Environmental hazards are the main cause of ill-health, injury and premature death in many urban areas. People living in towns and cities in low-income countries face a large number of such hazards. These may be biological (e.g. diseases caused by unclean water and poor sanitation), chemical (e.g. polluted water, indoor and outdoor air pollution from fires, chemicals, industrial processes and vehicles, garbage and hazardous wastes), physical (e.g. fire, floods, landslides, earthquakes, cyclones, extreme temperatures, droughts) and socio-political (e.g. politically organised violence, social tensions and conflicts, criminality and gangs and terrorism). Many such hazards are also present in rural locations, but they can become particularly threatening in built-up and densely populated urban areas.
There is a strong likelihood of major urban disasters in future. For example, many cities around the world (in rich as well as poor countries) are sited in earthquake zones or along coastlines exposed to cyclones and tsunamis; or, as they grow, they expand into hazard-prone areas such as floodplains, deserts and hillsides. Urban growth can also threaten ecosystems that contribute to resilience. Earthquakes in large urban centres have been responsible for some of the greatest disasters in recent times, in both low- and high-income countries: the earthquake in Haiti in 2010 killed more than 220,000 people; damage resulting from the 1995 Kobe earthquake in Japan amounted to over $100bn.+EM-DAT database: http://www.emdat.be. Flooding is a major hazard in many cities: in the Indonesian capital Jakarta, floods in January 2013 displaced more than 14,000 people, some for weeks, and damage to homes and business disruption cost an estimated $1bn.
+J. Taylor, When Non-climate Urban Policies Contribute to Building Urban Resilience to Climate Change: Lessons Learned from Indonesian Cities (London: IIED, 2013), http://pubs.iied.org/pdfs/10630IIED.pdf. Even where fatalities are low, the economic and social impact of a hazard may be considerable. For example, in 2009, when four coastal municipalities in Colombia were flooded, there were only two fatalities and 20 people reported missing, but more than 25,000 were displaced; 1,125 houses were destroyed (along with schools, health centres and roads) and 1,400 damaged.+D. Dodman et al., Understanding the Nature and Scale of Urban Risk in Low- and Middle-income Countries and Its Implications for Humanitarian Preparedness, Planning and Response (London: IIED, 2013), http://pubs.iied.org/pdfs/10624IIED.pdf.
Frequent, smaller-scale hazard events such as fires and industrial and road accidents can have a considerable cumulative impact on wellbeing and livelihoods in high-density urban settlements, where there may also be particularly acute public health problems arising from pollution and inadequate sanitation, together with risks from high levels of violence and crime. These smaller events do not feature in many disaster datasets and so tend to go unnoticed by decision-makers and have a low priority in disaster planning. In some rapidly growing cities there is growing concern about water scarcity, and outdoor air pollution, particularly in high-altitude cities, can present problems, notably for the elderly and children.
Cities also tend to be much warmer than the surrounding countryside, and night-time cooling is lower than in rural areas. This ‘heat island’ effect is caused by the concentration of large heat-retaining structures, asphalt and concrete landscapes, physical obstruction of cooling breezes by buildings and heat produced by industrial and domestic activities. Many cities are not designed to deal with this problem. Ventilation and heat management are rarely considered seriously in urban development or taken into account in emergency planning, even in high-income countries.