Chapter 1: Improving Information and Expertise for Air Quality Management

1.1 Preparing Basic Overview Information
1.2 Involving the Stakeholders
1.3 Clarifying Issues
1.4 Prioritizing and Selecting Air Quality Issues

Information is essential for successful Air Quality Management. For an issue specific working group on Air Quality to progress effectively through the Environmental Planning and Management process, a sufficient amount of relevant and reliable information is necessary at each stage. Information must be properly analysed and understood so that technical dimensions of the problems are known and the feasibility of various approaches is appreciated.

Cities have found that information about air quality and related problems is often limited, at least in terms of what is readily available. Useful information and expert knowledge often exists but is not readily accessible. It is typically found in many different forms in many different organizations and groups. These organizations and groups usually do not easily share with one another. In practice, working groups generally find that they do not need to generate much new information. Their real task is to better identify the available information and expertise, bring them together and restructure and reformat the information to make it easily applicable to the needs of the working groups, the Air Quality Management process, and their specific urban situation. Despite the highly technical nature of some of the information, it is generally possible to create a user-friendly form relevant for Air Quality Management activities.

1.1 Preparing Basic Overview Information

The first tangible output of the EPM process in a municipality usually is the development of an Environmental Profile (EP). Key stakeholders from different sectors - private, public, and community - are involved through a consultative process in the preparation of the Environmental Profile and in identifying the environmental priority issues facing the municipal areas. The main objectives of the EP are to clarify the environment-development interactions in an urban setting. A City Consultation follows the preparation of the profile where stakeholders from all levels of government and relevant sectors come together to deliberate and agree on environmental priority issues confronting their local authority. The Environmental Profile focuses on the environment from an urban development point of view. It reviews the use of the city's environmental resources by different users (e.g. resource depletion), and the impact of city activities upon the different environmental resources (e.g. pollution impacts).

The first chapter of the EP (City Introduction) discusses the city's setting. It contains information such as the geography, location and most relevant features of the settlement.

The second chapter (Development Setting) discusses the main activity sectors in the city - such as urban expansion and renewal, mobility, commerce and industry, tourism, culture and leisure - and their relation to the city's environmental resource attributes. This chapter also describes the degradation of the city's air quality caused by urban development activities.

The third chapter (Environmental Setting) discusses the environmental resources (including air) in the city. This section on air includes the air quality situation citywide resulting from the impacts of the different activity sectors (as discussed in the second chapter). This chapter also brings together available information on the environmental situation, sources of pollution, and recent trends.

The final chapter (Institutional Setting) reviews the important stakeholders who play a role in urban development and environmental issues. Emphasis is on the city's main environmental management mechanisms, particularly those that are focused on the city's natural resources.

The Environmental Profile is presented and discussed in a City Consultation. The City Consultation brings together the work of Phase One of the Environmental Profile Management process. The City Consultation provides a mechanism for a meaningful and more active participation of the various city stakeholders through collective identification of the problems and coming to a consensus on the priority of urban environmental issues. It consolidates support and commitment from the different stakeholders.

From Environmental Profile to an Air Quality Profile

Experience with City Consultations has shown that air quality is a priority issue for many municipalities, cities, and agglomerations in developing countries. The EP provides an important information base because it serves as a common context for all groups working on air quality and other environmental issues. By design though, the Environmental Profile is not meant to contain very detailed information on any one resource (such as air). Working groups have generally found that more detailed information is necessary, because the issues must be further clarified before considering options and formulating strategies. Consensus is usually reached on the need to prepare an Air Quality Profile (AQP).

Since the Environmental Profile (EP) covers all the city's important environmental issues, the Air Quality Profile will contain valuable information on air quality and the factors affecting it (such as activities with negative effects, conflicts of interest over air pollution, overview of the organizations and groups involved in air quality management). The EP provides the first basic source of information for any air quality working group (or other groups grappling with air quality management issues). The first task of any working group preparing an Air Quality Profile should be to thoroughly review the EP in order to extract the wealth of available information and to identify gaps where progress needs to be made.

Developing country cities have found the following useful ways of improving the air quality information base:

• Preparing an Air Quality Profile
• Detailed mapping of the city's air quality situation / problems
• Holding a city-wide consultation on air quality issues (a mini-consultation)

a) City Air Quality Profile (AQP)

The Air Quality Profile (AQP) is a document similar to the general Environmental Profile (EP) but is focused exclusively on air quality. It follows the same structure and logic as the EP. The Air Quality Profile's objective is to discuss, in detail, the present air quality situation in the city, to examine how and which activity sectors are causing which kinds of air pollution, to identify those affected by air pollution, to show what the specific problem areas are, to highlight conflicting interests, and to assess the existing policies and institutions active in addressing the issues. One of the first activities of the working group should be the production of an AQP. The AQP should be developed as a working document that is continuously updated with new information and insights as soon as they become available.

