This article looks at the effect of six different criteria pollutants and their associated pollution index on the discharge times of respiratory emergency room visits in Mexico City. The analysis is the first to look at the impact of criteria pollutants on the length it takes for patients with respiratory conditions to be cleared out from emergency room status. I infer causality with the use of spatial and temporal panel techniques that control for a broad set of relevant variables and use fixed effects to control for unobservable time consistent and seasonal covariates. In the preferred multipollutant specification, one standard deviation increase in the pollution index, carbon monoxide, fine particle matter, and ozone, leads to increments of 28.1, 22.3, 17.7, and 25.9, percent in the discharge time of respiratory emergency room cases in the city. These results show that environmental policies to reduce pollution can decrease treatment times at emergency rooms, reducing opportunity costs on patients and allowing for a reallocation of resources from pollution triggered to pollution unrelated conditions.