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

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