Fig. 3From: Association and interaction of O3 and NO2 with emergency room visits for respiratory diseases in Beijing, China: a time-series studyThe interaction of O3 and NO2 on emergency room visits for respiratory diseases. A Effect of O3 under different NO2 levels; (B) Effect of NO2 under different O3 levels. NO2 or O3 concentrations were classified as low, medium, and high levels according to their 25% and 75% quartiles. NOTE: O3, ozone; NO2, nitrogen dioxide; TRD, total respiratory disease; AURI, acute upper respiratory infection; LRTI, lower respiratory tract infectionBack to article page