TOOL 2, City Air Profile, explains the importance of an air profile of the city and gives stepwise guidelines for working groups on how to prepare a city Air Quality Profile.
One of the most important tasks at this time is to provide detailed information about various types of air pollution. Different types of pollutants (NOx, SO2, Ozone, particulate matter of critically different sizes, organic compounds, etc.) have very different characteristics, causes, and effects.

TOOL 4, Overview of Air Pollutants, provides a systematic overview on the different classes and types of air pollutants, their typical sources, their characteristics, their health effects and other effects, their technical terminology, etc.

TOOL 1, Factors Influencing Urban Air Quality, explains that the level of air pollutants is greatly influenced by the area's prevailing geographical, climatological and meteorological conditions, as well as by city planning and design. TOOL 1 gives a general overview of these factors influencing a city's air quality and illustrates how these factors can be identified and assessed.

b) Mapping

Monitoring data on air pollution (by type), location of specific air quality problems and main polluting sources, concentration of respiratory diseases, distribution of citizens complaints, etc are all relevant information that can be plotted in maps. Putting the information into maps is a helpful analytical device that clearly shows spatial relationships between pollutants and human activities. Detailed maps should be an integral part of an Air Quality Profile.

TOOL 5, Mapping Air Quality Issues, gives an outline of air quality mapping procedures as essential tools for presenting a city's air situation, improving decision-making, and prioritizing air quality issues. The tool also includes actual examples from some SCP demonstration cities. In addition, the SCP Source Book on Environmental Management Information Systems (EMIS) gives valuable, more detailed information on a step by step mapping approach based on Geographic Information Systems (GIS).

c) Consultative meetings on air quality

As the air quality working groups discuss the topic of air quality in greater detail, they begin to see the need for participation of a larger group of members. Increased participation can be accomplished through specially organized workshops, often called mini consultations. These are organized similar to the more comprehensive City Consultations but with a specific focus on the issue of air quality. Broad stakeholder involvement in these consultations remains very important.

Cities have found mini-consultations useful for:

• Creating and exploring new information or insights which had not yet been included in the city air quality profile;
• Providing an opportunity for stakeholders representing different interests to give their opinions about the information collected for the Air Quality Profile;
• Giving a much clearer idea of what are perceived as the most urgent air quality problems, for whom, and why, through broad-based participation;
• Supplying a variety of useful inputs which can be used to update and revise the Air Quality Profile;
• Discussing strategy ideas and proposals in order to obtain initial reactions and to elicit more ideas and options;
• Forming further working groups on specific sub-issues related to air quality due to the wide variety of stakeholders present.

1.2 Involving the Stakeholders

Cities all over the world have found that involvement of a broad range of city stakeholders is essential for successful air quality management. Wide-ranging participation by all interested groups and organisations is vital for any type of urban environmental or development management process. Stakeholders must be involved at all stages of the process including: information collection and analysis, prioritization of issues, review and assessment of strategies, formulation of strategies, action planning, and most importantly implementation of investment projects and institutionalising the entire process. Cities have been successful in addressing air quality problems by bringing in a wide range of relevant stakeholders. These stakeholders include:

• Those who possess expertise in air quality management and/or have important information about different aspects of the issue;
• Those whose interests are directly affected by urban air quality management issues;
• Those who control or influence important instruments or mechanisms of management;
• Those whose actions directly impact on the air quality situation.

One of the early tasks in a SCP project is to systematically identify the stakeholders who are relevant for the various priority issues. Volume 1, Chapter 2.1.2 of the EPM Source Book on Implementing the Urban Environment Agenda and Volume 3 of the SCP Source Book series on Establishing and Supporting a working group process provide valuable insights on how to effectively identify the relevant stakeholders.
One may identify stakeholders by starting with the knowledge possessed by the core participants in the project. Additional stakeholders can be progressively identified through the preparation of the Environmental Profile and through the preparations for and holding of the City Consultation. There is a major effort involved in the early stages to find and mobilize stakeholder participation. As the work proceeds, the range of participating stakeholders is continually refined and supplemented.

One important reason to involve a wide variety of stakeholders is to facilitate the assembly of relevant information. For example, universities, various governmental research departments and institutes, industries, and other organizations often have and/or collect air quality data on the city. However, this information often is incompatible and recorded or kept in different formats because the information was collected for different purposes. Other information relevant to air quality (e.g. motor vehicles and traffic information) is available from other organizations. Quite commonly, the separate organizations have little idea of what data is gathered or accumulated by the other. There is generally very little communication and almost no exchange or sharing. Some data will often overlap while other, important data is missing. Thus, cities often find that information needed for air quality management activities is not readily available.

