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Table 3 Differences in nephrotic syndrome incidences and associated HRs in participants exposed to various daily average concentrations of air pollutants stratified by 3 period of time in 2000–2012

From: Association between gaseous air pollutants and idiopathic nephrotic syndrome in children: a 12-year population-based cohort study

  Event PYa IRb cHRc 95%CI aHRd 95% CIe
Year 2000–2004
SO2
  Quartile 1, < 3.38 ppb 7 155,855 0.45 Reference group Reference group
  Quartile 2, 3.38–4.32 ppb 12 211,515 0.47 1.26 (0.50, 3.21) 1.37 (0.54, 3.51)
  Quartile 3, 4.32–6.03 ppb 24 338,017 0.71 1.58 (0.68, 3.67) 1.81 (0.77, 4.25)
  Quartile 4, > 6.03 ppb 38 304,390 1.25 2.78 (1.24, 6.22)* 3.11 (1.37, 7.04)**
THC
  Quartile 1, < 2.29 ppm 3 267,526 0.11 Reference group Reference group
  Quartile 2, 2.29–2.38 ppm 3 200,539 0.15 1.33 (0.27, 6.60) 1.37 (0.28, 6.76)
  Quartile 3, 2.38–2.60 ppm 51 336,769 1.51 13.5 (4.21, 43.2)*** 16.3 (5.05, 52.5)***
  Quartile 4, > 2.60 ppm 24 204,943 1.17 10.4 (3.14, 34.6)*** 14.6 (4.32, 49.4)***
CH4
  Quartile 1, < 2.01 ppm 0 245,282 0.00   
  Quartile 2, 2.01–2.06 ppm 5 264,136 0.19 Reference group Reference group
  Quartile 3, 2.06–2.11 ppm 19 261,444 0.73 3.84 (1.43, 10.3)** 4.07 (1.52, 10.9)**
  Quartile 4, > 2.11 ppm 57 238,914 2.39 12.6 (5.04, 31.3)*** 15.0 (5.96, 37.7)***
Year 2005–2008
SO2
  Quartile 1, < 3.38 ppb 8 144,717 0.55 Reference group Reference group
  Quartile 2, 3.38–4.32 ppb 8 201,468 0.40 0.72 (0.27, 1.91) 0.71 (0.27, 1.90)
  Quartile 3, 4.32–6.03 ppb 26 307,104 0.85 1.53 (0.69, 3.39) 1.50 (0.67, 3.37)
  Quartile 4, > 6.03 ppb 48 281,274 1.71 3.09 (1.46, 6.53)** 3.00 (1.41, 6.40)**
THC
  Quartile 1, < 2.29 ppm 6 262,547 0.23 Reference group Reference group
  Quartile 2, 2.29–2.38 ppm 12 196,383 0.61 2.67 (1.00, 7.12)* 2.70 (1.01, 7.18)*
  Quartile 3, 2.38–2.60 ppm 43 301,098 1.43 6.27 (2.67, 14.7)*** 6.12 (2.59, 14.5)***
  Quartile 4, > 2.60 ppm 29 174,535 1.66 7.31 (3.03, 17.6)*** 7.02 (2.86, 17.2)***
CH4
  Quartile 1, < 2.01 ppm 5 241,793 0.21 Reference group Reference group
  Quartile 2, 2.01–2.06 ppm 8 254,354 0.31 1.52 (0.50, 4.65) 1.52 (0.50, 4.65)
  Quartile 3, 2.06–2.11 ppm 22 248,155 0.89 4.29 (1.62, 11.3)** 4.19 (1.58, 11.1)**
  Quartile 4, > 2.11 ppm 55 190,262 2.89 14.1 (5.66, 35.3)*** 13.4 (5.35, 33.7)***
Year 2009–2012
SO2
  Quartile 1, < 3.38 ppb 18 131,135 1.37 Reference group Reference group
  Quartile 2, 3.38–4.32 ppb 19 176,467 1.08 0.78 (0.41, 1.49) 0.79 (0.41, 1.51)
  Quartile 3, 4.32–6.03 ppb 33 269,725 1.22 0.89 (0.50, 1.58) 0.90 (0.50, 1.62)
  Quartile 4, > 6.03 ppb 23 240,350 0.96 0.69 (0.37, 1.29) 0.99 (0.88, 1.12)
THC
  Quartile 1, < 2.29 ppm 22 250,851 0.88 Reference group Reference group
  Quartile 2, 2.29–2.38 ppm 33 186,270 1.77 2.02 (1.18, 3.47)* 2.02 (1.18, 3.47)*
  Quartile 3, 2.38–2.60 ppm 27 251,963 1.07 1.22 (0.69, 2.14) 1.22 (0.69, 2.15)
  Quartile 4, > 2.60 ppm 11 128,593 0.86 0.97 (0.47, 2.00) 0.97 (0.46, 2.02)
CH4
  Quartile 1, < 2.01 ppm 18 221,684 0.81 Reference group Reference group
  Quartile 2, 2.01–2.06 ppm 17 247,435 0.69 0.85 (0.44, 1.65) 0.85 (0.44, 1.66)
  Quartile 3, 2.06–2.11 ppm 36 216,749 1.66 2.04 (1.16, 3.59)* 2.07 (1.17, 3.65)*
  Quartile 4, > 2.11 ppm 22 131,809 1.67 2.05 (1.10, 3.82)* 2.05 (1.10, 3.83)*
  1. aPY person-years, bIR incidence rate, (per 10,000 person-years), ccHR crude hazard ratio, daHR adjusted hazard ratio, adjustment for age, sex, monthly income, and urbanization level, eCI confidence interval. *p < 0.05; **p < 0.01; ***p < 0.001