Trends in and predictors of second-hand smoke exposure indexed by cotinine in children in England from 1996 to 2006

Aims To explore trends in and predictors of second-hand smoke (SHS) exposure in children. To identify whether inequalities in SHS exposure are changing over time. Design Repeated cross-sectional study with data from eight annual surveys conducted over an 11-year period from 1996 to 2006. Setting England. Participants Nationally representative samples of children aged 4-15 years living in private households. Measurements Saliva cotinine (4-15-year-olds), current smoking status (8-15-year-olds), smoking status of parents and carers, smoking in the home, socio-demographic variables. Findings The most important predictors of SHS exposure were modifiable factors-whether people smoke in the house on most days, whether the parents smoke and whether the children are looked after by carers who smoke. Children from more deprived households were more exposed and this remained the case even after parental smoking status has been controlled for. Exposure over time has fallen markedly among children (59% decline over 11 years in geometric mean cotinine), with the most marked decline observed in the period immediately preceding smoke-free legislation. Declines in exposure have generally been greater in children most exposed at the outset. For example, in children whose parents both smoke, median cotinine declined annually by 0.115 ng/ml compared with 0.019 ng/ml where neither parent smokes (P < 0.05). Conclusions In the 11 years leading up to smoke-free legislation in England, the overall level of SHS exposure in children as well as absolute inequalities in exposure have been declining. Further efforts to encourage parents and carers to quit and to avoid smoking in the home would benefit child health