How has the air quality of our cities improved due to the state of alarm?

This graph shows how the concentrations of NO2 in the atmosphere of four Basque capitals have been reduced due to the confinement. The stations directed to traffic (blue) and the average of all the stations are analyzed network of measuring stations (green).

All capitals reduce their average NO2 concentration between 40 and 54%. Gasteiz is the least polluted city and the one with the highest accumulated reduction index in the average concentration. It is the second city in population but maintains better air quality than smaller cities like Donostia and Iruña. The Biscayan capital exceeds the WHO recommendations for air quality in those stations oriented to traffic. With the state of alarm, it has reduced its concentrations by 40%. Pamplona is the city that presents the greatest reductions in stations oriented to traffic, up to 45%.