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Breathable cities

Eleven teams of researchers from ten different countries have studied the relationship between pollution - mainly caused by traffic - respiratory disease and mortality. This European approach has made it possible to study various different sites both as regards pollutants emitted and socioeconomic or environmental conditions.
Do current levels of air pollution affect mortality and morbidity among people living in large towns and cities? The question is answered in the affirmative by the epidemiologists of the APHEA project who have correlated pollution, respiratory disease and mortality in 15 European cities. On the basis of their findings, EU and international standards for tolerable levels of pollutant emission have been revised.


In the 1950s, air pollution caused by industry, mainly suspended particles and mostly sulphur dioxide (SO2), was clearly identified as being responsible for increases in respiratory and cardiovascular mortality. Since then the industrialised countries have adopted a series of basic regulatory measures which have led to a significant reduction of this type of pollution.

However, air pollution has not disappeared, but today it is of a different origin, with motorised transport as the primary source. In major towns and cities pollution peaks due to dense traffic affect the wellbeing of tens of thousands of people.

Epidemiological studies
In the early 1980s American researchers had already suggested that various forms of air pollution, even at moderate or low levels, could affect human health in the short term. In 1990 the European Commission decided to initiate concerted action on air pollutionrelated epidemiology. The aim was to improve the quality and effectiveness of research through largescale scientific cooperation. By financing coordinated action (reports, conferences, workshops, etc.) and thus consolidating the network of European epidemiology experts, this initiative has made it possible to establish standard test methods and ensure wide dissemination of research findings. It has formed the basis of scientific work which at has generated reliable quantitative estimates of the effects of air pollution on health on a European scale.

When pollution kills
APHEA (Air Pollution and Health - A European Approach) is one of the most important studies undertaken in this framework (11 teams of researchers from 10 EU countries). Its aim was to take stock of the shortterm effects of air pollution on the health of 25 million people living in 15 European cities. This operation was based on a meticulous analysis of statistical series correlating the pollution levels recorded with daily mortality and morbidity rates. According to Klea Katsouyanni, coordinator of the project, the advantage of this European approach, undertaken with a unique methodology in all the countries concerned, was that it focused on a number of sites with very different pollutant mixtures and greatly varying socioeconomic and environmental conditions.

Four main types of pollution were studied: suspended particles, SO2, nitrogen oxides and ozone. Widely reported in the scientific press but also in many other news media, the conclusions of the APHEA study (see table) have certainly not gone unnoticed. In a region such as Ile de France (the zone around Paris), for instance, sulphur dioxide and particle emissions (especially caused by diesel engines) lead to an excess mortality of more than 400 cases a year: between 260 to 350 deaths caused by cardiovascular accidents and 50 to 80 due to severe respiratory complications

International repercussion
All the pollutants studied affect human health, with a 50 g/m3 rise in pollutants accounting for a 23% increase in mortality. Klea Katsouyanni points out that what is particularly significant is that the pollution levels recorded for which correlations could be established were mostly below generally recognised international standards.

The findings of this research, widely disseminated, have given food for thought to both the European Commission in drafting the new directive on emissions of SO2, NO2 and particles, and the World Health Organisation in revising its guidelines for air quality in Europe.

While the APHEA programme has highlighted various effects of pollution on health, it has also raised a number of new questions. For instance, are there any regional differences - particularly in Central Europe where the impact on mortality appears to be less pronounced - and if so, why? What is the specific impact of each pollutant and is there any synergy between them? By how many years was the life of people who have died prematurely shortened due to the forms of pollution recorded?

To try and answer these questions a new APHEA 2 project started in February 1998. Extending cooperation, it now covers 34 cities in countries from Scandinavia to Turkey and Israel, and focuses on a larger number of pollutants.

Results of APHEA studies
Correlation established with
Type of pollution
Suspended particles
SO2 NOx Ozone
Total mortality
Deaths due to cardiovascular and respiratory problems
Hospital admissions of people with respiratory disorders (especially asthma)
(1) No correlation with admissions for asthma problems

A 50 g/m3 increase in the daily average level of acid particle pollution indicators (particles and SO2) is over the next few days followed by a 3% excess in daily total mortality. For photooxidant pollution (NO2, O3) this excess ranges from 1-3%. For specific mortality the 50 g/m3 increase in the level of pollution indicators correlates with a 1-4% excess in cardiovascular mortality and 4-5% for respiratory mortality.




Project Title:  
Short-term effects of air pollution on mortality and morbidity: a European approach using epidemiologic time-series data (APHEA)

Environment and climate

Contract Reference: EV5V-CT920202 (APHEA1) and ENV4-CT97-0534 (APHEA2)

CORDIS databaseFor more information on this project,
go to the Cordis database Record