Pollution is defined as the introduction of harmful materials into the environment. Pollutants can be natural, like volcanic ash, or created by human activity through trash, factory runoff, and other sources. The main types of pollution are water, land, air, and noise pollution. Water pollution contaminates water supplies chemically or with hazardous substances. Land pollution deteriorates land and groundwater through solid and liquid waste accumulation. Air pollution modifies the atmosphere through vehicle emissions, manufacturing, power generation, and chemical production. Noise pollution is unwanted disturbing sound that affects human and animal health from sources like vehicles, appliances, and industrial machines.