Many of the world’s social and environmental problems are concentrated in cities. At least 220 million people in cities in the developing world lack clean drinking water, 420 million lack basic sanitation, 600 million lack adequate housing, and over 1 billion suffer severe air pollution. China alone reported 3 million deaths from air pollution between 1994 and 1996; children in Mexico city, Beijing, Shanghai, Tehran, and Calcutta inhale the equivalent of two packs of cigarettes per day. Patterns of water, waste, food, energy, transportation, and land use in urban areas are critical determinants of the balance between human activities and the environment.
