title: Exposure to air pollution and respiratory symptoms during the first 7 years of life in an Italian birth cohort.
abstract: BACKGROUND
  Ambient air pollution has been consistently associated with exacerbation of respiratory diseases in schoolchildren, but the role of early exposure to traffic-related air pollution in the first occurrence of respiratory symptoms and asthma is not yet clear.
  
  
  METHODS
  We assessed the association between indexes of exposure to traffic-related air pollution during different periods of life and respiratory outcomes in a birth cohort of 672 newborns (Rome, Italy). Direct interviews of the mother were conducted at birth and at 6, 15 months, 4 and 7 years. Exposure to traffic-related air pollution was assessed for each residential address during the follow-up period using a Land-Use Regression model (LUR) for nitrogen dioxide (NO2) and a Geographic Information System (GIS) variable of proximity to high-traffic roads (HTR) (>10 000vehicles/day). We used age-specific NO2 levels to develop indices of exposure at birth, current, and lifetime time-weighted average. The association of NO2 and traffic proximity with respiratory disorders were evaluated using logistic regression in a longitudinal approach (Generalised Estimating Equation). The exposure indexes were used as continuous and categorical variables (cut-off points based on the 75th percentile for NO2 and the 25th percentile for distance from HTRs).
  
  
  RESULTS
  The average NO2 exposure level at birth was 37.2 μg/m(3) (SD 7.2, 10-90th range 29.2-46.1). There were no statistical significant associations between the exposure indices and the respiratory outcomes in the longitudinal model. The odds ratios for a 10-µg/m(3) increase in time-weighted average NO2 exposure were: asthma incidence OR=1.09; 95 CI% 0.78 to 1.52, wheezing OR=1.07; 95 CI% 0.90 to 1.28, shortness of breath with wheezing OR=1.16; 95 CI% 0.94 to 1.43, cough or phlegm apart from cold OR=1.11; 95 CI% 0.92 to 1.33, and otitis OR=1.08; 95 CI% 0.89 to 1.32. Stronger but not significant associations were found considering the 75th percentile of the NO2 distribution as a cut-off, especially for incidence of asthma and prevalence of wheeze (OR=1.41; 95 CI% 0.88 to 2.28 and OR=1.27; 95 CI% 0.95 to 1.70, respectively); the highest OR was found for wheezing (OR=2.29; 95 CI% 1.15 to 4.56) at the 7-year follow-up. No association was found with distance from HTRs.
  
  
  CONCLUSIONS
  Exposure to traffic-related air pollution is only weakly associated with respiratory symptoms in young children in the first 7 years of life.
authors.affiliation: Environmental Health Reference Centre, Regional Agency for Environmental Prevention of Emilia-Romagna, Modena, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ranzi
authors.forename: Daniela
authors.initials: D
authors.lastname: Porta
authors.forename: Chiara
authors.initials: C
authors.lastname: Badaloni
authors.forename: Giulia
authors.initials: G
authors.lastname: Cesaroni
authors.forename: Paolo
authors.initials: P
authors.lastname: Lauriola
authors.forename: Marina
authors.initials: M
authors.lastname: Davoli
authors.forename: Francesco
authors.initials: F
authors.lastname: Forastiere
mesh_terms: D000328:Adult; D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D000397:Air Pollution / Q000009:adverse effects* / Q000032:analysis; D001249:Asthma / Q000209:etiology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003371:Cough / Q000209:etiology; D004417:Dyspnea / Q000209:etiology; D004781:Environmental Exposure / Q000009:adverse effects* / Q000032:analysis; D004784:Environmental Monitoring / Q000379:methods; D005260:Female; D040362:Geographic Information Systems; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D007407:Interviews as Topic; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D009585:Nitrogen Dioxide / Q000032:analysis; D016017:Odds Ratio; D010031:Otitis / Q000209:etiology; D015995:Prevalence; D012120:Respiration Disorders / Q000209:etiology*; D012135:Respiratory Sounds / Q000209:etiology; D012384:Rome; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000393:Air Pollutants; D001335:Vehicle Emissions; D009585:Nitrogen Dioxide
keywords: Exposure assessment < Methodology, speciality; Land Use Regression Model; Pollution < Materials, exposures and occupational groups