Working together on an agreed set of issues and problems can foster a willingness to share data and information, as many working groups in SCP demonstration cities have discovered. A related function that the working group can fulfill if its membership is sufficiently inclusive of key stakeholders, is to help integrate the different and perhaps incompatible sets of data and information. This process, while difficult and time-consuming, can help create a reasonable information base without the considerable expense attendant to new primary data gathering. Also, a broad-based working group membership can help identify the gaps in the various data sets so that measures can be taken to find missing information.

1.3 Clarifying Issues

Conflicts of interest between stakeholders over air quality issues do happen. In order to formulate guided strategies and action plans, it is imperative that air quality issues and their relation to development activities be carefully analysed and clarified. These clarifications can be achieved by applying all available technical means and by broad stakeholder involvement.

1.3.1 Involving Stakeholders in Clarification
Air quality issues can be clarified with as much detail as possible through many means including the preparation of an Air Quality Profile and mapping exercises for air quality purposes in the city. Depending on the level of information obtained from these various means, working groups with representatives from a broad range of stakeholders can be constituted.

The task of the working group is to further clarify the issues that require more definition and analysis. When clarifying issues, working groups should first focus on:

• Identifying and collecting the existing data on the issue of priority;
• Converting and presenting this data in a format that is useful for the working group;
• Identifying missing information on the issue of priority;
• Identifying the appropriate sources of missing information, i.e. who is likely to possess this information;
• Developing strategies for obtaining the information as well as linking up with these potential information sources.

Information can be available from various government departments, research institutes, universities, private sector organizations, and popular sectors working in air quality or general environment and development related fields. A deliberate attempt should be made to include these informative stakeholders in the working group.

The work of this group may entail field visits to and surveys of, for example, mobile stations to witness and experience the level of pollution and to register complaints by various affected persons. One of the main responsibilities of the working groups is to collect the scientific and technical data available about the city's air quality situation and problems, and translate this data into usable information for the use of the working group and for the city stakeholders. Many cities have monitoring equipment and systems for specific air pollutants. Many cities know how much traffic of which types is going through which areas. Many cities have data on the type and amounts of emissions by industries, etc. Often, this data is collected and stored in institutes and technical reports that do not reach the desks of decision-makers, let alone other stakeholders. Even if the information does reach the stakeholder, it may not be in a readily usable format. Working groups should make the effort to determine what exactly is available in the city, which organizations are involved, and which organizations should be a part of the working group.

It is important to be able to identify the right sources for information needed to further clarify an issue. It is equally important that this exercise produces all relevant information necessary for the working group to be able to follow the EPM process and come up with strategies and action plans.

The involvement of technical experts helps clarify and prioritize issues. Their technical expertise and experience bring credibility to the process. They not only enrich the information available but also are instrumental in facilitating the process of consensus building. However, the role of experts is subordinate to that of the stakeholders. Even with the best experts around, not much can be done without the support of the stakeholders.

1.3.2 Emissions Assessment for Clarifying Issues
Emissions assessment techniques are an indispensable part of air quality management. With technical experts available, emissions assessments should be undertaken because they help identify the main sources of pollution in the city and assess the interconnectivity between the various sources of pollution.

Emissions assessment also helps to identify the underlying reasons for the polluting activity sectors. Emissions assessment illustrates, for example, that factories equipped with (often simple) pollution control measures emit less than uncontrolled factories.

There are many ways to further clarify air quality issues. The following methods are discussed below:

a) Monitoring the pollution
b) Calculating/ estimating air pollution
c) Use of mapping
d) Emissions inventories

a) Measuring the pollution by monitoring

Monitoring air quality provides the necessary baseline information to identify which pollutants are of major concern and are principal sources of pollution. Continuous monitoring is necessary to clarify air quality issues in greater depth and certainty. The reliability of the monitoring is critical. The methodology used for monitoring must be sound. Actual monitoring must be well documented. Both low-tech and high-tech methods of monitoring are readily available and each one has its advantages and disadvantages. Whichever technology is chosen must be appropriate in terms of the technical capability of the users and the availability of the resources to operate and maintain the technology.

In order to develop a focused monitoring programme meant to further clarify issues (and later to assess improvements due to strategies adopted and implemented), there should be an initial assessment of the pollutants when you select and prioritize air quality issues within the city. Some primary data (such as number of cars within the city, SO2 or SPM levels, emission inventories) that may have been prepared is often available but scattered. This initial assessment will prevent problems (i.e. monitoring pollutants that are not problematic within the city itself). The experience of many cities, long-term commitment, long-term funding, and training are key factors of a successful monitoring programme.

There are basically four ways to measure urban air quality:
1) passive samplers
2) active samplers,
3) continuous analysers, and
4) remote sensors.

