The document defines air pollution as particles or gases found in air that are not part of its normal composition, including natural sources like forest fires and unnatural sources from burning fossil fuels. It describes the Air Quality Index scale of 0-500 that indicates health risks from pollutant levels. The five major pollutants are outlined as carbon monoxide, sulfur dioxide, nitrogen dioxide, particulate matter, and ground-level ozone. Smog is defined as a combination of gases, water vapor, and dust formed from vehicle and industrial emissions reacting with heat and sunlight. Ways to reduce air pollution include choosing active transportation, encouraging emission inspections, and conserving energy.