The Environment and Health - Water pollution

To an increasing extent, water pollution has prevented or limited use of many once-valuable sources of water. This progressive deterioration of the nation's water supply has resulted from years of abuse in which natural lakes and waterways were inundated with quantities of raw sewage, waste products of industrial plants and slaughterhouses, petroleum residues, poisonous herbicides and insecticides, and so on. But the pollutants generally fall into two categories: materials that change with time and contact with water, and materials that remain unchanged in form. Organic materials in sewage and such industrial wastes as pulp and paper effluents belong in the first group; inorganic salts like sodium sulfate and such inert inorganic materials as pesticides represent the second.

Communities generate thousands of tons of municipal sewage daily. Industries, the greatest users of water, utilize more than half of all the water consumed in the United States for raw material, heating and cooling processes, and transporting, sorting, and washing operations. Agriculture, the second largest user, requires millions of gallons of water for irrigation and drainage; for spraying orchards and crops, often with insecticides, fungicides, or herbicides; for removal of animal and other organic wastes; and for manufacturing operations such as meat packing and canning.