Which of the following is a potential environmental concern with bus idling?

Bus idling presents a significant concern for air quality degradation. When buses idle, they emit pollutants such as nitrogen oxides, carbon monoxide, and particulate matter, which can contribute to poor air quality. This is especially critical in urban areas where air pollution levels can already be elevated due to a concentration of vehicles and activity. Prolonged exposure to these emissions can negatively impact the health of individuals, particularly vulnerable populations such as children and the elderly, as well as contribute to broader environmental issues like smog formation and climate change.

In contrast, while noise pollution from idling buses can be an issue, it does not have the same level of widespread environmental impact compared to air quality concerns. Traffic congestion and fuel efficiency are also relevant discussions but are not direct environmental concerns associated specifically with the effects of bus idling on air quality. Therefore, the focus on air quality degradation highlights the most significant environmental impact associated with idling buses.