smog

n. 烟雾

Smog hung in the sky (over the city).

（城市）上空烟雾弥漫.

On the night of December1, 1930, a cloud of smog moved over a valley in Belgium, which caused thousands of people to become ill.

1930年12月1日晚上，一片烟雾飘过比利时的一个山谷，这使数千人病倒了。