PM10 and children's respiratory symptoms and lung function in the PATY study

Studies of the impact of long-term exposure to outdoor air pollution on prevalence of respiratory symptoms and lung function in children have yielded mixed results, partly related to differences in study design, exposure assessment, confounder selection and data analysis.We assembled respiratory health and exposure data for more than 45,000 children from comparable cross-sectional studies in 12 countries. Eleven respiratory symptoms were selected for which comparable questions were asked. Spirometry was performed in about half of the children. Exposure to air pollution was mainly characterized by annual average concentrations of particulate matter smaller than 10 mum (PM10) measured at fixed sites within the study areas.Positive associations were found between the average PM10 concentration and the prevalence of phlegm (Odds Ratio per 10 mug.m(-3) 1.15, 95% Confidence Interval 1.02-1.30), hay fever (1.20 (0.99-1.46)), bronchitis (1.08 (0.98-1.19)), morning cough (1.15 (1.02-1.29)) and nocturnal cough (1.13 (0.98-1.29)). There were no associations with diagnosed asthma and asthma symptoms. PM10 was not associated with lung function across all studies combined.Our study adds to the evidence that long-term exposure to outdoor air pollution, characterized by the concentration of PM10, is associated with increased respiratory symptoms