The U.N. predicts that in the next few years the largest cities will be found in China, India, the U.S. and Japan. Increasing urbanization usually leads to a disparity between socio-economic classes. The urban lifestyle is a major health risk. Air pollution accounts for an increasing number of health problems. Accumulation of industry in and around urban areas as well as traffic are a major source of this pollution.
Smog correlates to an increase in asthma and other respiratory diseases.
The stress of urban life increases the risks of cardiovascular disease - not to mention higher crime rates and increases in traffic accidents. In response to the drawbacks of urban life, a few countries such as Australia, the U.K. and Sweden, the current trend is de-urbanization. In developed economies, rural populations are experiencing larger population growth than the cities. This reversal has been sparked by a change in social values and an increase in self-employment. Deurbanization is aided by modern communication that allows people to work out of their own homes.