Achievements in air quality management underlie increased economic and social welfare in many developing countries. Sound air quality management is also a proven way of enhancing public health, since air pollution is associated with increases in outpatient visits due to respiratory and cardiovascular diseases, in hospital admissions and in daily mortality. Recent estimates of the increase in daily mortality show that on a global scale 4-8% of premature deaths are due to exposure to particulate matter in the ambient and indoor environment. Moreover, around 20-30% of all respiratory diseases appear to be caused by ambient and indoor air pollution, with emphasis on the latter. It is suggested that without clean air, a sound economic development becomes virtually impossible and social conflicts inevitable.

Although enormous progress has been made in developing clean air implementation plans for urban areas, especially in developed countries, a substantial number of people living in urban areas - around 1.5 billion, or 25 per cent of the global population - are still exposed to enhanced concentrations of gaseous and particle compounds in the air they breathe. And the use of open fires for indoor cooking and heating currently exposes about 2 billion people to quite substantial concentrations of suspended particulate matter, 10-20 times higher than ambient concentrations according to the limited measurements available. Other sources of air pollution include industrial and vehicular emissions, as well as vegetation fires. Furthermore, the rate of population growth continues to increase and is likely to peak around the year 2000, leading to a doubling of the global population by the middle of the 21^st century. Most population growth will occur in low-income countries and will stress already inadequate infrastructures and technical and financial capacities. In parallel, the process of urbanisation will continue, such that the proportion of the global population living in cities will increase from around 45% to around 62% by the year 2025, creating dense centres of anthropogenic emissions.

The primary aim of the WHO Guidelines for Air Quality is to protect public health from the effects of air pollution, and to eliminate or minimize exposure to hazardous pollutants. Air quality guidelines are set up to help governments derive legally enforceable air quality standards, and to guide the environmental health authorities and professionals who are trying to protect people from the harmful effects of environmental air pollution.

Agenda 21 states in Chapter 6 on human health and environmental pollution:

The WHO Guidelines for Air Quality should help to greatly reduce the burden of excess mortality and preventable disability suffered by the poor. It should also help counter potential health threats resulting from economic crises, unhealthy environments and risky behaviour. In this sense, the Guidelines contribute to meeting two of the key challenges that were highlighted in the 1999 World Health Report and, thus, they contribute to making health a fundamental human right.

Dr Richard Helmer
Director, Department of the Protection of the Environment

The risks posed to human health by air pollution have been evaluated since the 1950s and guideline values were derived in 1958. In 1987, the WHO Regional Office for Europe EURO published the Air Quality Guidelines for Europe. Since 1993, these guidelines have been revised and updated. In a recent Expert Task Force Meeting convened in December 1997 in Geneva, Switzerland, the Guidelines for Air Quality was extended to provide global coverage and applicability, and the issues of air quality assessment and control were addressed in more detail. The WHO Guidelines for Air Quality document is the outcome of the consensus deliberations of the WHO Expert Task Force.

The WHO Guidelines for Air Quality provides a basis for protecting public health from the adverse effects of environmental pollutants and for eliminating ,or reducing to a minimum, contaminants that are known or likely hazards to human health and well-being. The Guidelines does so by providing background information and guidance to governments for making risk management decisions, particularly in setting standards. It also helps governments carry out local air quality control measures.

The WHO Guidelines for Air Quality values are levels of air pollution below which lifetime exposure, or exposure for a given averaging time, does not constitute a significant health risk. If these limits are exceeded in the short-term it does not mean that adverse effects automatically occur; however the risk of such effects increases. Although the Guidelines for Air Quality values are health- or environment-based levels, they are not standards per se. Air quality standards are air quality guidelines promulgated by governments, for which additional factors may be considered. For example, the prevailing exposure levels, the natural background contamination, environmental conditions such as temperature, humidity and altitude, and socio-economic factors.

When proceeding from the Guidelines for Air Quality to standards, policy options include such questions as what proportion of the general population, and which susceptible groups, should be protected. Several additional items must also be considered: the legal aspects; a definition of what constitutes adverse effects; a description of the population at risk; the exposure-response relationship; the characterisation of exposure; an assessment of risks and their acceptability; and the financial costs of air pollution controls and their benefits.