Many cities measure the quality of the city's air through monitoring stations. These stations measure the concentration of pollutants in the air, usually including SO2, NOx, PM10 or SPM, VOCs, etc. The measurements of these air pollutants can be done continuously or on a regular (e.g. weekly) basis. The different sampling stations can either work independently or can have direct connections to a central station. This information can be displayed in a time series, showing the change in concentration of the pollutant over time.

In addition to fixed monitoring stations, some cities have mobile stations. These are fully equipped vehicles that can either assess the air quality at any place, or take samples to be analysed later. These mobile stations are often used to investigate complaints and measure the compliance of industries with existing regulations. Information obtained from these stations is particularly useful as a close correlation between source and effects of the pollutants can be established. The combination of information available from the monitoring stations and those from the mobile units can be better presented through preparation of air quality contour maps.

TOOL 12, Measuring City Air Quality, discusses the objectives of monitoring a city's air quality as well as various techniques for measuring the same. These include instrumental methods for monitoring, their advantages, disadvantages and costs, and a summary of the monitoring methods for specific pollutants.

b) Calculating / estimating the air pollution

Measuring air pollution can be very expensive. Not all cities have extensive monitoring networks and/or mobile monitoring equipment. Models and calculations are increasingly being used in the case that this kind of equipment is scarce or the capacities to appropriately analyse samples is weak. Computer models are a relatively fast and inexpensive way of providing air quality information. Because models can be used to evaluate air quality management options, they are also suitable for planning and strategy development.

For example, the average background concentration within a municipal area caused by vehicle exhaust can be calculated if parameters, such as the number of cars, the average mileage driven within a day and the volume of exhaust produced are known.

The Car International Model can assess pollution levels of certain streets (refer to TOOL 13).

The cost-effectiveness of policy measures can be assessed in advance and/or monitored during implementation. If, for example, the emissions of different types of vehicles are known, the achieved emission reduction (when a certain reduction of vehicles has been realized) can be better assessed. Emission calculations make clear what the most serious polluting activities are. This allows for intervention and setting up cost-effective strategies and action plans. It is therefore strongly recommended that emission assessments, like air quality monitoring, be carried out on a regular basis. Emission assessment activities should be institutionalized and should include the exchange of relevant results with the decision-making actors/institutions.

Predicting air quality from multiple sources by using modeling is very complicated. Large-scale models that can handle multiple sources and different pollutants are used only by very specialized organizations. Air Quality Models are best used for isolated sources or situations. For example, Air Quality Models may be used on air pollution caused by traffic (one specific source) in a certain street (one specific place). Air Quality Models may also be used for predicting the air pollution caused by an industry stack, based on wind conditions, how the plume of the stack goes, where the pollutants will be found, and in what concentration.

Advantages of calculating concentrations with dispersion models:

• It reduced the need for complex (and expensive) ambient air monitoring. However, monitoring remains important to calibrate the dispersion models.
• Models can be used to assess the cost-effectiveness of policy measures in advance. By varying the input data one can assess beforehand the expected air quality improvement of response options. For example, the "CAR International" model (TOOL 13) models various options of interventions (such as re-routing of certain types of vehicles) and can calculate the concentration of pollutants respectively.
• To check future air pollution caused by new factories as part of an environmental impact assessment, it is recommended that dispersion modeling be carried out early in the project preparation, before the plant location and detailed design have been finalized.

TOOL 13, Calculating Air Pollution Near Roads Using CAR-International Model, gives information about Car International, a computer model, developed by RIVM, the Dutch National Institute for Public Health and Environment. Car International was a useful model for calculating concentrations of air pollutants near roads. It is currently maintained as the general CAR model. An example of its use in Dar es Salaam is given in the tool.

To complement such a tool, the World Health Organization has published two volumes: 'One Week Training Workshop in Assessment of Sources of Air, Water and Land Pollution and A Tutor's Guide on Rapid Inventory Assessment Technique (RIAS).'

c) Using mapping for clarification

As discussed earlier, mapping is also a very useful tool to display information and clarify issues. Thematic maps will be useful in analysing the extent of the pollution problem from each activity sector (Refer to TOOL 5).

d) Inventory of emissions

TOOL 19, Preparing an Emission Inventory, is a compilation of all air polluting activities in an area. It has two main components:
1) the pollutants (e.g. Nox, SO2) and
2) the sources (e.g. industry, traffic, and domestic).

It specifies the location of each source (point source or mobile source) and the time variations in the emissions. Emission inventories can be of great assistance in clarifying air quality issues because they, among other things, assist in the evaluation of emission trends, which in turn assist in formulating air quality management policies. The construction of a complete, high quality emissions inventory is, however, time consuming and complex.

