This dry air leads to increased tracheal irritation and secretion production.

这种干燥的空气会增加气管刺激和分泌物的产生。

The dirty air led many people walking or working outside to wear face masks and at least two universities cancelled classes.

空气污染导致很多在户外走路或者工作的人要带上面罩，至少已经有2所大学停课。