title: A prospective study of the impact of air pollution on respiratory symptoms and infections in infants.
abstract: BACKGROUND
  There is increasing evidence that short-term exposure to air pollution has a detrimental effect on respiratory health, but data from healthy populations, particularly infants, are scarce.
  
  
  OBJECTIVE
  To assess the association of air pollution with frequency and severity of respiratory symptoms and infections measured weekly in healthy infants.
  
  
  METHODS
  In a prospective birth cohort of 366 infants of unselected mothers, respiratory health was assessed weekly by telephone interviews during the first year of life (19,106 total observations). Daily mean levels of particulate matter (PM10), nitrogen dioxide (NO2), and ozone (O3) were obtained from local monitoring stations. We determined the association of the preceding week's pollutant levels with symptom scores and respiratory tract infections using a generalized additive mixed model with an autoregressive component. In addition, we assessed whether neonatal lung function influences this association and whether duration of infectious episodes differed between weeks with normal PM10 and weeks with elevated levels.
  
  
  RESULTS
  We found a significant association between air pollution and respiratory symptoms, particularly in the week after respiratory tract infections (risk ratio, 1.13 [1.02-1.24] per 10 μg/m(3) PM10 levels) and in infants with premorbid lung function. During times of elevated PM10 (>33.3 μg/m(3)), duration of respiratory tract infections increased by 20% (95% confidence interval, 2-42%).
  
  
  CONCLUSIONS
  Exposure to even moderate levels of air pollution was associated with increased respiratory symptoms in healthy infants. Particularly in infants with premorbid lung function and inflammation, air pollution contributed to longer duration of infectious episodes with a potentially large socioeconomic impact.
authors.affiliation: Pediatric Respiratory Medicine, Inselspital, University of Bern, Bern, Switzerland.
authors.forename: Georgette
authors.initials: G
authors.lastname: Stern
authors.forename: Philipp
authors.initials: P
authors.lastname: Latzin
authors.forename: Martin
authors.initials: M
authors.lastname: Röösli
authors.forename: Oliver
authors.initials: O
authors.lastname: Fuchs
authors.forename: Elena
authors.initials: E
authors.lastname: Proietti
authors.forename: Claudia
authors.initials: C
authors.lastname: Kuehni
authors.forename: Urs
authors.initials: U
authors.lastname: Frey
mesh_terms: D000397:Air Pollution / Q000009:adverse effects*; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D011446:Prospective Studies; D012141:Respiratory Tract Infections / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*