3 sentences

1. 二氧化硫是一种常见的空气污染物。

   èr​yǎng​huà​liú shì yī zhǒng cháng​jiàn de kōng​qì wū​rǎn​wù.

   Sulfur dioxide is a common air pollutant.

   Source: Dong Chinese Dictionary

2. 由于空气污染严重，该地区的空气质量较差。

   yóu​yú kōng​qì wū​rǎn yán​zhòng, gāi dì​qū de kōng​qì zhì​liàng jiào​chà.

   Due to severe air pollution, the air quality in the region is relatively poor.

   Source: Dong Chinese Dictionary

3. 汽车尾气排放是城市空气污染的主要来源之一。

   qì​chē wěi​qì pái​fàng shì chéng​shì kōng​qì wū​rǎn de zhǔ​yào lái​yuán zhī​yī.

   Vehicle exhaust is one of the main sources of urban air pollution.

   Source: Dong Chinese Dictionary