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Table 2 Summary statistics for air pollutant and meteorological variables

From: Low level air pollution and exacerbation of existing copd: a case crossover analysis

Pollutant or meteorological variable (units)a Minimum Maximum Mean ± St. dev Mean as % of NAAQSb
PM2.5 (ug/m3) 0.45 37.0 8.56 ± 5.4 71 %
NO2 (ppb) 2.79 40.0 11.0 ± 5.0 21 %
SO2 (ppb) 0.28 7.51 1.99 ± 0.91 7 %
Relative Humidity (%) 22.4 93.9 68.7 ± 13.9 --
Temperature (°F) 0.96 83.8 49.8 ± 17.1 --
Temperature (°C) −17.2 28.8 9.89 ± −8.3  
  1. aAir pollutants: based on daily averages measured in Worcester, Ware and Springfield
  2. Temperature and humidity: based on daily averages from Worcester Regional Airport
  3. bRelevant USEPA National Ambient Air Quality Standards (NAAQS)
  4. PM2.5 = 12 ug/m3 annual mean, averaged over 3 years
  5. NO2 = 53 ppb annual mean
  6. SO2 = 30 ppb annual mean (based on USEPA 1971 value, which was revoked in 2010 and replaced with a 1-h maximum)