title: Air pollution, fetal and infant tobacco smoke exposure, and wheezing in preschool children: a population-based prospective birth cohort.
abstract: BACKGROUND
  Air pollution is associated with asthma exacerbations. We examined the associations of exposure to ambient particulate matter (PM10) and nitrogen dioxide (NO2) with the risk of wheezing in preschool children, and assessed whether these associations were modified by tobacco smoke exposure.
  
  
  METHODS
  This study was embedded in the Generation R Study, a population-based prospective cohort study among 4,634 children. PM10 and NO2 levels were estimated for the home addresses using dispersion modeling. Annual parental reports of wheezing until the age of 3 years and fetal and infant tobacco smoke exposure was obtained by questionnaires.
  
  
  RESULTS
  Average annual PM10 or NO2 exposure levels per year were not associated with wheezing in the same year. Longitudinal analyses revealed non-significant tendencies towards positive associations of PM10 or NO2 exposure levels with wheezing during the first 3 years of life (overall odds ratios (95% confidence interval): 1.21 (0.79, 1.87) and 1.06 (0.92, 1.22)) per 10 μg/m3 increase PM10 and NO2, respectively). Stratified analyses showed that the associations were stronger and only significant among children who were exposed to both fetal and infant tobacco smoke (overall odds ratios 4.54 (1.17, 17.65) and 1.85 (1.15, 2.96)) per 10 μg/m3 increase PM10 and NO2, respectively (p-value for interactions <0.05).
  
  
  CONCLUSIONS
  Our results suggest that long term exposure to traffic-related air pollutants is associated with increased risks of wheezing in children exposed to tobacco smoke in fetal life and infancy. Smoke exposure in early life might lead to increased vulnerability of the lungs to air pollution.
authors.affiliation: Department of Pediatrics, Division of Respiratory Medicine, Erasmus Medical Center, Rotterdam, The Netherlands.
authors.forename: Agnes M M
authors.initials: AM
authors.lastname: Sonnenschein-van der Voort
authors.forename: Yvonne
authors.initials: Y
authors.lastname: de Kluizenaar
authors.forename: Vincent W V
authors.initials: VW
authors.lastname: Jaddoe
authors.forename: Carmelo
authors.initials: C
authors.lastname: Gabriele
authors.forename: Hein
authors.initials: H
authors.lastname: Raat
authors.forename: Henriëtte A
authors.initials: HA
authors.lastname: Moll
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Frank H
authors.initials: FH
authors.lastname: Pierik
authors.forename: Henk Me
authors.initials: HM
authors.lastname: Miedema
authors.forename: Johan C
authors.initials: JC
authors.lastname: de Jongste
authors.forename: Liesbeth
authors.initials: L
authors.lastname: Duijts
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000633:toxicity*; D002675:Child, Preschool; D005260:Female; D005333:Fetus; D006801:Humans; D007223:Infant; D008297:Male; D008431:Maternal-Fetal Exchange; D009426:Netherlands / Q000453:epidemiology; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity*; D052638:Particulate Matter / Q000032:analysis / Q000633:toxicity*; D011247:Pregnancy; D011446:Prospective Studies; D012135:Respiratory Sounds / Q000209:etiology*; D012307:Risk Factors; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*; D001335:Vehicle Emissions
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter; D014028:Tobacco Smoke Pollution; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide