In the October issue of Thorax, Leonardi-Bee et al reviewed the effects of parental smoking on the uptake of smoking by children.1 They conclude that exposure to smoking within the family is a significant determinant of subsequent smoking.

One area that this study did not address was the effect of the site of the smoking on exposure.

We have studied urinary cotinine levels in children attending an asthma clinic and correlated them with the self-reported smoking habits of their carers. Thirty-six girls and 64 boys aged between …