What are acid rains?

What are acid rains? Acid rain is another side-effect of civilization. As soon as acid rain was discovered and understood, it was attributed to human action. (Jurgen Stock, Arthur R. Upgren, p.4)Acid rain can be called every atmospheric precipitate (rain, snow, smog, rain with snows, etc) which has the following characteristics the increased level of acids (mainly sulphuric acid) and the hydrogenous index of pH is little than average index of rain water (average pH for rain water is 5.6), mainly it is rain with pH