title: A longitudinal study of environmental tobacco smoke exposure in children: parental self reports versus age dependent biomarkers.
abstract: BACKGROUND
  Awareness of the negative effects of smoking on children's health prompted a decrease in the self-reporting of parental tobacco use in periodic surveys from most industrialized countries. Our aim is to assess changes between ETS exposure at the end of pregnancy and at 4 years of age determined by the parents' self-report and measurement of cotinine in age related biological matrices.
  
  
  METHODS
  The prospective birth cohort included 487 infants from Barcelona city (Spain). Mothers were asked about maternal and household smoking habit. Cord serum and children's urinary cotinine were analyzed in duplicate using a double antibody radioimmunoassay.
  
  
  RESULTS
  At 4 years of age, the median urinary cotinine level in children increased 1.4 or 3.5 times when father or mother smoked, respectively. Cotinine levels in children's urine statistically differentiated children from smoking mothers (Geometric Mean (GM) 19.7 ng/ml; 95% CI 16.83-23.01) and exposed homes (GM 7.1 ng/ml; 95% CI 5.61-8.99) compared with non-exposed homes (GM 4.5 ng/ml; 95% CI 3.71-5.48). Maternal self-reported ETS exposure in homes declined in the four year span between the two time periods from 42.2% to 31.0% (p < 0.01). Nevertheless, most of the children considered non-exposed by their mothers had detectable levels of cotinine above 1 ng/mL in their urine.
  
  
  CONCLUSIONS
  We concluded that cotinine levels determined in cord blood and urine, respectively, were useful for categorizing the children exposed to smoking and showed that a certain increase in ETS exposure during the 4-year follow-up period occurred.
authors.affiliation: Environmental and Pediatric Research Unit (URIE), Pediatric Department, Hospital del Mar, Barcelona, Spain. carmepuig@yahoo.es
authors.forename: Carme
authors.initials: C
authors.lastname: Puig
authors.forename: Oscar
authors.initials: O
authors.lastname: Garcia-Algar
authors.forename: Toni
authors.initials: T
authors.lastname: Monleon
authors.forename: Roberta
authors.initials: R
authors.lastname: Pacifici
authors.forename: Piergiorgio
authors.initials: P
authors.lastname: Zuccaro
authors.forename: Jordi
authors.initials: J
authors.lastname: Sunyer
authors.forename: Cecilia
authors.initials: C
authors.lastname: Figueroa
authors.forename: Simona
authors.initials: S
authors.lastname: Pichini
authors.forename: Oriol
authors.initials: O
authors.lastname: Vall
mesh_terms: D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood / Q000652:urine*; D002675:Child, Preschool; D015331:Cohort Studies; D003367:Cotinine / Q000097:blood / Q000652:urine*; D004781:Environmental Exposure / Q000032:analysis* / Q000517:prevention & control; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D009035:Mothers; D014028:Tobacco Smoke Pollution / Q000032:analysis*
chemical_list: D015415:Biomarkers; D014028:Tobacco Smoke Pollution; D003367:Cotinine