这座城市的空气污染程度曾高达可接受标准的四倍。

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

《牛津词典》

恶化空气污染程度就是其中一个缺点。

Worsening air pollution is a risk.

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吸烟不仅对健康有害，而且增加空气污染程度。

Smoking cigarettes adds to the general levels of air pollution as well as damaging our health.

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