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Table 4 Mixtures described by Day-Type, number of days and mean concentration

From: Associations between ambient air pollutant mixtures and pediatric asthma emergency department visits in three cities: a classification and regression tree approach

Labela Day-Typeb O3/NO2/PM2.5 All Atlanta Dallas St. Louis O3c NO2c PM2.5c
N N N N Mean(SD) Mean(SD) Mean(SD)
Referent 1/1/1 842 606 121 115 25.9 (6.3) 15.4 (3.8) 8.2 (1.7)
Mixture 1 1/1/2, 1/1/3, 2/1/2, 2/1/3 652 431 134 87 32.3 (9.4) 16.4 (3.4) 13.2 (1.6)
Mixture 2 1/1/4, 2/1/4 99 49 25 25 33.1 (10.2) 16.5 (3.5) 19.8 (3)
Mixture 3 1/2/2, 1/2/3 248 126 13 109 23 (7.2) 22.9 (1.2) 13.3 (1.5)
Mixture 4 1/3/1, 1/3/2, 1/3/3, 1/3/4 642 210 85 347 24.8 (7) 27.5 (1.4) 12 (3.9)
Mixture 5 1/4/1, 1/4/2, 1/4/3, 1/4/4, 2/4/1, 2/4/2, 2/4/3, 2/4/4 855 173 196 486 30 (8.9) 34.7 (4.1) 13.3 (5.2)
Mixture 6 2/2/2, 2/2/3 107 63 15 29 40.3 (2.8) 23 (1.1) 13.1 (1.6)
Mixture 7 2/3/1, 2/3/2, 2/3/3, 2/3/4 257 110 38 109 40.1 (2.8) 27.3 (1.4) 11.3 (3.5)
Mixture 8 3/1/1, 3/2/1 267 156 76 35 49.3 (2.8) 18 (4.2) 9.2 (1.4)
Mixture 9 3/1/2, 3/1/3 333 242 64 27 50 (3) 16.3 (3) 13.7 (1.6)
Mixture 10 3/1/4, 3/2/4 161 119 16 26 50.9 (2.8) 18.7 (3.9) 19.9 (2.8)
Mixture 11 3/2/2, 3/2/3 131 68 27 36 49.4 (2.8) 22.9 (1.2) 13.7 (1.6)
Mixture 12 3/3/1, 3/4/1 163 25 63 75 49.7 (2.7) 31 (4.3) 9.1 (1.4)
Mixture 13 3/3/2, 3/3/3, 3/3/4, 3/4/2, 3/4/3, 3/4/4 356 163 36 157 50 (2.9) 31.7 (5.4) 15.6 (4.2)
Mixture 14 4/1/2, 4/1/3, 205 149 42 14 61.4 (5.6) 17.3 (2.8) 14.3 (1.7)
Mixture 15 4/2/2, 4/2/3 128 77 36 15 63.1 (6.1) 23.1 (1.1) 14.3 (1.7)
Mixture 16 4/3/1, 4/3/2, 4/3/3, 4/3/4 392 207 72 113 67.2 (10.7) 27.4 (1.4) 19.1 (6.6)
Mixture 17 4/4/1, 4/4/2, 4/4/3, 4/4/4 450 156 58 236 68.5 (11.2) 35.7 (4.9) 19.7 (6.3)
  1. SD standard deviation
  2. aMixture labels are arbitrary and ordered according to level of O3, followed by NO2
  3. bDay-Types are represented by the level of O3, NO2 and PM2.5 respectively
  4. cMean concentrations and standard deviations are presented for the 3-day population weighted average of O3 (ppb), NO2 (ppb) and PM2.5 (μg/m3)