Many scientists believe that air pollution is a contributing factor to this mortality. Pollutants may cause physiological changes in trees that lessen their resistance to diseases and to damage from freezing. There is, however, little direct evidence linking acid rain to forest dieback. Scientists do agree that acid rain can lead to other, less extreme effects on soil and forest systems. It can leach nutrients from soil and foliage while inhibiting photosynthesis.
Acid rain can also kill certain essential microorganisms.
The toxic metals it mobilizes when passing through the soil can be harmful not just to aquatic life, but to trees and crops as well. The problem is far more than aesthetic. Building materials, too, can be degraded by acidity. Limestone, marble, carbonate-based paints, and galvanized steel all are eroded and weakened by the kind of dilute acids found in acid deposition. The Acropolis in Greece, the Coliseum in Italy, and the United States Capitol building, all are deteriorating due to the effects of air pollution.