|Basic Facts on Urbanization (HABITAT, 2001, 21 p.)|
As a consequence of the expansion of urban areas humankind is exposing itself to increased environmental deterioration. Among the most serious of these are air, water or noise pollution, as well as the problems related to the exposure to solid wastes (including toxic and hazardous wastes). Many urban areas are also at risk from natural hazards or hazards whose origin may be natural but where the level of risk and the number of people at risk is much increased by human actions, such as floods, landslides, etc. Because the poor are forced to live in the most marginal areas of cities, the poor have to bear the brunt of the effects of environmental deterioration.
Most air pollution in urban areas comes from the combustion of fossil fuels - in industrial processes, for heating and electricity generation, and by motor vehicles. As the use of fossil fuels in each of these processes tends to increase with economic growth, so too does air pollution - unless measures are taken to promote efficient fuel use while the use of the most polluting fuels (such as coal, and leaded petrol) is discouraged. It is estimated that 1.4 billion urban residents worldwide are exposed to annual averages for suspended particulate matter or sulphur dioxide (or both) that are higher than the recommended WHO standards.(44)
Poorly managed cities and towns contribute to unsustainable production and consumption patterns. They also generate unmanageable wastes which harm land and water resources as well as the atmosphere. Sustaining healthy environments in the urbanized world of the twenty-first century represents a major challenge for human settlements development and management.
The scale of the problem of hazardous wastes and the potential risk to people's health has only been recognized in the last 20 years. Many industrial countries face a large and expensive backlog of clearing up toxic or otherwise hazardous wastes that were dumped on land sites with inadequate provision for their safe storage.
The sheer size of many cities has led to a situation in which they have outgrown the capacity of their neighbouring region to provide adequate and sustainable water supplies. Many cities are currently living on borrowed time, consuming more water than the local ecosystem can sustain.