In October 2019, the Flemish Government approved the Air Policy Plan 2030 (Departement Omgeving, 2019). This plan contains measures to tackle air pollution in Flanders. In this way, the impact of air pollution on our health and the living environment can be reduced. One part of the Air Policy Plan deals with air pollution by nitrogen compounds. In this report, we examine the evolution of these components over time. More specifically, we look at three phases in the chain: the emission, the quantity in the air (atmospheric concentration) and deposition in the environment.