ABSTRACT
Air pollution can result from natural sources, and the resulting pollutants can have much more severe and long-lasting effects than air pollution from human activities. Air pollutants can be classified as either primary or secondary air pollutants. This chapter focuses on ambient air pollutants but point out that indoor air pollution is beginning to receive the attention it merits. At the present, two types of ambient air pollutants are regulated under the Clean Air Act (CAA): criteria and hazardous air pollutants. Many air pollution problems have been recognized, ranging from small areas affected by a single industry to citywide problems caused by multiple contaminants to global-scale contamination by universal pollutants. In recent decades, scientists have speculated that various air pollutants have caused the atmosphere to absorb more heat. At the local level, with air pollution, the greenhouse effect causes heat islands in and around urban centers, a widely recognized phenomenon. Chlorofluorocarbons (CFCs) have been blamed for air pollution problems.
