2 sentences

1. 工厂排放的废气严重污染了大气。

   gōng​chǎng pái​fàng de fèi​qì yán​zhòng wū​rǎn le dà​qì.

   Exhaust gas emitted by factories seriously pollutes the atmosphere.

   Source: Dong Chinese Dictionary

2. 工厂必须减少废气排放以保护环境。

   gōng​chǎng bì​xū jiǎn​shǎo fèi​qì pái​fàng yǐ bǎo​hù huán​jìng.

   Factories must reduce exhaust emissions to protect the environment.

   Source: Dong Chinese Dictionary