In order to manage the corona pandemic, the number of aircraft movements was reduced worldwide. Before the Federal Council's decided to release the first relaxation measures, only 10% of scheduled flights took off at the end of April at Zurich Airport. But road traffic also fell sharply in the Zurich region: a reduction in traffic flow of 50-80% was observed in the entire Zurich economic area (WRZ). In the knowledge that road traffic is responsible for a large proportion (>50%) of nitrogen oxide (NOx) emissions and that aviation, although locally limited, also emits a high proportion of fine particulate matter (non-volatile and volatile nanoparticles), greater positive effects of the COVID lockdown on air quality can be expected. The Meteorology, Environment and Aviation Research Unit of the Center for Aviation was able to detect an astonishingly low particle concentration in calendar week 16 by means of initial air hygiene measurements carried out immediately adjacent to the airport. Initial internal and external reports also indicate that certain pollutant concentrations have decreased significantly. In addition, on the initiative of some of the project participants listed above, 10 measuring instruments for respirable particles (LDSA) were installed in the central WRZ in calendar week 18 in cooperation with naneos AG, the City of Zurich (UGZ) and AWEL.There are thus two data streams: On the one hand, automatic measuring stations of the Ostluft and NABEL networks recorded the entire COVID episode, while on the other hand the COVID lockdown triggered specific measuring campaigns. Both data streams will be used to achieve an initial quantification of the "COVID 19 effect" (CE). However, this step is difficult: air pollutants, such as PM10, can be transported over global scales and thus distort local effects very strongly. In order to analyse the CE in detail, model-based statistical methods are required, which - if necessary - also take into account the stochastic part of the temporal and spatial correlation, which is why the IDP will contribute to this project as a statistical consultancy.