Health organizations around the world warn that much of the progress achieved in recent decades improving human health is at risk. Severe economic and social crises, and natural disasters in diverse places have caused many national health systems to collapse, resulting in a resurgence of diseases that were once under control. Conditions are especially critical where there is a proliferation of slums and squatter settlements with millions of people lacking safe and adequate drinking-water, sanitation and solid waste disposal facilities. Insufficient attention is paid to these problems by the global community, allowing the problems to escalate beyond reason, and the suffering to continue unchecked.
According to the OECD (2002), 3 million people die each year due to air pollution and 5 million due to unsafe water.
Statistics from the United Nations Development Programme (UNDP, reported to Rio+5 conference in 1997, are that: about 1.5 billion people live with dangerous air pollution, 1 billion live without clean water, and 2 billion without sanitation. Almost half the world's population suffers from diseases associated with insufficient or contaminated water where they are at risk from waterborne and food borne diseases, of which diarrheal diseases are the most deadly.
Some of the important environmental diseases and hazards are : (a) faecal-oral infections arising from pathogens in polluted water, food, milk, etc; (b) respiratory infections due to crowding and poverty; (c) vector-borne diseases associated with diverse ecological factors and conditions; (d) parasitic infections flourishing under ecological conditions which favour intermediate hosts, and favoured by certain unhygienic conditions and human behaviour; (e) chronic obstructive lung disease through exposure to dust (often occupational or domestic); (f) lead poisoning as as result of occupational, domestic and environmental contamination, particularly from motor vehicle emissions; (g) other heavy metal poisoning from contaminated soil and industrial fallout; (h) cancer and birth defects induced by radiation and organic chemicals, including pesticides and petrochemicals; (i) mental and psychological disorders arising from social stress, such as the breakdown of traditional lifestyles, unemployment and mass migration.
It is estimated that in European cities around 80 000 adult deaths a year are related to long-term exposure to traffic-related air pollution, using the proportion of ambient PM10 concentration due to traffic as an indicator. Both short and long term WHO air quality guideline values are frequently and considerably exceeded in the European Region, in particular for ozone, NO2 and particulate matter.
The World Health Organization estimates that poor environmental quality contributes to 25 per cent of all preventable ill-health in the world today (WHO 1998). Traditional problems, such as contaminated water, poor sanitation, smoky indoor air and exposure to mosquitoes and other animal disease vectors, are still the primary environmental factors in ill health. Across the world, insufficient water supplies, inadequate sanitation and poor hygiene are primarily responsible for global outbreaks of cholera and other diarrhoeal diseases, which claim three million lives each year (WHO 1997a).