Effectiveness of smoke-free legislation on second hand smoke exposure of children : a systematic review

Abstract

Background: The tobacco epidemic causes a major burden to long-term global public health. Second hand smoke is one of the modifiable exposures causing adverse health effects to children; 40% of children in the world are regularly exposed to second hand smoke and children account for more than a quarter of all deaths from second hand smoke exposure. The global burden highlights the importance of implementation and enforcement of comprehensive smoke-free legislation. Despite smoke-free legislation having been shown to have a positive effect in reducing the prevalence of tobacco consumption and second hand smoke exposure, displacement of smoking from enclosed public places to homes after implementation of smoke-free legislation might increase second hand smoke exposure in children.

Objectives: This systematic review aims to investigate the effect of smoke-free legislation on second hand smoke exposure in children and to explore the potential risk factors that may affect its effectiveness.

Methods: Studies were searched in online electronic databases, PubMed and EMBASE Classic+ EMBASE 1980-via Ovid (from 1980 to 2014) under the Library website of the University of Hong Kong, by keyword search, hand search of references and Google Scholar for relevant articles published from 2004 to present. Observational studies assessing the effect of smoke-free legislation on second hand smoke exposure in children assessed from cotinine measured before and after the introduction of smoke-free legislation were included.

Results: This systematic reviewed identified 8 relevant studies. 3 were assessed as good quality and 5 as average quality. All selected studies reported a decrease in the geometric mean of cotinine concentration after the implementation of smoke-free legislation, but only one of them showed that the reduction in cotinine concentration was significantly reduced from 0.3ng/ml to 0.2ng/ml. An increase in the percentage of cotinine concentrations below the limit of detection and a decrease in the percentage of harmful levels of cotinine concentration were also found. Lower socioeconomic status, more parental smokers and low level of home smoking restriction affected the reduction in second hand smoke exposure after implementation of smoke-free legislation.

Conclusion: Smoke-free legislation has a positive effect towards reduction in second hand smoke exposure in children. There is no evidence supporting the possibility that smokers displace tobacco consumption from public areas to their homes after implementation of smoke-free legislation in Western settings. Whether more effort to encourage smoking cessation among parents and other family members living with children would be particularly effective in reducing the public health burden of tobacco consumption should be investigated. Further tobacco control strategies are suggested to work comprehensively with smoke-free legislation to further reduce the global burden of tobacco epidemic.