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Table 2 Descriptive statistics for the daily number of air pollution concentrations

From: The association between air pollution and preterm birth and low birth weight in Guangdong, China

Pollutant (unit) \( \overline{x} \)±s P (25) Median P (75) Range Concentration limits
PM2.5 (μg/m3) 36.45 ± 18.54 22.00 33.00 47.00 11.00~126.00 75
PM10 (μg/m3) 55.45 ± 24.56 36.00 50.00 69.00 16.00~171.00 150
SO2 (μg/m3) 14.90 ± 5.35 11.00 14.00 18.00 6.00~42.00 150
NO2 (μg/m3) 26.37 ± 10.09 19.00 24.00 31.00 10.00~72.00 80
CO (mg/m3) 1.02 ± 0.21 0.87 0.97 1.16 0.66~1.85 4
O3 (μg/m3) 56.40 ± 19.11 42.00 52.00 68.00 17.00~123.00 160
  1. Note: Concentration limits of PM2.5, PM10, SO2, NO2 and CO: the maximum allowable value of the average concentration within any 24 h. Concentration limit of O3: the maximum allowable value of the average concentration within any 8 h