Relative risks of incident bronchitis and asthma by pulmonary function indices, stratified by community-specific annual average NO₂ levels (2007–2009).

a<p>FVC, forced vital capacity; FEV₁, forced expiratory volume in 1s; MMEF, forced expiratory flow over the mid-range of expiration.</p>b<p>Two NO₂ strata were defined as less than and greater than the median level (17.5 ppb).</p>c<p>Relative risks (RR) and 95% confidence intervals (CI) of outcomes were scaled across the inter-quartile range elevation by each pulmonary function index.</p><p>All models were adjusted for community, <i>in utero</i> exposure to maternal smoking, family history of asthma, family history of atopy, active smoking and current SHS.