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A 12-month study of PM10 and gases in the industrial Spanish town of Puertollano reveals striking variations in pollutant concentrations. The normal daily pollution pattern is characterised by a daily double peak for NO, and CO and associated double trough for ozone (morning and evening), a midday atmospheric fumigation peak for SO2 and PM10 (1-2 h later in winter), and a late morning through afternoon maximum for ozone (shorter and lower in winter). Superimposed upon this are: (1) seasonal variations, which accentuate the PM10 and SO2 mid-morning peaks in winter (when the peak occurs later than in summer), raise NO2, ozone and background particulate levels during the summer, and favour enhanced levels of NO during the winter; (2) local pollution spikes, particularly those associated with SO2 release from nearby industrial sources; (3) regional atmospheric stagnation episodes, which enhance concentrations of all pollutants and (4) intrusion of exotic pollutants, notably desert dust from North Africa. Given that air pollutants are known adversely to influence human health, understanding and predicting such diurnal variations in concentrations of inhalable pollutants is especially relevant to susceptible individuals such as asthmatics. (c) 2006 Elsevier Ltd. All rights reserved.