Air pollution threatens our health, environment, and climate. The sources of air pollution are numerous anthropogenic and natural emissions; some are pollution in their own right, and some trigger the formation of secondary pollution. Detailed knowledge of the sources of pollution and the transformations of pollution in the atmosphere is the best possible basis for effective and cost-effective management strategies. While this knowledge is the basis of environmental management as regards emissions standards and best-practice pollution control systems, it is also critically important to society as it seeks to adopt policies and behaviors to reduce air pollution and its associated impacts and direct resources toward research and technological development to achieve sustainability. In fact, reducing air pollution emissions and thereby improving air quality will help us to meet a series of United Nations Sustainable Development Goals. Environmental pollution contributes to poverty, low crop yields, and disease, and the fight for resources leads to political instability. Thus, reducing air pollution helps us achieve sustainability by reducing poverty and inequality, providing jobs in the clean technology sector, and reducing and overcoming climate change. During the 2020 Corona crises, air pollution levels have decreased substantially in urban areas around the world because of reduced travel and industrial activity. These improvements

in air quality have made real some of the improvements that can be obtained from, e.g., moving towards a society less dependent on fossil fuels. Improved cleaning technologies are the result of both pull and push strategies. This can be seen in the vehicle industry where strict emission standards have forced manufacturers to develop new technologies. These developments have been important for improving air quality in many parts of the world over the past two to three decades.