Pollution is the contamination of air, soil, or water by the discharge of harmful substances.
Pollution prevention occurs when raw materials, water, energy and other resources are utilized more efficiently, when less harmful substances are substituted for hazardous ones, and when toxic substances are eliminated from the production process. By reducing the use and production of hazardous substances, and by operating more efficiently we protect human health, strengthen our economic well-being, and preserve the environment. Source reduction allows for the greatest and quickest improvements in environmental protection by avoiding the generation of waste and harmful emissions. Many times this can result in the transfer of pollution from one medium to another. For example, in some cases, by requiring hazardous air emission controls for industrial facilities, other problems might result, such as pollutants being transferred to underground drinking water through the residual sludge.