What are the effects of acid deposition?
Risk analysis experts rate acid deposition as a medium-risk ecological problem and a high risk to human health. Acid deposition has many harmful ecological effects, especially when the pH falls below 5.1 for terrestrial systems and below 5.5 for aquatic systems. It also contributes to human respiratory diseases such as bronchitis and asthma (which can cause premature death), and it damages statues, buildings, metals, and car finishes. Acid deposition and other air pollutants such as ozone (O3) can damage tree foliage directly, but the most serious effect is weakening trees so they become more susceptible to other types of damage. The areas hardest hit by acid deposition are mountaintop forests, which tend to have thin soils without much buffering capacity. Trees on mountaintops, especially conifers such as red spruce that keep their leaves year-round, are bathed almost continuously in very acidic fog and clouds. A combination of acid deposition and other air pollutants (especially ozon
