Sulfur dioxide released by burning fuels rises into the atmosphere. It dissolves in the water droplets in clouds and forms an acidic solution. When this falls it is called acid rain, which is more acidic than normal rain.
Acid rain causes several problems. Buildings and statues made from limestone or marble, which are forms of calcium carbonate, are damaged because carbonates react with acid. Metal structures such as bridges and railings corrode faster. Lakes and rivers become acidic, which kills fish and other water life.
Acid rain also damages the leaves of trees and washes nutrients out of the soil, so trees can die. Sulfur dioxide gas itself can cause breathing problems such as asthma.