The 21st century health challenge of slums and cities

2Starting in 2007, and for the first time in human history, the majority of the world’s population will live in urban areas. According to the latest UN projections, 3 by 2030, the world’s urban population will increase by more than two billion, while the rural population will decline by about 20 million. This shift is largely the culmination of a rapid global urbanisation process that has been underway for more than 250 years. Rapid urbanisation first became manifest in the countries undergoing industrialisation in the developed world, and then in Latin America. Today its prime locus is the poorer parts of Asia and Africa. More than 90% of the world’s urban population growth by 2030 will be in less developed regions. Any effort to measurably improve global health outcomes, especially in these regions, will need to address urban reform. According to estimates prepared by the UN Human Settlements Programme (UN-HABITAT), about a third of the world’s estimated 3 billion current urban residents dwell in slums, or places characterised by one or more of these shortcomings: insecurity of tenure, poor structural housing conditions, deficient access to safe drinking water and sanitation, and severe overcrowding. 4 All these factors have direct