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. Author manuscript; available in PMC: 2020 Apr 1.
Published in final edited form as: Environ Res. 2018 Oct 28;171:36–43. doi: 10.1016/j.envres.2018.10.027

Table 2.

Characteristics and the Spearman correlation coefficients between the 1-day moving averages of measured ambient air pollutants.

Pollutant Number
of observations		 Mean (SD) Interquartile
Range		 Spearman Correlation Coefficients
BC SO42− NOx O3
PM2.5, μg/m3 5206 10.2 (6.1) 6.4 0.73 0.82 0.41 0.00
BC, μg/m3 5205 0.8 (0.5) 0.5 0.53 0.57 −0.25
SO42−, μg/m3 4461 3.2 (2.5) 2.4 0.28 0.11
NOx, ppb 4912 39.1 (21.0) 19.7 −0.55
O3, ppb 5207 23.2 (11.2) 15.4

Abbreviation: PM2.5, fine particulate matter; BC, black carbon; SO42−, sulfate; NOx, nitrogen oxides; O3, ozone.