1.3.3 Clarifying City/Area - Wide Urban Air Quality Problems vs. 'Hot Spot' Urban Air Quality Problems

Further clarification of the city's air quality issues may require an analysis of the problems at different levels within the city. On the one hand, a clear understanding of issues resulting from individual industries or traffic sections, and how they impact their vicinity, may be required. On the other hand, clarification may be needed on the overall impact in the city by the various activities.

a) City/area-wide urban air quality problems

Transport
Transport is a main contributor to high concentration of pollutants in the atmosphere. In many cities, traffic, sometimes in combination with industrial air pollution, is responsible for smog. Cities are increasingly experiencing these problems. On hot summer days, the ozone level may exceed the norm and warnings are given. Emergency measures may be taken such as car bans on particular days. People with cancer and asthma, the elderly, and children may have to stay indoors during such times.

With regard to the transport problem, the World Health Organization has developed a very useful and easy guide, 'One Week Training Workshop on Motor Vehicle Air Pollution' , to execute RIAS based emission assessments. TOOL 8, a spreadsheet model based on the WHO guide that can be used to execute transport emission assessments in cities. This tool has been demonstrated and further adapted to the characteristics of local vehicle emission factors of cities in developing countries, such as Chennai, India. This was a necessary exercise because the emission factors used in the WHO workshop are roughly based on European vehicles and do not take into account vehicles like auto rickshaws.

Industry
In the case of industries, emission factors of different production processes and pollution control measures are included in TOOL 17, which describes a software database called the 'Decision Support System for Industrial Pollution Control (DSS/IPC)'. This tool was developed by the World Bank and offers more possibilities than emission assessments only (see paragraph b below). This tool is a software-based decision support system that assists working groups to calculate air pollution near industrial activities. The model has high potential as an effective air quality management tool for industrial policy.

b) Clarifying site-specific urban air quality problems (Hot Spots)

Transport
Air pollution in specific streets depends on the volume of traffic and on street construction factors, i.e., distance to houses, height of houses, and trees among others. Pollution can be calculated and, if possible, verified with random measurements and included in a city map.

The CAR model as described in TOOL 13 is a screening model for the computation of traffic-induced air pollutant concentrations in cities. The model computes the concentrations of NO2, benzene, and CO at predetermined points in the street. The input data are street geometry, information about the traffic (mean daily traffic and composition), and the background concentrations for specified pollutants.

Another appropriate model is TOOL 14, IMMIS Luft, which runs on the same principles as the CAR model. However, IMMIS LUFT also includes the air pollutants HC, soot, and CO2 . It is useful in calculating the annual average concentrations of benzene , carbon, and the 98_percentile value of nitrogen. The model is used in many German cities. The advantage of this model is that it can be used in combination with GIS (Geographic Information Systems) for mapping. It can also be used with the transport planning system VISUM in order to estimate the effectiveness of transportation planning on air pollution. This tool provides further information on other models for calculating air pollutants such as the CALINE model. More models are mentioned in this tool.

Comprehensive information on the use and advantages/disadvantages of different traffic models is given in the ISIS Air Guide (Chapter 4: Air Pollution Models for Road Traffic).

Industry
Tools for calculating concentrations near polluting activities are based on dispersion models. A dispersion model is a software programme that calculates the concentration of a specific pollutant by using the emissions from the various activity sectors. Dispersion models may give the same results as ambient air monitoring in the cities. Both may give the concentration of a specific pollutant in g/m³ air. The dispersion models are especially useful to analyse air pollution near industries.

TOOL 16, Calculating Air Pollution near Industrial Activities, is a simple tool used to calculate air pollution near single industrial activities. The method, which has been developed by the Dutch National Institute for Public Health and Environment (RIVM) uses a table to calculate the maximum concentration caused by emissions coming from an industrial chimney with a certain height. This tool also shows in which distance from the chimney the highest concentration will be found (in general, the higher the chimney, the farther the distance).

The Sustainable Dar es Salaam Project developed a spreadsheet with all the industrial emissions in Dar es Salaam, Tanzania. Subsequently, the concentrations in the neighbourhood of the chimneys had been calculated based on the correlation factors of TOOL 16. This directly illustrates which industrial emissions result in concentrations that exceed air quality guidelines. As it highlights those industries that can be the main source of local air pollution, the spreadsheet is a tool to set priorities.

If cities are interested in more advanced software dispersion models to assess air pollution near single industrial chimneys, they can get relevant information on how to order and use the software from the 'Pollution Prevention and Abatement Handbook toward Cleaner Production' by the World Bank, (refer also to TOOL 29).

In-Door Pollution
Compared to outdoor sources (such as factories, power plants, heating and vehicles), in-door air pollution is not a large contributor to overall emissions. Nevertheless, a person's health can be seriously affected by exposure to intense indoor air pollution. Inappropriate burning of fuels, bad ventilation conditions, as well as long exposure times are responsible for illnesses, such as respiratory diseases. In traditional societies, particularly women, who spend most of their time in house, are affected by in-door pollution.

