title: Passive exposure to tobacco smoke in children aged 5-7 years: individual, family, and community factors.
abstract: OBJECTIVE
  To examine the importance of parental smoking on passive exposure to tobacco smoke in children and the social and geographical patterns of exposure.
  
  
  METHODS
  Cross sectional study.
  
  
  METHODS
  Schools in 10 towns in England and Wales; five towns with high adult cardiovascular mortality and five with low rates.
  
  
  METHODS
  4043 children aged 5-7 years of European origin.
  
  
  METHODS
  Salivary cotinine concentration and parents self reported smoking habits.
  
  
  RESULTS
  1061 (53.0%) children were exposed to cigarette smoke at home or by an outside carer. Geometric mean cotinine rose from 0.29 (95% confidence interval 0.28 to 0.31) ng/ml in children with no identified exposure to 4.05 (3.71 to 4.42) ng/ml in households where both parents smoked and 9.03 (6.73 to 12.10) ng/ml if both parents smoked more than 20 cigarettes a day. The effect of mothers' smoking was greater than that of fathers', especially at high levels of consumption. After adjustment for known exposures geometric mean cotinine concentrations rose from 0.52 ng/ml in social class I to 1.36 ng/ml in social class V (P < 0.0001); and were doubled in high mortality towns compared with the low mortality towns (P = 0.002). In children with no identified exposure similar trends by social class and town were observed and the cotinine concentrations correlated with the prevalence of parental smoking, both between towns (r = 0.69, P = 0.02) and between schools within towns (r = 0.50, P < 0.001).
  
  
  CONCLUSIONS
  Mothers' smoking is more important that fathers' despite the lower levels of smoking by mothers. Children not exposed at home had low cotinine concentration, the level depending on the prevalence of smoking in the community.
authors.affiliation: Department of Public Health Sciences, St George's Hospital, Medical School, London.
authors.forename: D G
authors.initials: DG
authors.lastname: Cook
authors.forename: P H
authors.initials: PH
authors.lastname: Whincup
authors.forename: M J
authors.initials: MJ
authors.lastname: Jarvis
authors.forename: D P
authors.initials: DP
authors.lastname: Strachan
authors.forename: O
authors.initials: O
authors.lastname: Papacosta
authors.forename: A
authors.initials: A
authors.lastname: Bryant
mesh_terms: D000367:Age Factors; D002648:Child; D003367:Cotinine / Q000032:analysis*; D003430:Cross-Sectional Studies; D004739:England / Q000453:epidemiology; D004781:Environmental Exposure; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D010290:Parents; D012111:Residence Characteristics; D012463:Saliva / Q000737:chemistry; D012574:Schools; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D012923:Social Class; D014028:Tobacco Smoke Pollution; D014852:Wales / Q000453:epidemiology
chemical_list: D014028:Tobacco Smoke Pollution; D003367:Cotinine