Well, I guess air pollution is the most serious. The sky is not blue any longer. Instead, it's always gray. You will have difficulty in breathing?

呃，我想空气污染是最严重的。天空不再是蓝色的，反而总是灰蒙蒙的。你呼吸的时候会有困难。

youdao

I get phlegm in my throat and have difficulty in breathing.

我喉咙有痰而且呼吸困难。

youdao