sewer gas

例句：

1. 1.The sewer gas was so bad that it made the workers sick.
   下水道气体太浓了，让工人们生病了。
2. 2.The sewer gas is a major source of pollution in many cities.
   下水道气体是许多城市的主要污染源。
3. 3. The sewer gas is harmful to human health, and must be treated before being released into the environment.
   下水道气体对人类健康有害，必须在排放到环境中之前进行处理。