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Changes in child exposure to environmental tobacco smoke (CHETS) study after implementation of smoke-free legislation in Scotland: national cross sectional survey

BMJ 2007; 335 doi: (Published 13 September 2007) Cite this as: BMJ 2007;335:545
  1. Patricia C Akhtar, research fellow1,
  2. Dorothy B Currie, senior statistician1,
  3. Candace E Currie, director1,
  4. Sally J Haw, principal public health adviser2
  1. 1Child and Adolescent Health Research Unit (CAHRU), University of Edinburgh, Edinburgh EH8 8AQ
  2. 2NHS Health Scotland, Edinburgh EH12 5EZ
  1. Correspondence to: P C Akhtar patricia.akhtar{at}
  • Accepted 15 August 2007


Objective To detect any change in exposure to secondhand smoke among primary schoolchildren after implementation of smoke-free legislation in Scotland in March 2006.

Design Comparison of nationally representative, cross sectional, class based surveys carried out in the same schools before and after legislation.

Setting Scotland.

Participants 2559 primary schoolchildren (primary 7; mean age 11.4 years) surveyed in January 2006 (before smoke-free legislation) and 2424 in January 2007 (after legislation).

Outcome measures Salivary cotinine concentrations, reports of parental smoking, and exposure to tobacco smoke in public and private places before and after legislation.

Results The geometric mean salivary cotinine concentration in non-smoking children fell from 0.36 (95% confidence interval 0.32 to 0.40) ng/ml to 0.22 (0.19 to 0.25) ng/ml after the introduction of smoke-free legislation in Scotland—a 39% reduction. The extent of the fall in cotinine concentration varied according to the number of parent figures in the home who smoked but was statistically significant only among pupils living in households in which neither parent figure smoked (51% fall, from 0.14 (0.13 to 0.16) ng/ml to 0.07 (0.06 to 0.08) ng/ml) and among pupils living in households in which only the father figure smoked (44% fall, from 0.57 (0.47 to 0.70) ng/ml to 0.32 (0.25 to 0.42) ng/ml). Little change occurred in reported exposure to secondhand smoke in pupils' own homes or in cars, but a small decrease in exposure in other people's homes was reported. Pupils reported lower exposure in cafes and restaurants and in public transport after legislation.

Conclusions The Scottish smoke-free legislation has reduced exposure to secondhand smoke among young people in Scotland, particularly among groups with lower exposure in the home. We found no evidence of increased secondhand smoke exposure in young people associated with displacement of parental smoking into the home. The Scottish smoke-free legislation has thus had a positive short term impact on young people's health, but further efforts are needed to promote both smoke-free homes and smoking cessation.


  • We thank ABS Labs, London, who analysed salivary cotinine; MVA Consultancy for managing the fieldwork; Scottish local education authorities for granting permission to approach schools under their authority; pupils and teachers of all participating schools; Emily Healy, research administrator, Child and Adolescent Health Research Unit (CAHRU) for providing assistance with this paper; Kate Levin (CAHRU), Joanna Todd (CAHRU), and Rebecca Smith (CAHRU) for providing useful comments on drafts of this paper; and independent reviewers for providing comments on this paper.

  • Contributors: PCA participated in research design, managed the CHETS survey, prepared study materials, analysed the data, interpreted the data analysis, and led the preparation of drafts of the manuscript. DBC participated in research design, data analysis, interpretation of data analysis, and preparation of drafts of the manuscript. CEC, as principal investigator, is the guarantor. She participated in research design, interpretation of data analysis, and preparation of drafts of the manuscript. SJH participated in research design and preparation of drafts of the manuscript.

  • Funding: NHS Health Scotland and the Scottish Executive. The study design was developed in discussion with an advisory group that included SJH (NHS Health Scotland). The timing of submission of this paper was agreed with the sponsor, as it would form part of a portfolio of other papers submitted simultaneously. SJH contributed to preparation of the manuscript, but this did not create any conflicts of interest.

  • Competing interests: None declared.

  • Ethical approval: School of Education Ethics Committee, University of Edinburgh.

    Provenance and peer review: Non-commissioned; externally peer reviewed.

  • Accepted 15 August 2007
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