Almost a seventh of China has been under heavy smog.

中国近七分之一的地区一直处于重度雾霾之下。

youdao

The sky over the city was overspread with heavy smog.

城市上空罩上了一层浓重的烟雾。

youdao

The sky over the city was overspread with a heavy smog.

城市上空罩上了一层烟雾。

《新英汉大辞典》

Days of heavy smog in New York City so thick that people actually were dying from being unable to breathe the air.

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Smog also spread across central and eastern regions as a yellow haze alert was issued yesterday, and "heavy to severely heavy pollution" was recorded in Beijing, China Daily reports.

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