Why do you think lichens are not commonly found in cities where are pollution is big problem?

Lichens are sensitive to air pollution, particularly sulfur dioxide and nitrogen oxides, which can inhibit their growth and survival. In urban areas with high levels of pollution, the harsh chemical environment can damage their delicate structures and interfere with their ability to photosynthesize. Additionally, the lack of suitable substrates and the disturbance of natural habitats in cities further limit their presence. As a result, lichens are often more abundant in cleaner, less disturbed environments.