Oxygen and water are essential elements for the proper functioning of the body. Water usually contains anywhere between 1 to 10 ppm (parts per million) of dissolved oxygen. Ponds usually contain the lowest amount. Streams and rivers usually have the highest amount. Tap water in most large cities is usually around 5-7 ppm of dissolved oxygen. Oxygenated water contains approximately 200,000 ppm.

The air you breathe is 15% to 20% oxygen. In some major cities, the oxygen content can be as low as 9%. An inadequate supply of oxygen is called "hypoxia" and may cause symptoms such as: