Recently, as developed countries, many cities have become more suitable for living with all the services people need for a comfortable lifestyle. Therefore, many people migrate from rural areas to urban areas in a process called urbanization (Wikipedia, 2009). Urbanization has become one of the most important issues facing both people and governments in most countries. An important term that has been suggested as a policy to solve the problems associated with urbanization is sustainable development. Sustainable development could be defined as a balance between human needs and environmental protection (Wikipedia, 2009). This essay aims to examine the problems of urbanization and discuss how sustainable development policy can be a good solution for this. Furthermore, the essay will briefly focus on three main points: overcrowding, traffic congestion and air pollution. First, as people have moved into cities in large numbers, cities become overcrowded. This consequence can lead to many problems, including casual life and health problems. A great example of overcrowding is found in Mexico City. Population growth in the city is estimated to exceed 10,000 people/sq km, and this number has increased due to huge movements within the city (Bilham-Boult et all, 1999. pp2). To imagine the situation in Mexico City, Bilham-Boult also cited "the crowded, polluted and chaotic city." Regarding health issues, infectious diseases can spread between individuals, particularly in areas containing large numbers of people. A good example of this can be seen simply in the transition of the tuberculosis pathogen, which can be inhaled...... middle of paper ......xford: Heinemann.Greenwood, D., Slack, R. , Peutherer, J. and Barer, M. (2007) Medical Microbiology, United States: Elsevier.Thisdell, D. (1993). Can LA kick the car habit? New Scientist, 138 (1887), 24-29.BBC. 25 May 2007 City congestion charge plan unveiled http://news.bbc.co.uk/1/hi/england/manchester/6691683.stm Viewed 21-07-2009 Stephen J. Gislason (2009) Cars, Air Pollution and Salutehttp://www.nutramed.com/environment/cars.htm Viewed 07-26-2009Wikipedia Encyclopedia. July 26, 2009 Urbanizationhttp://en.wikipedia.org/wiki/Urbanization. Viewed on 07-20-2009Wikipedia encyclopedia. July 23, 2009 Sustainable developmenthttp://en.wikipedia.org/wiki/Sustainable_development. Viewed on 07-20-2009Wikipedia encyclopedia. July 14, 2009 Traffic Congestionhttp://en.wikipedia.org/wiki/Traffic_congestion. Seen in 23-07-2009