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Human health is increasingly determined by environmental conditions (Rapport and others 1999, McMichael 2001). According to a report from the World Health Organization (WHO 1997), for example:

  • Deteriorating environmental conditions are a major contributory factor to poor health and poor quality of life. Mismanagement of natural resources, excessive waste production and associated environmental conditions that affect health pose major challenges to sustainable development.
  • Impoverished populations living in rural and periurban areas are at greatest risk from degraded environmental conditions. The cumulative effects of inadequate and hazardous shelter, overcrowding, lack of water supply and sanitation, unsafe food, air and water pollution, and high accident rates, have serious effects on the health of these vulnerable groups.
  • Poor environmental quality is directly responsible for some 25 per cent of all preventable ill health, with diarrhoeal diseases and acute respiratory infections heading the list.
  • Two-thirds of all preventable ill health due to environmental conditions occurs among children.
  • Air pollution is a major contributor to a number of diseases, and to a lowering of the quality of life in general.

There are regional differences in the way human health is vulnerable to environmental degradation. Communities in many parts of Central and South America, Central Africa and Asia are highly vulnerable to water-borne and vector-borne diseases. Air pollution threatens large urban areas and mega-cities, most of which are in developing countries. People in developed countries are more vulnerable to exposure to toxic chemicals and technological accidents but there are notable exceptions such as arsenic contamination in south Asia (see box).

Arsenic contamination in Bangladesh
In Bangladesh, naturally occurring arsenic in underground sediment leaches into the groundwater. More than 25 per cent of the 4 million tube wells that are the main source of drinking water contain dangerous levels of arsenic. Nearly 75 million people are vulnerable to arsenic poisoning which can cause skin cancer, kidney and liver failure, respiratory problems and death. About 24 million people have already been exposed to arsenic poisoning. Agricultural production is affected by arsenic-contaminated water in a 500-km swath of rice paddies and banana groves between the Ganges River and the Indian border.
Sources: Karim 2000, BICN 2001a and 2001b, and UN Wire 2001

Overall, it is estimated that 25-33 per cent of the global burden of disease is attributable to environmental factors (Smith, Corvalán and Kjellström 1999). Recent estimates suggest that environment-related premature death and illness account for 18 per cent of the total burden of disease in the developing world (Murray and Lopez 1996). This comprises contributions from water supply and sanitation (7 per cent), indoor air pollution (4 per cent), vector-borne diseases (3 per cent), urban air pollution (2 per cent) and agro-industrial waste (1 per cent). In sub-Saharan Africa the figure is even higher at 26.5 per cent, mainly related to water supply and sanitation (10 per cent) and vector-borne diseases (9 per cent).

Satellite image shows extensive smoke haze over Indonesia and neighbouring areas on 20 October 1997. Hot spots are probable areas of forest fires. Smoke haze had severe effects on the health of people over a wide area of Southeast Asia

Source: Meteorological Service of Singapore 2002

Globally, 7 per cent of all deaths and diseases are due to inadequate water, sanitation and hygiene (UNDP, UNEP, World Bank and WRI 1998). Approximately 5 per cent are attributable to air pollution (Holdren and Smith 2000). Every year, environmental hazards kill 3 million children under the age of five (WHO 2002). Current estimates suggest that 40-60 per cent of those deaths are due to acute respiratory infection resulting from environmental factors, particularly particle emissions from solid fuel use (Smith, Corvalán and Kjellström 1999). In the United States, a 10 µg/m3 increase in fine particle air pollution results in a 4 per cent increase in general morbidity, a 6 per cent increase in cardio-pulmonary mortality and an 8 per cent increase in lung cancer mortality (Arden-Pope and others 2002).

In the short term, disease due to environmental change is likely to have more impact on developing countries than on developed ones. This is partly because developed countries have devoted considerable effort to reducing the health threat from dirty water, poor sanitation and using solid fuels in open fires inside homes. The same is not true for most developing countries. As a result, exposures to particulates for non-smokers are often an order of magnitude lower in developed countries than in developing ones. In Helsinki, for example, the particulates in the air come mainly from indoor dust, cleaning products, traffic and long-range transport (Koistinen and others 2002). In developing countries, the use of solid fuel as a primary energy supply dominates the exposure of non-smokers to particle pollution, especially among women and children in rural and slum environments. In the past decade, smoke haze from forest fires has also become an important source of respiratory disease (see image above). Furthermore, most developing countries still lack the resources to deal effectively with public health crises and are situated in regions where many water-borne and vector-borne diseases are acute.

Microbiological contamination of the sea by sewage pollution has precipitated a health crisis of massive proportions globally. Bathing in polluted seas is estimated to cause some 250 million cases of gastroenteritis and upper respiratory disease every year, with an estimated annual cost worldwide of about US$1.6 billion. Some of these people will be disabled over the longer-term, suggesting that the global impacts of marine pollution are comparable to those of diphtheria and leprosy (see also Marine pollution). Eating sewage-contaminated shellfish causes an estimated 2.5 million cases of infectious hepatitis a year, of whom some 25 000 die and another 25 000 suffer longterm disability resulting from liver damage. The annual global burden on human health is estimated to equal some 3.2 million DALYs - comparable to the worldwide impact of all upper respiratory infections and intestinal worm diseases - and to cost world society some US$10 billion annually (GESAMP 2001).