Water is also a carrier of disease. Most U.S. cities have deteriorating waste water treatment and distribution systems with completely inadequate programs for replacement or upgrade. Since the United States is one of the fastest growing industrial countries, municipal systems will be further strained. Previously unrecognized waterborne pathogens, such as Cryptosporidium, already have emerged. In the developing world, where 98 percent of population growth now takes place and is projected to take place, squalid urban slums are already crowded with an unprecedented number of displaced people living in conditions favorable to the rapid spread of disease.
Water is essential for all living things.
Competition for water and, in some cases, food is becoming more intense. Human population is expected to reach six billion people this October, an increase of one billion in 12 years, and three billion or a doubling of world population since mid-century. Over one billion will be adolescents, just entering their reproductive years. Already, more than one billion people in developing countries do not have access to safe drinking water and more than 2.5 billion lack basic sanitation, according to the United Nations Development Program. Water is also a carrier of disease.