[Asthma, urban atmospheric pollution and the weather].

The aim of this study, which was carried out in an urban environment, was to research in to a possible relationship between temporal variations in the level of atmospheric pollution in the centre of Paris, compared to the frequency of acute dyspnoeic crises in which asthmatic patients had requested the emergency service (SOS Médecins). This study began in the first half of 1989; during this period there were 701 cases of acute asthma recorded within the Paris city boundary by "SOS Médecins". The pollutants recorded were sulphur dioxide (SO2), an index of black smoke (FN), oxides of nitrogen (NOx), ozone (O3) and soluble sulphate particles (SO4). In addition, the weather patterns were examined and pollen counts were recorded. In spite of a sub-acute episode of pollution in January and February, there was no definite increase noted in the number of emergency calls made for acute asthma. In the first three months, the number of crises were, on average, higher in association with high levels of the principal pollutants (SO2 FN, NOx, SO4) as well as with the periods of high atmospheric pressure; however, only the sulphate content and atmospheric pressure remained correlated with the daily number of asthmatic crises. In the second three months, there were some co-variations uniquely associated with sulphate particles, the atmospheric pressure, and above all the ozone level (allowing for a gap of one day). The influence of the daily variations in total pollen content or of grass pollens did not show up in this study.