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. Author manuscript; available in PMC: 2012 Jul 1.
Published in final edited form as: Environ Res. 2011 Mar 30;111(5):685–692. doi: 10.1016/j.envres.2011.03.008

Table 2.

Means, inter-quartile ranges and Pearson’s correlation coefficients for different exposure measures for the entire pregnancy.

Pollutant n Mean±SDa IQRa, b Pearson r
Measured pollutantc LUR (unadjusted) LUR (adjusted) CALINE4 Traffic density
CO NO NO2 NOx O3 PM10 PM2.5 NO NO2 NOx NO NO2 NOx NOx PM2.5
Measured pollutantc CO 81186 0.7+0.4 0.5 1.00
NO 81186 30.9+15.7 18.3 0.85 1.00
NO2 81186 24.9+7.4 11.7 0.83 0.83 1.00
NOx 81186 55.8+22.2 28.2 0.88 0.98 0.92 1.00
O3 81186 35.6+7.5 11.5 −0.74 −0.80 −0.81 −0.84 1.00
PM10 81186 32.7+5.7 6.8 0.60 0.51 0.70 0.59 −0.49 1.00
PM2.5 68055 17.3+3.5 5.1 0.77 0.65 0.77 0.72 −0.61 0.86 1.00
LUR (unadjusted) NO 81186 25.2+10.9 8.2 0.03 0.03 0.01 0.02 0.02 0.06 0.05 1.00
NO2 81186 22.4+3.6 4.3 0.09 0.06 0.06 0.06 0.05 0.05 0.06 0.39 1.00
NOx 81186 48.6+10.8 12.1 0.05 0.04 0.01 0.03 0.06 0.05 0.05 0.72 0.87 1.00
LUR (adjusted) NO 81186 30.9+18.1 11.6 0.24 0.35 0.20 0.32 −0.24 0.23 0.25 0.76 0.26 0.53 1.00
NO2 81186 28.0+7.0 5.1 0.43 0.42 0.57 0.49 −0.39 0.52 0.52 0.25 0.63 0.55 0.48 1.00
NOx 81186 59.9+20.3 15.6 0.36 0.48 0.38 0.46 −0.35 0.37 0.39 0.47 0.53 0.64 0.80 0.84 1.00
CALINE4 NOx 79629 7.2+5.2 5.6 0.43 0.41 0.50 0.45 −0.37 0.41 0.43 0.24 0.56 0.51 0.25 0.63 0.49 1.00
PM2.5 79629 1.8+1.3 1.4 0.22 0.21 0.25 0.23 −0.15 0.19 0.21 0.29 0.63 0.58 0.16 0.44 0.34 0.89 1.00
Traffic density 81186 73.8+116.3 76.6 0.07 0.06 0.09 0.07 −0.05 0.09 0.09 0.28 0.37 0.43 0.19 0.27 0.27 0.58 0.61 1.00
a

The units of exposure are parts per million (ppm) for CO, parts per billion (ppb) for NO, NO2, NOx, and O3, and μg m−3 for PM10 and PM2.5. The unit for traffic density is vehicle number per day*meter/meter2.

b

Inter-quartile range

c

Exposure was assigned based on residential distance to the nearest air quality monitoring station with valid measurement data. All exposures were averaged over 24 hours except O3, which was averaged over 8 hours from 10 AM to 6 PM. PM2.5 data were first collected in 2000 while data for the other pollutants were available starting in 1997.