Pollution refers to the introduction of harmful substances or contaminants into the natural environment, causing adverse effects on ecosystems and human health. Common types include air pollution from vehicle emissions and industrial activities, water pollution from sewage and chemical runoff, soil contamination from improper waste disposal, and noise pollution from traffic and construction. In Canada, pollution control involves all three levels of government: the federal government sets national standards and regulates interprovincial issues, provinces manage industrial permits and environmental assessments, and municipalities handle local matters like wastewater treatment and garbage collection.