Onset and remission of childhood wheeze and rhinitis across China — Associations with early life indoor and outdoor air pollution

Few longitudinal studies exist on childhood exposure to indoor and outdoor air pollution and respiratory illness in China. We studied associations between indoor and outdoor environment and prevalence, onset and remission of wheeze and rhinitis among children across China.Children (3-6 y) were recruited from randomized day care centres in six cities. The main data analysis was restricted to children not moving since birth (N = 17,679). Data on wheeze, rhinitis and the home environment were assessed by a parental questionnaire. Prevalence in the first two years of life (baseline) and the last year (follow-up) was used to calculate onset and remission. Outdoor PM2.5, PM10, and NO2 at the day care centre were modelled from monitoring station data. Associations were calculated by multilevel logistic regression.Prenatal NO2 was associated with decreased remission of wheeze and increased prevalence and increased onset of rhinitis. Prenatal PM2.5 was associated with increased prevalence of wheeze. Postnatal NO2 and postnatal PM10 were associated with increased prevalence and lower remission of wheeze and rhinitis. Mould, window pane condensation, renovation and cockroaches at home were associated with increased prevalence and increased onset of wheeze and rhinitis. Gas cooking was associated with increased onset of rhinitis. Children of mothers with industrial work had more wheeze.Outdoor PM2.5, PM10 and NO2 can increase childhood wheeze and rhinitis. Dampness and mould can increase onset and decrease remission. Crowdedness, cockroaches at home and emissions from new building materials and gas cooking can be risk factors for wheeze and rhinitis.