Much research has been done on the in-door air pollution emanating from burning fuels. For example, there is an indoor air pollution database for China. The database itself is included in TOOL 18 and is part of the WHO CD-ROM 'Healthy Cities Air Management' .

TOOL 18, Assessing In-Door Pollution, is useful in assessing the in-door air pollution in urban areas. It is based on data prepared for China that takes into account pollutants (e.g. SO2, CO , NOx and BaP ), fuel type (e.g. coal, gas, and biomass), ventilation conditions, cooking/heating equipment, and location (i.e. urban and rural). The adverse effects on human health can be pinpointed by comparing the results of the assessment with the air quality guidelines (see TOOL 6), and improvement of in-door air quality can again be assessed after having implemented response options (such as cleaner fuels or better ventilation).

1.4 Prioritizing and Selecting Air Quality Issues

Almost always, the experience in the SCP demonstration cities has been that air quality issues were not well defined at the onset. People may think that they 'know the issues' but in fact only have a broad outline of the issues. In general, there is a considerable degree of uncertainty as to what exactly is meant by a particular issue: what is really the problem, for whom, why, and in what way? A broad topic like 'air quality' may be comprised of a wide range of sub-issues. Air pollution may mean many different things. More often than not, it is necessary to spend considerable effort to identify and prioritize the particular sub-issues that will become the focus for the air quality working group.

After having met a couple of times, some working groups found that the main issues were straightforward (like pollution from a certain industrial area, from traffic in the city center, or from small-scale industries in specific locations). In these cases, the working groups could select well-defined sub-issues and take them as priorities for further work. The working groups may decide to set up a series of sub-working groups, each focused on one of the priority sub-issues.

Cities have used a variety of methods to identify and prioritize issues. The criteria listed in the EPM Sourcebook have proven useful in many cities. These are systematic criteria helping cities to - more confidently and more transparently - make decisions about which priority issues or sub-issues to work on first. These criteria include:

a) The magnitude of the health impacts associated with the problem
b) The size of urban productivity loss caused by the problem
c) The relative impact of the problem on the urban poor
d) Whether or not the problem leads to an irreversible effect
e) Whether special circumstances offer special opportunities
f) The degree of social/political consensus on the nature or severity of the problem
g) Whether the problem is city-wide or specific to a "Hot Spot"

The relevance of some of these criteria for prioritization of air quality issues and sub-issues is discussed below:

a) The magnitude of health impacts associated with the problem

The health effects of air pollution have always been one of the major reasons for focusing on air quality management. To better understand how different air pollution problems affect health, a number of approaches can be taken.

WHO guidelines on air quality are a very useful reference - especially for countries with no national guidelines. WHO guidelines are widely accepted and scientifically sound indicators of the levels of pollution exposure. The potentially harmful effects of exceeding these standards are also given in these guidelines.

TOOL 6, Air Quality Guidelines, summarizes the WHO air quality standards and guidelines, as well as those from selected countries. This tool is very useful for air quality working groups because it allows them to clearly and objectively show how different pollutants may be affecting health and in what ways the situation exceeds internationally recognized norms.

The health effects of air pollution are highly variable. Different pollutants have different types of health impacts. Health impacts vary by concentration and by type of exposure. Air pollution encompasses a range of different types of contaminants. It is extremely important to understand these different effects. While detailed knowledge is not necessary at this stage of work, a broad idea of the health effects of air pollution is extremely important.

TOOL 7, Health and Other Effects of Common Air Pollutants, gives a detailed overview of the health effects, both acute and chronic, resulting from exposure to certain air pollutants. It combines information drawn from a variety of sources and gives a very useful introduction to the relationships between air pollution and different types of health problems. With the help of this tool, the working group is able to understand the dangers of exceeding the standards provided in TOOL 5.

To further assist in analysing pollution and health effects, an additional series of tools has been assembled. Each of these is laid out as a simple spreadsheet, and each deals with a different pollutant.

TOOL 8, Estimating Health Effects of PM10, is based on research data from the WHO and the World Bank and discusses the health effects of very small solid particles known as PM10 (particulate matter - dust particles of 10 micrometers or less in size). It is these smaller particles - mainly originating from diesel powered vehicles - which have the most serious health impacts. The spreadsheet of TOOL 8 gives a rough estimate of the health effects of different concentrations of PM10 in a city, and shows the correlation between the level of PM10 and disease/ mortality rates.

TOOL 9, Estimating Health Effects of Air-Borne Lead Pollution, is similar to TOOL 8. It is organized in a spreadsheet and relates levels of lead in the atmosphere to potential health effects. TOOL 9 can be used to better understand the health implications of citywide and area-specific concentrations of lead. It gives the potential health benefits of reducing levels of lead to conform to generally accepted standards.

