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Table 2 Characteristics and Spearman correlation coefficients for hourly air pollutants and meteorological variables

From: Hourly differences in air pollution and risk of respiratory disease in the elderly: a time-stratified case-crossover study

 

Mean (SD)

IQR

SPM

NO2

SO2

Ozone

CO

Temperature

Relative humidity

All day

Daytime (8 am to 7 pm)

Nighttime (8 pm to 7 am)

SPM (μg/m3)

26.8 (18.3)

27.5 (18.4)

26.1 (18.1)

20.6

1

0.41

0.50

0.06

0.35

0.23

0.00

NO2 (ppb)

17.1 (8.1)

15.9 (7.9)

18.3 (8.2)

11.1

 

1

0.40

−0.40

0.63

−0.26

0.20

SO2 (ppb)

3.0 (2.5)

3.7 (3.0)

2.3 (1.7)

2.3

  

1

0.26

0.19

0.22

−0.31

Ozone (ppb)

25.9 (17.9)

33.8 (18.5)

18.1 (13.1)

25.8

   

1

−0.31

0.36

−0.65

CO (ppm)

0.6 (0.3)

0.6 (0.3)

0.6 (0.3)

0.3

    

1

−0.17

0.17

  1. CO, Carbon monoxide; IQR, Interquartile range; NO 2 , Nitrogen dioxide; SD, Standard deviation; SO 2 , Sulfate dioxide; SPM, Suspended particulate matter.