The Air Quality Guideline has been prepared as a practical response to the need for action with respect to air pollution at the local level, and for improved legislation, management and guidance at the national and regional levels. WHO will be pleased to see that these Guidelines are used widely. Continuing efforts will be made to improve its content and structure. It would be appreciated if users of the Guidelines would provide feedback and their own experiences. Please send your comments and suggestions on the WHO Guidelines for Air Quality – Guideline document directly to the Department of Protection of the Human Environment, Occupational and Environmental Health, World Health Organization, Geneva, Switzerland (Fax: +41 22-791 4123, e-mail: schwelad@who.int).

Acknowledgements

The WHO thanks all individuals who contributed to the preparation of the Guidelines for Air Quality. The international, multidisciplinary group of contributors and reviewers are listed in the "Participant list" in Annex 5. Special thanks are due to the chairpersons of the meeting and workgroups of the WHO expert task force meeting, held in Geneva, Switzerland in December 1997: Dr Robert Maynard, who acted as the chairperson of the meeting; Professor Morton Lippmann and Professor Bernd Seifert, who chaired the three workgroups. Thanks are also due to Dr Frank Murray for acting as rapporteur of the meeting and reviewing the draft document. Contributions from those who provided the background papers and who contributed to the success of the WHO expert meeting are gratefully acknowledged:

Prof. Dr Ursula Ackermann-Liebrich, University of Basel, Switzerland;
Dr Amrit Aggarwal, National Environmental Engineering Research Institute, Nagpur, India;
Mr Jonathan Bower, AEA Technology, Culham, United Kingdom;
Dr Bingheng Chen, World Health Organization, Geneva, Switzerland;
Dr Mostafa El-Desouky, Ministry of Health, Kuwait
Dr Ruth Etzel, Centres for Disease Control and Prevention, Atlanta, GA, USA;
Dr Hidekazu Fujimaki, National Institute for Environmental Studies, Ibaraki, Japan;
Dr Kersten Gutschmidt, World Health Organization, Geneva, Switzerland;
Dr Richard Helmer, World Health Organization, Geneva, Switzerland;
Dr Michal Krzyzanowski, WHO European Centre for Environment & Health (ECEH), De Bilt, Netherlands;
Dr Rolaf van Leeuwen, WHO European Centre for Environment & Health (ECEH), De Bilt, Netherlands;
Mr Gerhard Leutert, Federal Office of Environment, Forests and Landscape, Bern, Switzerland;
Professor Morton Lippmann, New York University Medical Centre, Tuxedo, NY, USA;
Ms Angela Mathee, Eastern Metropolitan Substructure (Johannesburg), Sandton, South Africa; Dr Robert L. Maynard, Department of Health, London, United Kingdom;
Professor Frank Murray, Murdoch University, Murdoch, Australia;
Professor Mahmood Nasralla, National Research Centre, Dokki, Cairo, Egypt;
Dr Roberto Romano, Pan American Health Organization/WHO Regional Office for the Americas, Washington, DC, USA;
Dr Isabelle Romieu, Centres for Disease Control and Prevention, Atlanta, GA, USA;
Dr Dieter Schwela, World Health Organization, Geneva, Switzerland;
Professor Bernd Seifert, Institute for Water, Soil & Air Hygiene, Federal Environmental Agency, Berlin, Germany;
Dr Bimala Shrestha, WHO Representative's Office, Kathmandu, Nepal;
Professor Kirk Smith,University of California, Berkeley, CA, USA;
Dr Yasmin von Schirnding, World Health Organization, Geneva, Switzerland;
Professor Gerhard Winneke, Univerität Düsserldorf, Germany;
Dr Ruqiu Ye, National Environmental Protection Agency, Beijing, People's Republic of China;
Dr Maged Younes, World Health Organization, Geneva, Switzerland.

Particular thanks are due to the Ministry of Environment, Bonn, Germany; and the Federal Office of Environment, Forests and Landscape, Bern, Switzerland. They provided funding to convene the WHO expert task force meeting in Geneva, Switzerland, in December 1997, to produce the Guidelines.