Title of Example

Example

Introduction

What follows is a short review on air quality index used in some European cities and in USA.

Air Quality Index in France (ATMO Index)

In France, the ATMO index identifies the typical characteristics of overall air quality for agglomerations larger than 100,000 inhabitants.

This index is determined using levels of pollution measured throughout the course of the day by urban and peri-urban stations for background pollution in the city.

The type of measurement site in question is precisely defined: they are background pollution sites that must be in densely populated areas. Therefore, for sulphur dioxide, the population density must exceed 4,000 inhabitants per km² within a radius of 1 km around the site.

For nitrogen dioxide, ozone and dust particles, the population density must correspond to the same criteria. Moreover, the NO/NO2 ratio for the site must be less than or equal to 1 (typical characteristic of a site situated at some distance from trunk roads).

The ATMO index takes into account the different sources of air pollutants.

The following pollutants are taken into account:

- sulphur dioxide (from industrial plants);

- dust particles (from industrial plants and motor vehicles);

- nitrogen dioxide (mostly from motor vehicles);

- ozone (from motor vehicles).

For each pollutant, a sub-index is calculated. Each sub-index is determined every day using a mean of the levels of the pollutant examined on all of the stations used. For dust particles, the mean daily concentration on the site is taken.

For sulphur dioxide, nitrogen dioxide and ozone, the maximum hourly concentration on each site for the day in question is taken.

The maximum sub-index is selected as the final ATMO index, characterising the overall air quality.

Calculation chart for 4 sub-indices:

Table 1 - Sub-indices calculation.

The ATMO air quality index is in fact a figure between 1 and 10 linked to a qualifier:

Table 2 - ATMO Index calculation.

Each day, the ATMO air quality index is calculated until 4 p.m. and is published as of 5 p.m. The definitive daily index is known the following day from 9:30 a.m. onwards. What is more, every day at 12:30 p.m., an ATMO index forecast is carried out for the same day and the following day, available for consultation on the French Minitel system and the Internet.

Since the end of 1999, air quality can also be consulted on one of the most visited web sites in France: www.tf1.fr in the "Services" page.

The estimated daily index is also announced every evening at the end of the regional news bulletin on the French television channel, France 3, on the teletext service of French television channel France 2, and in different daily newspapers (Le Figaro, Le Parisien, etc.). It is also broadcast by a number of radio stations covering the Paris region (Skyrock, BFM, etc.) and given on the 170 public information boards situated throughout Paris.

See the web site: http://www.airparif.asso.fr/english/indices/atmo.htm

Air Quality Index in Stockholm (Sweden, EMMA Index)

The EMMA index, used by the City of Stockholm (see http://www.slb.mf.stockholm.se/), deals with pollutants separately, because it takes into account their different effects on human health.

Air quality classes are defined on the basis of limit values fixed by European Directives by WHO guidelines and atmospheric pollution local conditions (estimated through statistical analysis of data collected at the local air quality monitoring network).

Terms used to characterise different levels of human and vegetation exposition, refer to the EC Air Quality Directives and to WHO (see the 1987 and 1995 guidelines) terminology:

- ”Limit Value”: limit value that must not be exceeded to prevent dangerous effects on health and/or environment;

- “Target value”: a level fixed with the aim of avoiding more long-term harmful effects on human health and/or the environment as a whole, to be attained where possible over a given period;

- “Guide Value”: recommended value, under which environmental effects are not important.

Quality judgement is based on the following considerations:

- need to protect more sensitive population groups, to warn population if risks for human health are occurring and to avoid vegetation damages;

- air quality targets must guarantee a better quality of atmospheric environment;

- past air quality situation has to be considered adequately.

Concentration levels that separate different quality classes are (see also Table 1):

- Annual Average Concentration (AAC). Air Quality annual conditions are compared with annual standard fixed by legislation. For polluted areas where this standard is exceeded, AAC is put equal to the standard. When standard is not exceeded or in absence of recommendations on annual average conditions, it can be convenient to calculate the annual average registered more frequently in the past and to assign that data to AAC.

- Target Value Concentration (TVC) for acute exposures. This value is generally put in relation with standard limit values and it can be used for short period exposure. When a target value is not available it is better to define it as the more probable daily average concentration.

- Upper Limit Concentration (ULC) and Lower Limit Concentration (LLC). They are based on human health exposure. Obviously lower limit is more easly reachable. Generally ULC is the double the LLC value.

- Intermediate concentration between TVC and AAC is the IVC (Intermediate Value Concentration). This value corresponds to vegetation protection limit value. When it is greater than the limit for health effects, the limit for vegetation corresponds to LLC and the IVC is put in the middle of range between TVC and AAC.

- The last subdivision is between TVV and IVV (AVC). The aim is to characterise conditions when it is necessary to warn population about acute pollution episodes. It is described by the Alert Value Concentration (AVC). If it is not defined by the Authority, it corresponds to the 85% of TVC.

According to the previously defined Concentration levels, the indeces that characterise the air quality state are reported in Table 3. In urban context the evaluation method could be focussed on health risk for population, while in a rural or suburban context it should take into account different effects on plants and animals.

The EMMA air quality index has been applied and validated for Athens city, using monitoring data referred to 1983-1995 (Kassomenos et al., 1996).

The index characterises the daily state of air quality for all measured pollutants.

Table 3. - Index and quality air class respect to limit value (Kassomenos et al., 1996).

