article_snippet: Cotinine is a biomarker of passive smoke exposure.
article_snippet: Finnish researchers found that 84 per cent of children from households where neither parent smoked had non-detectable cotinine levels in Finnish researchers samples.
article_snippet: However, only 62 per cent of children from households where one parent smoked and 43 per cent of children from households where both parents smoked had blood samples with non-detectable cotinine levels.
article_snippet: Dr Costan Magnussen, of the University of Turku, said: 'Although we cannot confirm that children with a detectable blood cotinine in we was a result of passive smoke exposure directly from children with a detectable blood cotinine in our study parents, we know that a child's primary source of passive smoke exposure occurs at home. '