短语讲解：
1. Highways in these regions were temporarily shut down, and police urged drivers to reduce their speed in the thick fog.
shut down完全关闭，倒闭，停止运转
例句：The shop has shut down because of lack of trade.
那商店因生意萧条而停业。
2. Hundreds of flights across the country were cancelled or delayed due to low visibility.
due to由于，因为
例句：Her absence is due to illness.
她因病缺席。
3. They may have a noticeable impact on our respiratory system especially for people with chronic respiratory diseases.
have an impact on对…有影响;对…起作用,产生效果
例句：The computer has a great impact
