Against the background of the global COVID-19 outbreak and the increasing number of confirmed infections Europe, a shutdown of all non-essential businesses took place. Besides lower emissions from industries the amount of traffic declined significantly, especially in regions with a high commuter amounts. Traffic is an important source of fine particles, and due to their size and chemical composition they pose a high risk to human health. On a global scale PM has led to >3.3 million premature deaths and has been associated with diseases like acute lower respiratory illness or COPD. Furtherm...