Air pollution has risen above an acceptable level.

空气污染已经超标。

Air pollution in the city had reached four times the acceptable levels.

这座城市的空气污染程度曾高达可接受标准的四倍。

Cases of breathing difficulties increase in lockstep with air pollution.

呼吸困难的病例随空气污染的加剧而增加。

The new government has yet to grapple with the problem of air pollution.

新政府还需尽力解决空气污染问题。

Do what you can to avoid air pollution.

做一切你能做的以避免空气的污染。