title: Outdoor, but not indoor, nitrogen dioxide exposure is associated with persistent cough during the first year of life.
abstract: OBJECTIVE
  Because their lungs and immune system are not completely developed, children are more susceptible to respiratory disease and more vulnerable to ambient pollution. We assessed the relation between prenatal and postnatal nitrogen dioxide (NO(2)) levels and the development of lower respiratory tract infections (LRTI), wheezing and persistent cough during the first year of life.
  
  
  METHODS
  The study population consisted of 352 children from a birth cohort in Valencia, Spain. Prenatal exposure to NO(2), a marker of traffic related air pollution was measured at 93 sampling sites spread over the study area during four different sampling periods of 7 days each. It was modeled for each residential address through land use regression using the empirical measurements and data from geographic information systems. Postnatal exposure was measured once inside and outside each home using passive samplers for a period of 14 days. Outcomes studied were any episode of LRTI during the child's first year of life diagnosed by a doctor (bronchitis, bronchiolitis or pneumonia), wheezing (defined as whistling sounds coming from the chest), and persistent cough (more than three consecutive weeks). Outcomes and potential confounders were obtained from structured questionnaires. Multiple logistic regression was used to identify associations.
  
  
  RESULTS
  The cumulative incidence (CI) at first year of life was 30.4% for LRTI (23.0% bronchiolitis, 11.9% bronchitis and 1.4% pneumonia), 26.1% for wheezing and 6.3% for persistent cough. The adjusted odds ratio (95% confidence interval) per 10μg/m(3) increment in postnatal outdoor NO(2) concentration was 1.40 (1.02-1.92) for persistent cough. We also found some pattern of association with LRTI, bronchiolitis, bronchitis, wheezing and persistent cough in different prenatal periods, although it was not statistically significant.
  
  
  CONCLUSIONS
  Our results indicate that exposure to outdoor, but not indoor, NO(2) during the first year of life increases the risk of persistent cough.
authors: CIBER Epidemiología y Salud Pública, Spain. esplugues_ana@gva.es
authors: Ana
authors: A
authors: Esplugues
authors: Ferran
authors: F
authors: Ballester
authors: Marisa
authors: M
authors: Estarlich
authors: Sabrina
authors: S
authors: Llop
authors: Virginia
authors: V
authors: Fuentes-Leonarte
authors: Enrique
authors: E
authors: Mantilla
authors: Jesús
authors: J
authors: Vioque
authors: Carmen
authors: C
authors: Iñiguez
mesh_terms: D003371:Cough / Q000453:epidemiology* / Q000209:etiology; D004781:Environmental Exposure / Q000032:analysis*; D005260:Female; D040362:Geographic Information Systems; D006801:Humans; D015994:Incidence; D007223:Infant; D016015:Logistic Models; D008962:Models, Theoretical; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012135:Respiratory Sounds / Q000209:etiology; D012141:Respiratory Tract Infections / Q000453:epidemiology* / Q000209:etiology; D013030:Spain; D011795:Surveys and Questionnaires; D001335:Vehicle Emissions / Q000032:analysis / Q000633:toxicity*
chemical_list: D001335:Vehicle Emissions; D009585:Nitrogen Dioxide