title: Exposure to NO2 and nitrous acid and respiratory symptoms in the first year of life.
abstract: BACKGROUND
  Effects of nitrogen dioxide (NO2) on respiratory health have been the subject of extensive research. The outcomes of these studies were not consistent. Exposure to nitrous acid, which is a primary product of combustion, and is also formed when NO2 reacts with water, may play an important role in respiratory health. We estimate the independent effects of exposure to nitrogen dioxide and nitrous acid on respiratory symptoms during the first year of life.
  
  
  METHODS
  Nitrogen dioxide and nitrous acid concentrations were measured once (1996-1998) in the homes of 768 infants who were at risk for developing asthma. Infants were living in southern New England. The frequency of respiratory symptoms in these children was recorded during the first year of life.
  
  
  RESULTS
  Infants living in homes with an NO2 concentration exceeding 17.4 ppb (highest quartile) had a higher frequency of days with wheeze (rate ratio = 2.2; 95% confidence interval = 1.4-3.4), persistent cough (1.8; 1.2-2.7), and shortness of breath (3.1; 1.8-5.6) when compared with infants in homes that had NO2 concentrations lower than 5.1 ppb (lowest quartile), controlling for nitrous acid concentration. Nitrous acid exposure was not independently associated with respiratory symptoms.
  
  
  CONCLUSIONS
  Among infants at risk for developing asthma, the frequency of reported respiratory symptoms in the first year of life was associated with levels of NO2 not currently considered to be harmful.
authors.affiliation: Yale School of Public Health, Center for Perinatal, Pediatric and Environmental Epidemiology, New Haven, Connecticut, USA. Robert.strien@med.uni-muenchen.de
authors.forename: Robert T
authors.initials: RT
authors.lastname: van Strien
authors.forename: Janneane F
authors.initials: JF
authors.lastname: Gent
authors.forename: Kathleen
authors.initials: K
authors.lastname: Belanger
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Triche
authors.forename: Michael B
authors.initials: MB
authors.lastname: Bracken
authors.forename: Brian P
authors.initials: BP
authors.lastname: Leaderer
mesh_terms: D016902:Air Pollution, Indoor / Q000009:adverse effects*; D001249:Asthma / Q000139:chemically induced / Q000453:epidemiology; D003237:Connecticut / Q000453:epidemiology; D003371:Cough / Q000139:chemically induced / Q000453:epidemiology; D004417:Dyspnea / Q000139:chemically induced / Q000453:epidemiology; D004781:Environmental Exposure / Q000009:adverse effects*; D006801:Humans; D007223:Infant; D007407:Interviews as Topic; D008404:Massachusetts / Q000453:epidemiology; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity*; D009608:Nitrous Acid / Q000032:analysis / Q000633:toxicity*; D012120:Respiration Disorders / Q000139:chemically induced* / Q000453:epidemiology; D012135:Respiratory Sounds; D018570:Risk Assessment
chemical_list: D009585:Nitrogen Dioxide; D009608:Nitrous Acid