See the web site: http://www.slb.mf.stockholm.se/

Air Quality Index in Madrid (Spain)

27 monitoring stations are spread over the city, measuring several pollutants: SO₂, CO, NO, NO_X, NO₂, PM_2.5, PM₁₀, ozone, BTX, etc.

Only 4 pollutants are included in the Air Quality Index: NO₂, CO, SO₂ and ozone. The city is divided into eight sections and the level of pollutant in each sections is catalogued as good (green colour), admissible (yellow), high (orange) or very high (red). Additionally, the daily average value of PM₁₀ is also given:

Figure 1. - Index Air Quality Index in Madrid (Spain).

The index time of updating is 24 h, but you can have the data provided by the monitoring stations hour by hour, depending on the pollutant and the monitoring station considered.

Information to the public and alert thresholds for average daily measurements provided by the monitoring stations are 125 and 200 μg/m³ respectively for SO₂, 125 and 150 μg/m³ for PM₁₀ and 300 (1 hour) and 400 (3 hours) μg/m³ for NO₂.

The information provided to the public consists on the following: 1) Call centre (Phone number: 010), which incorporates a service for environmental information; 2) information points, with tactile displays; 3) website; 4) email to the mass media including news about environment; 5) electronic panels in sport centres, which inform about the levels of some pollutants (low level: green colour, medium: yellow, high: red) such as SO2, PM10, CO, ozone, UV; 6) display screens installed in the streets which inform about some aspects of atmospheric and acoustic pollution.

In the website of the Municipality of Madrid (http://www.mambiente.munimadrid.es/) it is possible to find more information about the Environmental Information System of the city (SIM: Sistema de Información Medioambiental).

Air Quality Index in Helsinki (Finland)

In order to simplify the air quality information distributed to the public, the air quality index invented by YTV (Helsinki Metropolitan Area Council) is being used in the Turku region.

When calculating the index values, the concentrations of pollutants are compared to the Finnish guideline values (see Table 4). In 2002, the index was improved and now it is totally based on hourly averages. On the basis of the concentrations measured, the sub-index values are calculated, each on an hourly basis. Referring to the sub-indices, the highest value is chosen to be the index value of the hour, and the highest hourly index value characterises the daily air quality index.

Table 4 - Calculation of the air quality index.

The index value of 100 equals the guideline value (exception PM₁₀). In the verbal characterisation, health and material-related impact as well as the effects on nature are also taken into account (see Table 5).

Table 5 - Determination of the air quality index as of 2002 (Helsinki Metropolitan Area Council).

The calculation of the index is based on the components monitored in a station, e.g. in one station the components can be NO₂, CO and SO₂, and in another only PM₁₀ and NO₂.

Link to Helsinki Metropolitan Area Council: http://www.ytv.fi/english/air/now.html

Air Quality Index in Malmö (Sweden)

It is based on hour values measured at the City Hall (roof level in the city centre) från Rådhuset (Centrum taknivå), Fosie (roof level in the outskirts) and Rosengård (roof level in the outskirts). Substances used are: sulphur dioxide, nitrogen dioxide, ozone, carbon monoxide and PM₁₀.

The index is the sum of the indeces for each of the substances minus a correction factor. The correction factor is the number 15 which is subtracted from the sum of the individual indeces. The individual indexes are an attempt to characterize the concentrations as low, average, high etc. This characterization is mainly based on limit values and recommendations for the different parameters. The individual index has five levels: very low, low, average, high and very high. There are five substances and consequently five points/numbers having equal weight/strength.

The following scheme has been used:

Table 6

The sum-index has following characterization:

0-15 = very low

15-30 = low

30-60 = average

60-120 = high

<120 = very high

US EPA Air Quality Index (AQI)

The AQI is an air quality indicator developed by the U.S. E.P.A. to provide uniform and easily understandable information about the daily levels of air pollution.

The AQI is reported as a percentage of the federal health standard.

An AQI reading between 101 and 150 is considered unhealthy for sensitive groups such as children, asthmatics and people with existing respiratory ailments, and these groups should limit strenuous outdoor activities under these conditions.

AQI readings greater than 150 are considered generally unhealthy, and it is recommended that even otherwise healthy people should consider limiting strenuous outdoor activities.nbsp;

The following table provides a list of the ranges and colors for the Air Quality Index and the related description of general health effects for each range:

AQI Category Index Values, Descriptors, and Colors:

Table 7

The groups most sensitive to the specific pollutant for any reported index greater than 100 are:

- Ozone: children and people with asthma are the groups most at risk.

- PM_2.5: people with respiratory or heart disease, the elderly and children are the groups most at risk.

- PM₁₀: people with respiratory disease are the group most at risk.

- CO: people with heart disease are the group most at risk.

- SO₂: people with asthma are the group most at risk.

- NO₂: children and people with respiratory disease are the groups most at risk.

The AQI can be calculated by using the pollutant concentration data, the breakpoints in Table 1, and the following equation (linear interpolation):

Where:

I_p = the index for pollutant _p; C_p = the rounded concentration of pollutant _p; BP_Hi = the breakpoint that is greater than or equal to C_p; BP_Lo = the breakpoint that is less than or equal to C_p; I_Hi = the AQI value corresponding to BP_Hi; I_Lo = the AQI value corresponding to BP_Lo

Table 8 – Breakpoints for the AQI.

See the web site: http://www.epa.gov/airnow/

Acknowledgments

City of Stockholm Administration for the information provided on EMMA Index.

Last Updated

13th January 2005