Air pollution is defined as the presence of toxic chemicals or compounds in the air at levels that pose health risks. Major causes of air pollution include the burning of fossil fuels which emits sulfur dioxide and carbon monoxide, agricultural activities which release ammonia, and exhaust from factories and industries containing hydrocarbons and organic compounds. Effects of air pollution include respiratory and heart problems, global warming, acid rain, and depletion of the ozone layer. Prevention of air pollution can be achieved through using public transportation, conserving energy, reducing waste, emphasizing clean energy sources, and using energy efficient devices.