What is a “slum”?
UN-Habitat (2016a) defines slums as “contiguous settlements that lack one or more of the following five conditions: 1) access to clean water, 2) access to improved sanitation, 3) sufficient living area that is not overcrowded, 4) durable housing, and 5) secure tenure”. But certainly, “slum” is a simple term for a very complex reality: low-income urban communities vary enormously from one city to another, and within cities. And similarly, the word "slumdweller" is just a short-hand for a complex human reality: evidently, "slumdwellers" are individual women, men and children, each with their own particular aspirations and needs, and their own particular favourite TV show and football team.
How many people live in slums?
The number of “slumdwellers” in the developing world was estimated at 881 million people in 2014, up from 791 million in 2000. So the total number of people living in slums is increasing. The majority of people living in slums are located in three regions: Eastern and South-Eastern Asia (332 million), Central and Southern Asia (197 million) and sub-Saharan Africa (189 million). (UN 2018)
It’s difficult to project how many slumdwellers there will be worldwide in 2030 or 2050. The urban population of the world’s two poorest regions – South Asia and sub-Saharan Africa – is expected to approximately double by 2050. In sub-Saharan Africa, around 60% of the urban population currently lives in slums, and by 2050 the urban population in this region is expected to have increased to 1.2 billion (i.e. 1,200 million): if the slum proportion remains the same, that implies a 2050 slum population of 720 million in sub-Saharan Africa, compared with 201 million in 2014 (UN-Habitat 2016b).
What are the major causes of poor health in slums?
That's a very complex question, and of course it's context-specific. A 2008 study using routine clinical surveillance data from Nairobi slums (Kyobotungi et al. 2008) found that the top 3 causes of death among under-5's were pneumonia, diarrhoeal disease and stillbirth. Among over-5's and adults, the top 3 causes of death were HIV-AIDS/tuberculosis, interpersonal violence and road traffic accidents . But this is just data from one location in 2008, and it can't be generalised. For example, malaria is a major cause of mortality in some locations. Certainly, frequent causes of child mortality and morbidity in slums include diseases associated with poor water and sanitation, with indoor and outdoor air pollution, and with malnutrition.
What basic services do slums require?
Again this is a very complex question, and different slums clearly have different needs and different priorities. From the public health perspective alone, many slum communities urgently need improvements in water supply, in sanitation, in solid waste management, in flood control and drainage, and in healthcare, social care and child nutrition. Ongoing climate change is having multiple impacts, including but not limited to increased frequency of high-intensity rainfall events in some cities, with associated increased risks in flood-prone slum communities. Many slumdwellers need improvements to the build quality of their home, which may be a mere plastic shack. And slumdwellers evidently have multiple other pressing requirements, including for example better transport and livelihoods, better protection against crime, and - fundamentally - tenure security, without which other necessary improvements often can't happen.
UN Habitat (2016a) World Cities Report 2016
UN Habitat (2016b) Slum Almanac 2016
UN (2018) United Nations Department of Economic and Social Affairs, Statistics Division. https://unstats.un.org/sdgs/report/2018/goal-11/
Kyobotungi et al. (2008) The burden of disease profile of residents of Nairobi's slums: results from a demographic surveillance system. Popul Health Metr. 2008;6:1