Environment and health

Posted: 26 January 2008

Many of the most serious diseases in cities are 'environmental' because they are transmitted through disease causing agents (pathogens) in the air, water, soil, food, or through insects or animals that are vectors for diseases. Many diseases and disease vectors (for instance the mosquitoes that transmit malaria, dengue fever or yellow fever) thrive when provision for water, sanitation, drainage, garbage collection and health care is inadequate.

  • Around half the urban population in Africa, Asia and Latin America is suffering from one or more of the diseases associated with inadequate provision for water and sanitation.
Map of access to sanitation 2004
Map of access to sanitation 2004
Map showing global access to sanitation 2004. Source WHO and Unicef. Click for full-size image
  • The World Health Organization estimates that more than 600 million urban dwellers live in homes and neighbourhoods with such poor quality housing and lack of basic infrastructure and services that their lives and health are continually at risk.

  • Tens of millions of urban dwellers have no toilet they can use so they either defecate in the open (which is particularly hazardous for women because of the risk of sexual harassment) or in plastic bags (so called "wrap-and-throw").

  • Hundreds of millions have to rely on shared public taps for water to which access is difficult and where the quality of the water is often poor and the supply irregular. Or they rely on water vendors who charge high prices.

  • Improved provision for water and sanitation can bring great benefits in terms of improved health, reduced expenditures (on water vendors and on treatment from diseases) and much reduced physical effort (especially for those who collect and carry water from standpipes or other sources far from their shelters).

Airborne infections

For many, their transmission is aided by the overcrowding and inadequate ventilation that is common in the tenements, boarding houses or small shacks in which most low income urban dwellers live. While improving housing and other environmental conditions can reduce their incidence, medical interventions such as immunization or rapid treatment are more important for reducing their health impact.

Chemicals and physical hazardsSmog affects urban quality of life. Credit: US Environmental Protection Agency

These increase rapidly with urbanization and industrialization. While controlling infectious diseases centres on providing infrastructure and services, reducing chemical and physical hazards is largely achieved by regulating the activities of enterprises and households.

  • Controlling exposure to chemicals in the workplace is particularly important with action needed from large factories down to small "backstreet" workshops. In most cities, there is an urgent need for measures to promote healthy and safe working practices and to penalise employers who contravene them. In many urban areas, domestic indoor air pollution from open fires or poorly vented stoves that use coal or biomass fuels has serious health impacts.

  • There is also a growing need for more effective control of outdoor (ambient) air pollution from industries and motor vehicles. Worldwide, more than 1.5 billion urban dwellers are exposed to levels of ambient air pollution that are above the recommended maximum levels. Urban air pollution problems are particularly pressing in many Indian and Chinese cities.

  • Accidents in the home are often among the most serious causes of injury and premature death, especially where much of the population live in overcrowded accommodation made from temporary (and inflammable) materials and use open fires or unsafe stoves and candles or kerosene lights.

  • Traffic management which protects pedestrians and minimises the risk of motor-vehicle accidents is also important. Motor vehicle accidents have become an increasingly significant contributor to premature deaths and injuries in many cities. The number of fatalities and serious injuries per road vehicle is often much higher in Africa, Asia and Latin American than in Europe.

Managing wastes

Most municipal agencies lack the technical knowledge, institutional competence and funding to provide or contract out waste collection services. In many urban centres, more than a third of the solid wastes generated are not collected and it is usually the low income districts that have the least adequate collection service. In countries, with economies in transition, 75 per cent of solid wastes are disposed of in open dumps. This means that wastes accumulate on open spaces and streets, clogging drains and attracting disease vectors and pests (rats, mosquitoes, flies).

Rubbish dump, Vietnam. Credit: WHOMany industrial and institutional wastes are categorized as 'hazardous' because of the special care needed to dispose of them, keeping them isolated from contact with humans and the natural environment. In most urban centres, governments do little to monitor their production, collection, treatment and disposal. Businesses generally have large incentives to avoid meeting official standards (because they avoid high costs) and little risk in doing so (because regulations are not enforced).

Dealing with disasters

Disasters are considered to be exceptional events which suddenly result in large numbers of people killed or injured or large economic losses. As such, they are distinguished from the environmental hazards discussed above. This distinction has its limitations, since far more urban dwellers die of easily prevented illnesses arising from environmental hazards in their food, water or air than from 'disasters', yet the death toll from disasters gets more media attention.

  • Cyclones and storms have probably caused more deaths in urban areas than other 'natural' disasters in recent decades. Earthquakes and tsunamis have caused many of the biggest urban disasters. Flood disasters affect many more people than cyclones and earthquakes but generally kill fewer people. Landslides, fires, epidemics and industrial accidents are among the other urban disasters that need attention.

  • Global warming will increase the frequency and severity of disasters in many urban areas. For instance, the rise in sea level will increase the risk of flooding for many port cities. It will also disrupt sewers and drains and may bring seawater intrusion into freshwater aquifers. Changes in rainfall regimes may reduce the availability of freshwater resources or bring increased risk of floods.

  • Increasingly, urban authorities recognize the need to integrate 'disaster-prevention' within 'environmental hazard prevention'. The impact of natural disasters can generally be greatly reduced by understanding who within the city population is vulnerable and acting to reduce this vulnerability, before the disaster occurs.

Good governance

Achieving a high quality city environment involves not only reducing environmental hazards, but also providing and protecting those facilities that make urban environments more pleasant, safe and valued by their inhabitants. These include parks, public squares/plazas and provision for children's play and for sport/recreation. This can also be integrated into a concern to protect each city's natural landscapes with important ecological and aesthetic value, for instance wetland areas, riverbanks or coasts.

Here are some basic facts on Governance from the State of the World's Cities Report 2001:

  • 49 per cent of the world's cities have established urban environmental plans.

  • The absolute quantity of local government income varies enormously, with total government revenue per person in cities of highly industrialised countries being 9 times that of cities in the developing world, 39 times that of African cities and 18 times that of Latin American cities.

  • 60 per cent of the world's cities involve civil society in a formal participatory process prior to implementing major public projects.

  • 70 per cent of cities in the world undertake regular independent auditing of municipal accounts. 78 per cent of the world's cities publically announce contracts and tenders for municipal services. 55 per cent of cities have laws that govern disclosure of potential conflict of interest.

The most serious environmental problems in urban areas are largely the result of inadequate or unrepresentative government and inadequate investment. Within city boundaries, the most pressing task for city governments is to reduce environmental hazards - especially those that can be among the most common causes of premature death or serious illness or injury - within a broader commitment to reducing urban poverty and to improving the quality of the urban environment.

Related links:State of the World's Cities Report 2001.Global Environment Outlook 2002 (GEO-3).WHO: Protection of the human environment.

FURTHER READING:Hardoy, Jorge E., Diana Mitlin and David Satterthwaite (2001), Environmental Problems in an Urbanizing World, Earthscan Publications, London.For air pollution and cities, see Elsom, Derek (1996), Smog Alert: Managing Urban Air Quality, Earthscan, London, 226 pages.