title: Second-hand smoke exposure in 4-year-old children in Spain: Sources, associated factors and urinary cotinine.
abstract: BACKGROUND
  Second-hand smoke exposure (SHS) in children remains as a major pollution problem, with important consequences for children's health. This study aimed to identify the sources of exposure to SHS among 4-year-old children, comparing self-reports to a urinary biomarker of exposure, and characterize the most important variables related to SHS exposure in this population.
  
  
  METHODS
  4-year-old children's exposure to SHS was assessed by a parental-reported questionnaire and by urinary cotinine (UC) measurements in 1757 participants from 4 different areas of the Spanish INMA (INfancia y Medio Ambiente - Environment and Childhood) Project. The questionnaire about SHS included information about smoking habits at home by household members, and about exposure to SHS in other places including other homes, bars, restaurants or transportation. The association between quantified UC levels (>4ng/ml) and sociodemographic variables and the different sources of SHS exposure was examined using logistic regression.
  
  
  RESULTS
  Based on parental reports, 21.6% of the children were exposed to SHS at home and 47.1% elsewhere; making a total 55.9% of the children exposed to SHS. In addition, 28.2% of the children whose parents reported being not regularly exposed to SHS had quantified UC values. Children from younger mothers (<34 vs. ≥39.4 y) had a higher odds of exposure to SHS [OR (95% CI): 2.28 (1.70-3.05) per year], as well as from families with a lower educational level [OR secondary: 2.12 (1.69-2.65); primary or less: 2.91 (2.19-3.88)]. The odds of quantifiable UC in children dropped after the smoking ban in public places [OR=0.59 (0.42-0.83)]. Regarding the sources of SHS exposure we observed that quantifiable UC odds was increased in children whose parents smoked at home in their presence [OR mother occasionally: 13.39 (7.03-25.50); mother often: 18.48 (8.40-40.66); father occasionally: 10.98 (6.52-18.49); father often: 11.50 (5.96-22.20)] or in children attending other confined places, mainly other houses where people smoked [OR: 2.23 (1.78-2.80)].
  
  
  CONCLUSIONS
  Children's SHS exposure is nowadays an unresolved major public health problem in Spain. After the ban of smoking in public places health care professionals should put more emphasis to the parents on the importance of controlling the exposure of their children in private spaces.
authors.affiliation: Public Health Department, Basque Government, San Sebastian, Spain; University of the Basque Country (UPV/EHU), San Sebastian, Spain; Biodonostia Health Research Institute, San Sebastian, Spain. Electronic address: jj.aurreko@gmail.com.
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Aurrekoetxea
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; FISABIO-Universitat de València-Universitat Jaume I, Joint Research Unit, Av. Catalunya 21, 46020 Valencia, Spain. Electronic address: murcia_mar@gva.es.
authors.forename: Mario
authors.initials: M
authors.lastname: Murcia
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; FISABIO-Universitat de València-Universitat Jaume I, Joint Research Unit, Av. Catalunya 21, 46020 Valencia, Spain; Universitat Jaume I, Av. de Vicent Sos Baynat, s/n, 12071 Castelló de la Plana, Spain. Electronic address: murcia_mar@gva.es.
authors.forename: Marisa
authors.initials: M
authors.lastname: Rebagliato
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; Pompeu Fabra Universtiy, Barcelona, Spain; Center for Research in Environmental Epidemiology (CREAL), Barcelona, Spain; Department of Child and Adolescent Psychiatry/Psychology, Erasmus University Medical Centre - Sophia Children's Hospital, Rotterdam, The Netherlands. Electronic address: mguxens@creal.cat.
authors.forename: Mònica
authors.initials: M
authors.lastname: Guxens
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; Department of Preventive Medicine and Public Health, University of Oviedo, Oviedo, Spain. Electronic address: capua.uo@uniovi.es.
authors.forename: Ana
authors.initials: A
authors.lastname: Fernández-Somoano
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; Public Health Agency of Barcelona, Barcelona, Spain; Sant Pau Institute of Biomedical Research (IIB Sant Pau), Barcelona, Spain. Electronic address: mjlopez@aspb.cat.
authors.forename: María José
authors.initials: MJ
authors.lastname: López
authors.affiliation: University of the Basque Country (UPV/EHU), San Sebastian, Spain; Biodonostia Health Research Institute, San Sebastian, Spain. Electronic address: aitana.lertxundi@gmail.com.
authors.forename: Aitana
authors.initials: A
authors.lastname: Lertxundi
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; Public Health Laboratory, Basque Government, Spain. Electronic address: ANE_M2002@yahoo.es.
authors.forename: Ane Miren
authors.initials: AM
authors.lastname: Castilla
authors.affiliation: Public Health Laboratory, Basque Government, Spain. Electronic address: metabobi-san@ej-gv.es.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Espada
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; Department of Preventive Medicine and Public Health, University of Oviedo, Oviedo, Spain. Electronic address: atardon@uniovi.es.
authors.forename: Adonina
authors.initials: A
authors.lastname: Tardón
authors.affiliation: Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain; FISABIO-Universitat de València-Universitat Jaume I, Joint Research Unit, Av. Catalunya 21, 46020 Valencia, Spain. Electronic address: ballester_fer@gva.es.
authors.forename: Ferran
authors.initials: F
authors.lastname: Ballester
authors.affiliation: Public Health Department, Basque Government, San Sebastian, Spain; Biodonostia Health Research Institute, San Sebastian, Spain; Spanish Consortium for Research on Epidemiology and Public Health (CIBERESP), Spain. Electronic address: ambien4ss-san@ej-gv.es.
authors.forename: Loreto
authors.initials: L
authors.lastname: Santa-Marina
mesh_terms: D002675:Child, Preschool; D015331:Cohort Studies; D003367:Cotinine / Q000652:urine*; D003430:Cross-Sectional Studies; D004784:Environmental Monitoring / Q000379:methods*; D005260:Female; D006801:Humans; D019570:Inhalation Exposure / Q000032:analysis*; D008297:Male; D066252:Sociological Factors; D013030:Spain; D011795:Surveys and Questionnaires; D014028:Tobacco Smoke Pollution / Q000032:analysis*
chemical_list: D014028:Tobacco Smoke Pollution; D003367:Cotinine
keywords: Biological monitoring; Cotinine; Passive smoking; Preschool children; SHS