If efforts to reduce lead levels in the city are achieved, the percentage of the population adversely affected will be significantly reduced. TOOL 9 can help predict the improvements.

TOOL 10, Estimating Health Effects of Sulfur Dioxide, is a spreadsheet for calculating the health effects caused by high levels of sulfur dioxide (SO2). It facilitates the analysis of health benefits when sulfur dioxide levels are reduced.

With TOOL 11, Estimating Health Effects of Ozone, issue specific working groups are able to analyse the health effects of high ozone (O3) concentrations and to assess the health benefits of reducing ozone levels in the city. Both of these tools (10 and 11) contain examples, using data drawn from actual experience in SCP cities.

TOOLS 7, 8, 9, 10 and 11 incorporate well-accepted general relationships based on substantial research. Although each city is different in terms of its pollution patterns and in terms of its disease and mortality characteristics, these relationships give a generally reliable picture. For additional methodological support in this subject, more references are provided in TOOL 29.

b) The amount of urban productivity loss created by the problem

In general, translating environmental pollution into economic degradation is more difficult than assessing health impacts. Although the science of environmental economics has developed ways of assessing economic damage resulting from environmental degradation and depletion, this methodology remains somewhat difficult for non-experts. However, TOOLS 7 and 8 can be used to give an indication of how many working days are lost due to health problems caused specific air pollutants. This is particularly useful with respect to dust (in this case meaning all suspended particulate matter of whatever size) because illnesses resulting in lost days of work are one of the greatest impacts of high levels of total suspended particulates (TSP). It must be remembered that the models in TOOLS 7 and 8 are based on background concentrations and specific local areas within the city (e.g. downwind from industrial areas) could well have different values.

By multiplying the number of estimated days of work lost by the average earnings per day, one could get a very rough idea of the loss of money due to the total number of restricted activity days of adults. This is only a rough estimation because other economic impacts can also be quite important. In the long run, for example, days lost to education through sickness in children will have a negative effect on economic growth. Other economic losses could include reduction in a city's tourism industry with visible air pollution acting as a powerful deterrent to tourists, and damage to historic and cultural landmarks by air pollution causing additional costs of repairs and maintenance.

Persistence of high levels of air pollution can also have an important disincentive effect on economic development. The general impression of a city is one important factor influencing investment. In general, cleaner cities attract more external (especially international) investment. Some industries will not consider locations in areas of high air pollution because of production requirements. For example, high-technology electronics manufacturing is sensitive to atmospheric conditions. The protection of production processes against heavy air pollution can be prohibitively expensive.

c) Relative impact of the problem on the urban poor

Urban air pollution has a relatively higher impact on the urban poor than on the general population for several reasons:

• The health of the poor is often below average, reducing their resistance to disease and increasing the chances that they will suffer health effects from air pollution;
• The housing of the poor is usually low in quality, badly ventilated, heated by basic systems using fuels and techniques that produce high levels of indoor pollution (in some urban poor areas, indoor air pollution is the most serious health threat);
• The urban poor often live in less attractive areas near air pollution sources in heavily exposed down-wind areas. This typically exposes them to high concentrations of air pollution that are much more severe than the average city levels.

The Environmental Profile usually includes information about where the poor live and where the lower-quality settlements are situated in the city. This information combined with the more detailed information in the Air Quality Profile should provide a reasonable picture of how and where the poor are affected by urban air pollution.

d) Whether or not the outcome leads to an irreversible effect

When assessing air pollution effects it is important to distinguish between reversible and irreversible outcomes. The air in most cities is replaced within a matter of days; if motor vehicles and industries stopped producing polluting emissions, the quality of the ambient air would improve dramatically and swiftly. In contrast, the contamination of soils or ground water tables can often be reversed only very slowly, if at all.

There may be many irreversible impacts even if the levels of air pollution drop dramatically. The corrosion of buildings is one such example. If a building is exposed to serious air pollution for long enough, the stonework or structure may be damaged to a point beyond repair. Acid rain, a precursor of acid forming pollutants present in the atmosphere, also has grave effects on historical and cultural heritage. Acid rain caused by SO2 and NOx pollution in the city dissolves soft stone, like limestone. This can cause damage to old buildings, statues, and other exposed materials. Besides being a continuous threat to forests, lakes and soils, in many old European cities (such as Athens, Rome, Prague or Moscow) acid rain is a real threat to old buildings, monuments, and statues.

e) Whether special circumstances offer special opportunities

Special circumstances in a city may provide very rare opportunities for addressing air quality situations even if air quality had not been a priority before. In certain cases, air pollution may be addressed because of its strong relationship to other problems being addressed by city management. For example, if the city managers were attempting to reduce traffic congestion within the city centre, the application of public transport and traffic strategies (see TOOL 20) goes hand-in-hand with air quality management in the city centre.

