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Table 3 Excess risks (ERs) and 95% confidence intervals of preterm birth per IQR increment in air pollutant concentrations in warm and cold periods in Ningbo, China

From: Association between ambient air pollutants and preterm birth in Ningbo, China: a time-series study

  All births Gestational women age between 18 and 35 Gestational women under 18 or above 35
Annual Cold period Warm period Annual Cold period Warm period Annual Cold period Warm period
PM2.5b 4.84 (1.77,8.00) c 4.92 (1.47,8.50) c 4.06 (− 2.55,11.12) 4.53 (1.09,8.09) c 4.65 (0.71,8.74) c 3.17 (− 4.23,11.15) 9.40 (0.74,18.80) c 12.24 (2.40,23.04) c − 1.93 (− 18.95,18.67)
PM10b 3.56 (0.07,7.17) c 5.11 (1.04,9.35) c 1.87 (−5.26,9.53) 4.88 (0.88,9.03) c 6.74 (2.12,11.58) c 2.64 (− 5.42,11.39) 13.22 (2.55,25.00) c 16.73 (4.50,30.40) c 0.65 (−19.38,25.66)
SO2b 3.65 (0.86,6.51) c 4.93 (1.64,8.33) c 1.44 (− 3.70,6.85) 6.56 (3.39,9.82) c 7.04 (3.29,10.92) c 5.53 (−0.32,11.71) 8.46 (0.21,17.40) c 10.95 (1.37,21.45) c 2.79 (− 12.58,20.87)
NO2b 6.49 (1.86,11.34) c 9.25(3.45,15.38) c 3.12(−5.08,12.02) 6.66(1.42,12.17) c 10.32(3.69,17.37) c 2.7(−6.26,12.51) 14.20 (1.18,28.90) c 7.40(−7.79,25.09) −2.94(− 23.32,22.87)
O3b − 0.90 (− 4.76,3.11) −6.35 (− 12.78,0.55) 3.23 (− 1.81,8.53) − 2.76 (− 7.1,1.79) − 3.86 (− 10.69,3.49) 1.55 (− 3.91,7.32) −4.11 (− 14.14,7.10) −8.96 (− 24.85,10.28) −1.23 (− 14.53,14.15)
COb 3.36 (0.50,6.30) c 5.16 (1.33,9.13) c 1.89 (−2.71,6.71) 0.37 (−2.84,3.70) 2.29 (− 1.16,5.87) 0.40 (− 4.60,5.66) 7.82 (0.85,15.28) c 10.44 (1.71,19.92) c 4.14 (−7.37,17.08)
  1. PM2.5: particulate matter less than 2.5 μm in aerodynamic diameter, PM10: particulate matter less than 10 μm in aerodynamic diameter, SO2: sulfur dioxide, NO2: nitrogen dioxide, O3: Ozone, CO: carbon monoxide
  2. aERs were calculated per IQR increment for each air pollutant
  3. bLag day (lag 3 for PM2.5, PM10, NO2, SO2, O3, lag4 for CO) were used
  4. cP<0.05
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