70 |
| Relative humidity at central site (%) | 3.3E-03** | 9.0E-04 | 0.09 | |||
| Average wind speed (miles/h) | 0.09** | 0.02 | 0.09 | |||
| Weekly time term (sin) | 0.05* | 0.02 | 0.03 | |||
| Frequency of wind direction from N to E | 0.02* | 0.01 | 0.02 | |||
| Average wind direction from N to E | −0.26** | 0.07 | 0.02 | |||
| Whittier | 75 | Average temperature at central site (°F) | −0.02** | 4.1E-03 | 0.45 | 0.58 |
| Average wind direction from W to N | 0.35** | 0.11 | 0.07 | |||
| Weekly time term (cos) | −0.12** | 0.03 | 0.06 | |||
| Average wind speed (miles/h) | −0.10* | 0.04 | 0.02 | |||
| Heavy-duty vehicle traffic count (distance weighted) | 3.3E-03 | 1.7E-03 | 0.01 | |||
| Pooled | 75 | Minimal distance to collector road (m) | −4.2E-04** | 6.4E-05 | 0.24 | 0.63 |
| city | −0.03 | 0.05 | 0.17 | |||
| Frequency of wind direction from N to E | 0.04** | 0.01 | 0.08 | |||
| Average temperature at central site (°F) | −0.01* | 3.4E-03 | 0.06 | |||
| Relative humidity at central site (%) | 4.9E-03* | 1.9E-03 | 0.04 | |||
| Weekly time term (cos) | −0.08** | 0.02 | 0.03 | |||
| Daily time term (sin) | −0.05* | 0.02 | 0.01 | |||
| Average wind direction from N to E | −0.34** | 0.08 | 0.01 | |||
| EC ratio | ||||||
| Riverside | 55 | Relative humidity at central site (%) | 0.01** | 1.5E-03 | 0.34 | 0.66 |
| Minimal distance to highway (m) | −5.6E-05** | 9.5E-06 | 0.24 | |||
| Weekly time term (sin) | 0.07* | 0.03 | 0.04 | |||
| Average temperature at central site (°F) | 0.01 | 0.03 | 0.03 | |||
| Average wind speed (miles/h) | 0.07* | 0.03 | 0.03 | |||
| Average wind direction from S to W | 0.14* | 0.03 | 0.02 | |||
| Whittier | 75 | Ratio of EC CALINE4 home/central site estimates | 0.24** | 0.07 | 0.14 | 0.31 |
| Average temperature at central site (°F) | −0.03** | 0.01 | 0.14 | |||
| Average wind direction from N to E | −0.61* | 0.27 | 0.04 | |||
| Weekly time term (cos) | −0.12 | 0.07 | 0.03 | |||
| Pooled | 130 | Ratio of EC CALINE4 home/central site estimates | 0.22** | 0.08 | 0.41 | 0.53 |
| Population density (per km2) | −4.1E-06 | 4.3E-05 | 0.04 | |||
| Frequency of wind direction from N to E | 0.03* | 0.01 | 0.04 | |||
| Weekly time term (sin) | 0.11* | 0.05 | 0.02 | |||
| Daily time term (sin) | −0.08 | 0.04 | 0.02 | |||
| Frequency of wind direction from S to W | −0.02 | 0.01 | 0.01 | |||
| Average wind speed (miles/h) | 0.12* | 0.05 | 0.01 | |||
| Average wind direction from N to E | −0.52** | 0.16 | 0.01 | |||
| City | 0.32* | 0.15 | 4.1E-03 | |||
SE standard error
*p < 0.05; **p < 0.01