Fig. 2

The smoothed exposure-response curves between diurnal temperature range (DTR) and emergency room (ER) visits for upper respiratory tract infections (URI) in different subgroups in Seoul, Korea, 2009 to 2013. The line represents a spline curve and the shaded area represents the 95% confidence intervals. The models were controlled for the average temperature, relative humidity, particulate matter with a median aerometric diameter < 10 microns (PM₁₀), ozone (O₃), time trend, seasonality, day of the week (DOW), and holiday