title: Changes in environmental tobacco smoke (ETS) exposure over a 20-year period: cross-sectional and longitudinal analyses.
abstract: OBJECTIVE
  To examine long-term changes in environmental tobacco smoke (ETS) exposure in British men between 1978 and 2000, using serum cotinine.
  
  
  METHODS
  Prospective cohort: British Regional Heart Study.
  
  
  METHODS
  General practices in 24 towns in England, Wales and Scotland.
  
  
  METHODS
  Non-smoking men: 2125 studied at baseline [questionnaire (Q1): 1978-80, aged 40-59 years], 3046 studied 20 years later (Q20: 1998-2000, aged 60-79 years) and 1208 studied at both times. Non-smokers were men reporting no current smoking with cotinine < 15 ng/ml at Q1 and/or Q20.
  
  
  METHODS
  Serum cotinine to assess ETS exposure.
  
  
  RESULTS
  In cross-sectional analysis, geometric mean cotinine level declined from 1.36 ng/ml [95% confidence interval (CI): 1.31, 1.42] at Q1 to 0.19 ng/ml (95% CI: 0.18, 0.19) at Q20. The prevalence of cotinine levels < or = 0.7 ng/ml [associated with low coronary heart disease (CHD) risk] rose from 27.1% at Q1 to 83.3% at Q20. Manual social class and northern region of residence were associated with higher mean cotinine levels both at Q1 and Q20; older age was associated with lower cotinine level at Q20 only. Among 1208 persistent non-smokers, cotinine fell by 1.47 ng/ml (95% CI: 1.37, 1.57), 86% decline. Absolute falls in cotinine were greater in manual occupational groups, in the Midlands and Scotland compared to southern England, although percentage decline was very similar across groups.
  
  
  CONCLUSIONS
  A marked decline in ETS exposure occurred in Britain between 1978 and 2000, which is likely to have reduced ETS-related disease risks appreciably before the introduction of legislation banning smoking in public places.
authors.affiliation: British Regional Heart Study, UCL Department of Primary Care and Population Sciences, Royal Free and University College Medical School, London, UK. b.jefferis@pcps.ucl.ac.uk
authors.forename: Barbara J
authors.initials: BJ
authors.lastname: Jefferis
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Thomson
authors.forename: Lucy T
authors.initials: LT
authors.lastname: Lennon
authors.forename: Colin
authors.initials: C
authors.lastname: Feyerabend
authors.forename: Mira
authors.initials: M
authors.lastname: Doig
authors.forename: Laura
authors.initials: L
authors.lastname: McMeekin
authors.forename: S Goya
authors.initials: SG
authors.lastname: Wannamethee
authors.forename: Derek G
authors.initials: DG
authors.lastname: Cook
authors.forename: Peter H
authors.initials: PH
authors.lastname: Whincup
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003367:Cotinine / Q000097:blood*; D003430:Cross-Sectional Studies; D004739:England; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011633:Public Facilities / Q000331:legislation & jurisprudence; D012606:Scotland; D012907:Smoking / Q000331:legislation & jurisprudence*; D014028:Tobacco Smoke Pollution / Q000032:analysis*; D014852:Wales
chemical_list: D015415:Biomarkers; D014028:Tobacco Smoke Pollution; D003367:Cotinine