What major environmental issue is often associated with urban areas?

Air pollution is a major environmental issue commonly associated with urban areas due to the dense concentration of vehicles, industrial facilities, and energy consumption that characterizes cities. Urban environments tend to have higher levels of particulate matter, nitrogen oxides, and other pollutants that arise from transportation, construction activities, and the burning of fossil fuels. Moreover, the built environment, combined with limited green spaces, exacerbates the problem as natural filtration systems are reduced, leading to poor air quality that can have significant health impacts on urban populations.

In contrast, while sustainability encompasses various environmental goals, it is more of a broad concept rather than a specific issue directly tied to urban areas. Deforestation primarily occurs in rural or tropical regions and is more associated with land use changes for agriculture and logging, rather than being a typical concern of urban settings. Soil erosion, while an environmental concern, also tends to relate more to rural land management and agricultural practices rather than the concentrated areas of habitation found in urban centers. Thus, air pollution stands out as the most pressing urban environmental challenge.