[Short-term effects of exposure to urban air pollution on human health in Europe. The APHEA Projects (Air Pollution and Health: a European Approach].

During the '80s, evidence was collected that air pollutants concentrations close to, or lower than, air quality standards could negatively influence public health at short term, i.e. within a few days. The European Union financed, between 1993 and 1995, the study "Short term effects of Air Pollution on Health: a European Approach using epidemiological time-series data" (APHEA-1 project), involving more than 25 millions inhabitants in 15 cities, investigated between 1977 and 1991. In this paper, the main results, already published in various scientific journals, are reported. The health effects were studied as mortality for natural causes, cardiovascular and respiratory diseases, and as emergency hospital admissions for all respiratory diseases, bronchial asthma, and chronic obstructive pulmonary disease (COPD). The pollutants whose measures were available for the analysis are sulphur dioxide (SO2), nitrogen dioxide (NO2), particulate matter (PM) measured either as black smoke or total suspended particulate, and ozone (O3). The analysis was carried out by each participating group following a detailed protocol, defined during various workshops, through the construction of Poisson regression models, adjusted for autocorrelation and overdispersion, accounting for variables influencing the daily count of deaths, such as long time trends, season, temperature, day of the week. This paper reports the results of the meta-analysis, performed using the values of each city, as relative risk of dying or being admitted to hospital associated with increases of 50 micrograms/m3 in the 24 hours average concentrations of each pollutant. The daily number of natural deaths was associated with increases in the levels of PM, SO2, O3, and NO2. Cardiovascular and respiratory deaths were associated with increases of the levels of PM, SO2, and O3; cardiovascular deaths were associated also with increases of NO2 concentrations. Emergency hospital admissions for the whole group of respiratory disorders are less consistently associated with PM, SO2, and NO2, whereas there is evidence of association with O3. COPD admissions are related to the air pollutant levels, especially those of O3. Lastly, NO2 levels may play a role in exhacerbating asthma, and SO2 levels can have an effect on asthma in children. A second study is currently going on, involving over 40 millions residents in 34 cities. The aims of this project are: to evaluate the dose-response relationship, to investigate on synergy among pollutants, on the "harvesting" phenomenon, on the geographical differences inside Europe and with the U.S. through the collaboration with a similar American study now in progress. The existence of an association between daily variations in the levels of urban air pollution and adverse health effects was confirmed in Europe. This association is weak, but it involves the whole resident population, so it is a major cause of concern from the public health point of view.