The rapid expansion of cities can cause social and economic problems, such as pollution and traffic problems.

城市的快速发展可能引起社会和经济问题，比如污染和交通问题。

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Exhaust gases from boilers, vehicles, etc., cause air pollution in cities.

锅炉和车辆等排出的废气，污染城市空气。

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Noise Pollution We know the sounds of cities are loud enough to cause great harm to people's hearing in the u.

噪音污染众所周知，在美国，城市巨大的噪音对人们的听力造成了极大的损害。

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Pollution from road traffic, particularly diesel fumes, is the most significant cause of poor air quality in most cities.

BBC: Court reserves UK air quality ruling