What is smog? 什么是烟雾？

　　It is fog combine with dirt and dust in the air. 它是雾与空气中的粉尘相结合的混合物。

　　Is it a natural event? No, it isn't. 它自然事件吗？不是。

　　In fact, smog is a type of air pollution. 烟雾实际上是空气污染。

　　In big cities, smoke from automobiles and factories goes up into the sky and meets the moisture in the air. 在大城市，汽车和工厂排放的废气上升到空中并与空气中的湿气相遇。

　　When the air cools down at dawn, a huge amount of the dirty moisture in the sky comes near the ground. 拂晓时分空气温度下降，空中大量肮脏的湿气接近地面。

　　And what happens? 然后会发生什么？

　　It forms smog. 它会形成烟雾。

　　Smog is a huge problem to people in big cities. 烟雾是大城市居民面临的重大问题。

　　Smog causes many kinds of lung diseases and eye or nose problems. 烟雾会引发各种肺病和眼鼻问题。