Another example is spatial planning. Spatial planning measures undertaken by city planners could improve the air quality situation of the city. Planning undertaken to mark zones for the operation and expansion of industrial and business activities, away from residential places, helps improve the air quality of the city and reduces the exposure of the city's population to hazardous pollutants.

Special events of a regional or global nature can act as a catalyst to promote local action on air pollution. For example, the global concern about the effects of climate change (a long-term effect of air pollution that causes global warming) culminated in the United Nations' Framework Convention on Climate Change (UNFCC) and in the United Nations' Kyoto Protocol (a framework under which governments take responsibility to mitigate and adapt to the effects of climate change). In order to meet obligations under the convention, governments first sign and ratify the convention and then act locally. Many of these actions directly address air pollution issues.

Air pollution episodes, accidents and disasters also create change. These accidents turn the spotlight on air pollution problems and thus offer a valuable opportunity for including air pollution as a priority. They ignite radical air quality management strategies.

Some examples include:

• Explosions of factories, or gas leakages such as the one that occurred in a Union Carbide factory in Bhopal, India, shocked the whole world. In this accident, the leakage of the highly toxic gas methyl isocyanate (MIC) killed thousands in 1984. Though it reached an out-of-court settlement with the Indian government, Union Carbide refused to accept responsibility for the disaster, blaming it on terrorism and industrial sabotage. However, strong public pressure forced Union Carbide as well as other large chemical companies to implement stricter safety and environmental standards.
• The release of highly toxic dioxin from a small chemical plant in Seveso, Italy, in 1976, led to harsh industrial regulations issued by the European Union.
• The oil crisis in 1974 caused a new perception regarding the use of fossil fuels. Many countries in Europe introduced a so-called 'car free Sunday' that prohibited normal car users from using their cars on Sundays. This policy measure, while introduced to curb fuel consumption, had a positive effect on air quality and focused attention to this issue. Today, Access is closely involved in actively promoting the European Mobility Week - including the Car-Free Day on 22 September each year (http://www.eurocities.org).
• Excessive congestions and high concentration of air pollutants in the city centre of London caused the introduction of a radical 'congestion charge'. This resulted in a drastic change in modal share towards public transport. Other cities introduced different measures to restrict access of private cars to the centres.

f) The degree of social/political consensus on the nature or severity of the problem

Many times, identified air pollution problems need to be accompanied by sufficient scientific data for further clarification. However, in certain cases, the effects and presence of air pollution are very obvious and there is common concern and consensus for action. In such situations, the priority is to act immediately and to not delay urgently required counter strategies, especially if the delay is due to lack of scientific data. At this point, the degree to which the pollutant(s) exceed the laid-down national standards or WHO standards may not be relevant. Complaints arising due to health problems and other complications should be sufficient to trigger response from city managers and decision-makers. The citizens' health problems and complaints should be enough to make the city act. This is particularly true as air quality problems can become manifest in different ways. Air quality problems may be very local and particular to a spot in the city and impossible to measure. In such a situation, the average emission levels in the city may be below standards, but because of local conditions (e.g. strong winds always transporting air pollution towards one direction or the existence of inversion layers) citizens might experience severe problems. The stakeholders, i.e. those affected, should be allowed to be part of the problem definition and solution search.

Political and social consensus on a problem is very important. It is important that all stakeholders are involved in the process of preparation and decision-making to make sure the city and those responsible address all air quality problems. Air pollution also has social costs. Citizens want to live in a city with clean air. Studies based on willingness to pay for clean air suggest that the social costs of air pollution in cities even exceed the cost for direct damage to health and property (Internalising the Social Costs of Transport, OECD, 1988 ).

g) Whether the problem is city-wide or specific to a "Hot Spot"

Distinguish between city-wide or area-specific (hot spots) air pollution. Examples of city-wide air quality problems include smog caused by traffic in large areas of the city and city-wide background air pollution concentrations caused by large industrial areas in or adjacent to the city. Climatological conditions like inversion layers, wind directions, and geographical conditions in a city can affect the concentration of pollution and the magnitude of its impact. For example, hills surrounding a city exacerbate the air quality situation. On the other hand, other natural conditions specific to a city can help reduce air quality problems. The air above a city is able to refresh itself within one-half to three days depending upon the wind, altitude, and absence of geographical barriers (such as mountains and hills).

Hot Spots are specific problems in specific locations. They may include an industry polluting its direct vicinity, pollution of the city centre, and small-scale industrial activities taking place in urban areas. These medium-scale problems are often not affected that much by weather and geographical setting. A main issue in this category is the risk of air pollution caused by industrial accidents.

These issues can be prioritized by working groups formed for specific problems in certain areas/Hot Spots within the city and for city-wide air quality problems.