Study indicates children's exposure to secondhand smoke has decreased markedly since mid-nineties

The most comprehensive study to date of secondhand smoke exposure among children in England is published today in the journal Addiction. The study, carried out by researchers from the University of Bath's School for Health, reveals that exposure to household secondhand smoke among children aged 4-15 has declined steadily since 1996.

The researchers wanted to find out if there were ways to predict the levels of secondhand smoke encountered by children in private households, and whether those levels were changing over time. Using eight surveys conducted between 1996 and 2006, researchers took saliva samples from over 19,000 children aged 4-15 years. The saliva samples were analyzed for a substance called cotinine, an indicator of tobacco smoke exposure.

The results show that the average cotinine levels among non-smoking children declined by 59% from 1996 to 2006, indicating that children's exposure to secondhand smoke has decreased markedly since the mid-nineties. The researchers point out that the largest decline was between 2005 and 2006, a time of increased public debate and public information campaigns about secondhand smoke in the lead-up to the 2007 implementation of smoke-free legislation for public spaces.

The research also reveals that secondhand smoke exposure in non-smoking children is highest when one or both parents smoke, when the children are looked after by carers that smoke, and when smoking is allowed in the home. Dr Michelle Sims, first author of the paper, adds: "the importance of carer and parental smoking and household exposure tells us that reducing exposure in the home is the key to reducing the health risks associated with secondhand smoke exposure in children."

Dr Anna Gilmore, who led the project, said "this study shows that the factors which most strongly influence children's exposure are modifiable. Parents and carers can reduce their children's exposure to smoke by giving up smoking, or failing this, making a decision to smoke outside the house. Stopping others from smoking in their house is also important. The fact that children's exposure has already fallen so markedly shows that making these changes is feasible."

Sims M., Tomkins S., Judge K., Taylor G., Jarvis M.J., Gilmore A. "Trends in and predictors of secondhand smoke exposure indexed by cotinine in children in England from 1996-2006." Addiction 2010; 105: