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Table 2 Frequency distribution of the daily pollution levels for gaseous and particulate phase pollutants

From: Outdoor air pollution and emergency department visits for asthma among children and adults: A case-crossover study in northern Alberta, Canada

  Summer (April to September) Winter (October to March)
  Days* 25th P 75th P Med Days* 25th P 75th P Med
SO2 (ppb) 1830 1.0 3.0 2.0 1822 2.0 4.0 3.0
NO2 (ppb) 1830 14.0 22.0 17.5 1822 22.5 35.5 28.5
CO (ppm) 1830 0.5 0.7 0.6 1822 0.7 1.3 0.9
O3- daily max (ppb) 1830 29.5 46.0 38.0 1822 16.5 31.5 24.3
PM2.5: g/m3 715 4.5 11.0 7.0 729 5.0 11.0 7.3
PM10: g/m3 732 15.0 32.5 22.0 819 13.0 29.0 19.0
Temperature (°C) 1830 9.8 17.2 13.9 1822 -11.1 1.6 -3.8
Relative humidity (%) 1830 53.0 72.8 63.0 1822 60.9 78.0 68.8
Aeroallergens†         
Grasses (spores/m3) 1098 0.0 5.7 1.0 1093 0.0 0.0 0.0
Trees (spores/m3) 1098 0.0 42.2 3.4 1093 0.0 0.0 0.0
Weeds (grains/m3) 1098 0.0 5.0 0.0 1093 0.0 0.0 0.0
Deuteromycetes (spores/m3) 1098 350.4 2303.7 1096.9 1093 0.0 0.0 0.0
Basidiomycetes(spores/m3) 1098 19.1 442.8 124.8 1093 0.0 0.0 0.0
Asomycetes (spores/m3) 1098 59.1 519.4 194.2 1093 0.0 0.0 0.0
  1. * Number of days with non-missing values;
  2. ≸Aeroallergen data available from 1996 to 2002
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