Acid rain is caused by a chemical reaction that begins when compounds like sulphur dioxide and nitrogen oxides are released into the air due to human and natural activities. Acid rain is defined as rain which is made up of water which has lower ph levels as compared to normal rain water. Acid rain is a result of oxides of nitrogen and sulphur which are released into the atmosphere from the surface of earth. Acid rain is harmful for animals, plants, buildings etc. It alters the composition of soil and causes respiratory issues in animals and humans.