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. Author manuscript; available in PMC: 2021 Jul 29.
Published in final edited form as: Atmos Environ (1994). 2020 Jan 17;223:117267. doi: 10.1016/j.atmosenv.2020.117267

Table 2.

Statistic description of measured air pollutants and potential predictor variablesa

Variable Mean SD Minimum P25 Median P75 Maximum
PM2.5 (μg/m3) (n = 28) 52.9 6.1 42.6 49.0 53.0 56.2 68.8
BC (μg/m3) (n = 28) 8.3 1.2 6.4 7.3 8.6 9.3 9.9
NO2 (μg/m3) (n = 43) 25.9 5.6 15.5 22.4 24.9 28.7 40.3
Population count
500 m 4241 – 284 836 1442 5528 21018
3000 m 96527 – 10041 26923 47105 104400 416947
Length of first-class road (m)
500 m 1048 1982 0 0 0 1596 8047
3000 m 35459 30254 0 13449 26391 47657 127752
Length of third-class road (m)
500 m 5266 3934 0 1786 5390 7712 14498
3000 m 102592 87390 4135 28552 77710 161996 289990
Distance to the nearest first-class road (m) 1357 1567 12 308 895 1667 7447
Distance to the nearest third-class road (m) 150 197 0.5 55 73 172 1000
Farmland area (m2)
500 m 263177 244757 0 6168 242740 423513 785191
3000 m 15658107 7171735 548198 11562163 19093172 20817572 25068093
Emission of NOx from traffic (t)
5000 m 57 75 0 4 16 113 249
10000 m 133 118 3 35 98 167 402
a

The descriptive statistics of potential predictor variables were based on 43 monitoring sites. Abbreviations: PM2.5, particulate matter with aerodynamic diameter≤2.5 μm; NO2, nitrogen dioxide; BC, black carbon; SD, standard deviation. P25: the 25th percentile; P75: the 75th percentile.