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Time Series Study of Air Pollution Health Effects in COPSAC Children

Appendix A

Correlation between pollutants measured at the same station, and correlation between pollutants measured at HCØ and weather variables (Pearson correlation coefficients presented in Tables A.1-A.4)

In all three measuring stations we find consistent results. According to Tables A.1 – A.3, there is significant positive correlation between CO and NOx, CO and NO2, CO and PM10, Co and TON (nonsignificant at HCØ), NOx and NO2, NOx and PM10 , NOx and TON, NO2 and PM10 , NO2 and TON, and PM10 and TON. There is negative significant association between O3 and all other pollutants measured at all three stations, except with PM10 measured at HCØ where it is not significant. These tables illustrate high correlation between pollutants, which is informative in interpreting and understanding results, and useful for planning possible future analyses with multiple pollutant models.

Table A.1: Correlation between pollutants measured at HCØ (City Background Pollution Levels) from 02.08.1998 – 29.06.2003

  CO NOx NO2 O3 PM10 TON
CO 1.00 0.827* 0.761* -0.727* 0.511* 0.525
NOx   1.00 0.919* -0.619* 0.391* 0.616*
NO2     1.00 -0.586* 0.447* 0.650*
O3       1.00 -0.40 na
PM10         1.00 0.383*
TON           1.00

* p < 0.01 - significance level for the Pearson correlation coefficients

Table A.2: Correlation between pollutants measured at Jagtvej (Street Pollution Levels) from 02.08.1998 – 29.06.2003

  CO NOx NO2 O3 PM10 TON
CO 1.00 0.937* 0.751* -0.660* 0.492* 0.917*
NOx   1.00 0.832* -0.648* 0.488* 0.953*
NO2     1.00 -0.422* 0.536* 0.847*
O3       1.00 -0.237* -0.720*
PM10         1.00 0.577*
TON           1.00

* p < 0.01 - significance level for the Pearson correlation coefficients

Table A.3: Correlation between pollutants measured at HCAB (Street Pollution Levels) from 02.08.1998 – 29.06.2003

  CO NOx NO2 O3 PM2,5 TON
CO 1.00 0.913* 0.695* -0.670* 0.603* 0.825*
NOx   1.00 0.798* -0.645* 0.436* 0.755*
NO2     1.00 -0.365* 0.529* 0.556*
O3       1.00 -0.191* -0.505*
PM2,5         1.00 0.763*
TON           1.00

* p < 0.01 - significance level for the Pearson correlation coefficients

In Table A.4 below it can be seen that there is high correlation between pollutants and weather variables. There is negative significant correlation between Wind Speed and all pollutants expect O3. Temparature is significantly negatively correlated with CO, NOx, and NO2, and significantly positevly correlated with O3. Similar to temperature, global radiation is significantly negatively correlated with CO, NOx, and NO2, and significantly positevly correlated with O3. Relative humidty is significantly positively correlated with CO and NO2, while significantly negatively correlated with NO2 and O3. There is very week association observed between temperature and PM10,temperature and TON, global radiation and PM10, global radiation and TON, relative humidity and PM10, and relative humidity and TON. These results are useful in building models, for example, when consideting colinearity problems, and in interpreting and understanding results.

Table A.4: Correlation between pollutants and weather variables (all measured at HCØ) during study period (02.08.1998 – 29.06.2003)

  Wind Speed Temperature Global Radiation Relative Humidity
CO -0.356* -0.452* -0.390* 0.326*
NOx -0.460* -0.241* -0.229* -0.213*
NO2 -0.445* -0.224* -0.201* 0.177*
O3 0.054 0.583* 0.660* -0.645*
PM10 -0.220* 0.036 -0.004 0.079
TON -0.457* -0.075 0.072 -0.056

* p < 0.01 - significance level for the Pearson correlation coefficients

 

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Version 1.0 Maj 2005, © Danish Environmental Protection Agency