Smoke-free homes in England: prevalence, trends and validation by cotinine in children.

OBJECTIVE: To examine the prevalence of smoke-free homes in England between 1996 and 2007 and their impact on children's exposure to second-hand smoke via a series of annual cross-sectional surveys: the Health Survey for England. These comprised nationally representative samples of non-smoking children aged 4-15 (n = 13 365) and their parents interviewed in the home. Main outcome measures were cotinine measured in saliva, smoke-free homes defined by "no" response to "Does anyone smoke inside this house/flat on most days?", self-reported smoking status of parents and self-reported and cotinine validated smoking status in children.
RESULTS: The proportion of homes where one parent was a smoker that were smoke free increased from 21% in 1996 to 37% in 2007, and where both parents were smokers from 6% to 21%. The overwhelming majority of homes with non-smoking parents were smoke free (95% in 1996; 99% in 2007). For children with non-smoking parents and living in a smoke-free home the geometric mean cotinine across all years was 0.22 ng/ml. For children with one smoking parent geometric mean cotinine levels were 0.37 ng/ml when the home was smoke free and 1.67 ng/ml when there was smoking in the home; and for those with two smoking parents, 0.71 ng/ml and 2.46 ng/ml. There were strong trends across years for declines in cotinine concentrations in children in smoke-free homes for the children of smokers and non-smokers.
CONCLUSIONS: There has been a marked secular trend towards smoke-free homes, even when parents themselves are smokers. Living in a smoke-free home offers children a considerable, but not complete, degree of protection against exposure to parental smoking.