Reduction in Visibility
Sulfates and nitrates in the air contribute to reduced visibility, which means that people cannot see clearly or as far through the air. The air looks "hazy." Sulfate particles account for 50% to 70% of the visibility reduction in the eastern United States. Visibility in the East was expected to improve by 30% by 2010 because of acid rain program controls. The EPA has projected that this improvement will be worth more than $1 billion per year to the tourist industry in and around the eastern national parks.
In the western states, sulfates, nitrates, and carbon all play roles in reduced visibility. Sulfates have been shown to be important contributors to reduced visibility in many of the national parks found on the Colorado Plateau. These include Bryce Canyon, Grand Canyon, and Canyonlands. On the other hand, increased particulate in the air contributes to the spectacular sunrises and sunsets in the Red Rock country.
Human-Made Objects
Limestone and marble turn to gypsum, a crumbling substance, when exposed to acid. Many of the world's most beautiful buildings, monuments, and statuary are composed of these materials. Throughout the world, important art treasures and cultural and historic sites, such as the Taj Mahal in India; the Colosseum in Rome, Italy; and the Lincoln Memorial in Washington, D.C., are at risk. (See Figure 9.4.)
Investigations into the effects of acid rain on human-made objects in the United States, such as buildings, statues, metals, and paints, began only in the 1990s. A joint study conducted by the EPA, the Brookhaven National Laboratory, and the Army Corps of Engineers in 1993 found that acid rain caused $5 billion worth of damage annually in a seventeen-state region. Two-thirds of the damage was created by pollution whose source was less than thirty miles away.
New kinds of protective chemicals called consolidants, which adhere to limestone and marble, are being used to save some of the world's decomposing monuments from acid rain and other pollutants. Consolidants were developed in the 1960s in response to widespread water damage to stone buildings in Venice, Italy. Experts reported, however, that these chemicals have many limitations. They are toxic and difficult to apply. Their effects are only temporary, yet they permanently alter the nature of the stone. Most important, their long-term effects are uncertain. For those reasons, their use was banned on the Acropolis in Athens, Greece.
Automotive Coatings
During the 1990s, reports of damage to automotive textured roofs and paints increased. The damage generally occurs on flat, horizontal surfaces and appears as permanently etched, irregularly shaped areas. The damage is most easily observed on dark-hued vehicles, and can be detected with the aid of fluorescent lights on many vehicles that show no signs visible to the naked eye. Usually the damage is permanent.
The general consensus within the automobile industry is that the damage is caused by some form of environmental fallout. In the auto industry, the term "environmental fallout" refers to a wide variety of happenings, including bird droppings, decaying insects, acid rain, and tree sap. Chemical analysis of the damaged areas of some car finishes, however, has shown elevated levels of sulfate, implicating acid rain.
Quantifying the contribution of acid rain to paint finish damage relative to other forms of environmental fallout, deficient paint formulas, or improper paint application has been difficult. The best way to determine the exact cause of the damage is chemical testing, an expensive proposition.
The auto industry is actively pursuing the development of coatings that are more resistant to acid rain and other environmental fallout. Until acid rain is controlled or a universal protective technology is developed, the best protection for a vehicle is to keep it covered during precipitation events and wash it frequently, followed by hand drying.
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