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Table 4 Percent excess risk associated with SO2 exposure at lag 0–2 (both for exposure as a continuous variable and for days with pollution levels above the air quality guideline value) and changes in respiratory health in diagnosis subcategories in primary care and hospital emergency departments in the capital area of Iceland

From: Severe volcanic SO2 exposure and respiratory morbidity in the Icelandic population – a register study

  Mean (SD) SO2 (per 10 μg/m3)a SO2 levels > 125 SO2 μg/m3
% 95% CI % 95% CI
Anti-asthma medication
 Short-acting β-agonist (R03A) 88 (47.2) 1.09% 0.49% 1.70% 13.7% 4.5% 23.7%
 Long-acting (R03B) 38.7 (21.4) 0.74% −0.03% 1.52% 8.7% −2.2% 20.7%
Primary care MD visits (PCMD)
 Respiratory infections (J0-J2) 108.6 (46.2) 1.12 0.54% 1.71% 15.8% 7.2% 25.1%
 Asthma and COPD (J44–45) 15.6 (9.6) 2.08% 1.13% 3.04% 28.4% 12.8% 46.2%
Hospital emergency department visits (HED)
 Respiratory infections (J0-J2) 9.3 (4.3) 1.09% −0.22% 2.41% 7.9% −60.9% 27.8%
 Asthma and COPD (J44–45) 4.3 (2.7) 0.95% −0.99% 2.93% 3.3% −19.8% 33.2%
  1. aAdjusted for season (spline), time trend (spline), day of week, odd holidays 1, temperature (spline), relative humidity, NO2, PM10 at the same lags as SO2, and the outcome at lag