However, when the rate of urbanization exceeds the pace at which the city can support its inhabitants, problems occur. The majority of the world's cities suffer from inadequate sewage facilities, poor drainage, insufficient solid waste disposal and poor air and water quality. These problems are common among cities, and to a great extent the burden of solving them falls on municipal authorities. The Habitat II process is focusing world attention on these challenges and promoting discussion on how to address them. Suggested approaches include development of partnerships between private firms and Governments to solve problems, as well as sharing information on which solutions have worked best, in the hope that they will be adopted in other localities as appropriate.
Water supply is among the most serious problems facing the cities of developing countries.
Problems related to water supply are city-specific, and the challenge for each city will be to understand the unique geographical, topographical and meteorological conditions in which it is placed and to plan accordingly. Most sewage systems, like most water supply systems, were constructed to meet the needs of the colonial populations of the core cities. Because of the rapid growth of cities in developing countries, the challenge will be to meet expanding sewerage needs in the coming decades. In the case of air pollution, problems are always city-specific, reflecting differences in climate, topography and local sources of pollution. Throughout the developing world, air pollution results when the emissions from vehicles, industry and domestic heating and cooking sources exceed the capacity of the cities' natural ventilation systems.