Factors determining exposure to passive smoking in young adults living at home: quantitative analysis using saliva cotinine concentrations.

Saliva cotinine concentrations were used to examine determinants of exposure to environmental tobacco smoke in 393 non-smoking students (age range 16-19 years) attending a sixth form college and living at home. Average concentrations were low (median 0.60 ng/ml), reflecting partly the warm weather at the time of the survey and partly the predominantly middle class sample. Despite this, cotinine levels were strongly related to the extent of self-reported passive smoking in the past three days (medians 0.30, 0.60, 0.90 and 1.35 ng/ml in those reporting 'None at all', 'A little', 'Some' and 'A lot' respectively, p less than 0.0001). Individual sources of environmental tobacco smoke identified were smoking by mothers (p less than 0.0001), by fathers (p less than 0.01), and exposure at college (p less than 0.001) and when out in the evenings (p less than 0.001). The results indicate that exposure outside the home may become of equal or greater importance than family smoking in determining the overall passive smoking dose received by this age group.