Figure 2From: Hourly differences in air pollution and risk of respiratory disease in the elderly: a time-stratified case-crossover study Odds ratios of pneumonia and influenza for an interquartile range increase in (a) suspended particulate matter (20.6 μg/m 3 ), (b) sulfur dioxide (2.3 ppb), and (c) ozone (25.8 ppb) in the hours prior to disease onset. Vertical bars indicate 95% confidence intervals.Back to article page