The study looked at how pollution from NO2 in Indian cities changes as the economy grows. They found that in some areas, as income goes up, pollution goes down, but in others, pollution keeps increasing. This suggests that economic policies can affect the environment. The researchers analyzed data from 139 cities between 2001-2013, focusing on residential and industrial areas as well as low, medium, and high-income areas. The results show that different areas have different patterns of pollution levels with economic growth. This means that policy decisions can play a role in reducing pollution in cities.