Water has always been an important and life-sustaining drink for humans and is essential to the survival of most other organisms. More than 3.4 million people die each year from water-, sanitation-, and hygiene-related causes. Nearly all of these deaths (99 percent) occur in the developing world. Next to air (oxygen), water is the most essential element to human life; the human body usually cannot survive longer than one week without it. Water makes up more than two-thirds of the weight of the human body; the brain is 75 percent water, blood is 83 percent water, bones are 22 percent, muscles are 75 percent, and lungs are 90 percent water. About 783 million people, or one in nine people worldwide, lack access to improved sources ...