Most of us in developed countries take clean and plentiful water as a given, not just drinking water, but water for many household, yard, and other uses. Yet, says the American Academy of Microbiology, “Microbiologically safe drinking water can no longer be assumed, even in the United States and other developed countries, and the situation will worsen unless measures are taken in the immediate future – the crisis is global.” Treating drinking water to kill pathogens is given much credit for increasing the life span of US citizens, from 47 years at the turn of the twentieth century to 77 years. But the twenty-first century begins with one-fifth of the world's humanity still without clean drinking water. Even poor-quality water is becoming scarcer because ever-increasing numbers of people live in areas of water scarcity in which not only is drinking water a problem, but also water for sanitary needs. Within 10 to 15 years the United Nations estimates that at least 40% of the world's people will live in countries where they cannot get enough water to satisfy basic needs. Wildlife is increasingly deprived of water. Domestic animals may go wanting too. Demand for fresh water increased six-fold in the twentieth century, more than twice the rate of population growth. Reasons for water scarcity include increasing human populations that need and want ever-more water. Industrial use of water has increased too.