Identify one source of pollution within the city centre

Motor vehicles are a HUGE source of pollution in big cities

Cars are because gas and that pollinates the air so if your drive is not that far away you should ride a bike.

Master planned communities outside of chicago. note: population density means people living in an area per square mile. chicago, an urban and highly populated area has a much more higher density than a desert, amish community, settlement, or nomadic region.