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. 2012 Mar 21;67(8):682–688. doi: 10.1136/thoraxjnl-2011-200391

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© 2012, Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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Relationships between air pollutants in classrooms and past year asthma in the entire sample population of schoolchildren (N=6590) of the 6 Cities Study. Tertiles are defined according to the distribution of air pollutants in the classrooms (in μg/m³). Nitrogen dioxide (NO₂): low ≤23.7, medium >23.7 to ≤31.6, high >31.6; fine particles with aerodynamic diameter ≤2.5 μm (PM_2.5): low ≤12.2, medium >12.2 to ≤17.5, high >17.5; formaldehyde: low ≤19.1, medium >19.1 to ≤28.4, high >28.4; acetaldehyde: low ≤6.5, medium >6.5 to ≤9.9, high >9.9; acrolein: low=limit of detection (LD), medium >LD to ≤1.55, high >1.55. Dots are OR adjusted for age, gender, passive smoking and paternal or maternal history of asthma and allergic diseases; bars are 95% CIs.