What are the major types and sources of air pollution?
Air pollution is the presence of one or more chemicals in the atmosphere in quantities and duration that cause harm to humans, other forms of life, and materials. As clean air in the troposphere moves across the earth’s surface, it collects the products of natural events (dust storms and volcanic eruptions) and human activities (emissions from cars and smokestacks). Theses potential pollutants, called primary pollutants, are mixed vertically and horizontally and are dispersed and diluted by the churning air in the troposphere. While in the troposphere, some of these primary pollutants may react with another or with the basic components of air to form new pollutants, called secondary pollutants. Long-lived primary and secondary pollutants can travel great distances before they return to the earth’s surface as solid particles, droplets, or chemicals dissolved in precipitation. Most pollutants in urban areas enter the atmosphere from the burning of fossil fuels in both power plants and fa
