Relationship between cotinine levels, household and personal smoking habit and season in 9-14 year old children.

The aim of this study was to determine the relationship of salivary cotinine levels with individual and household smoking habits and with the season in a sample (n = 146) of Italian schoolchildren aged 9-14 yrs. Active smoking and environmental tobacco smoke were measured by means of a confidential standardized interview with each participating child and by a self-reported questionnaire administered to the parents. Saliva samples were obtained twice: during winter from all children and during spring from a randomly selected subgroup. "Active smokers" were significantly more likely to be males and to live with smoking family members. Frequency of detectable cotinine both in "nonsmokers" and "active smokers" was significantly correlated with the number of cigarettes smoked by household members. However, for any level of smoking by parents detectable cotinine was more likely to be found in "active smokers" than in "nonsmokers". In "nonsmokers", the proportion of subjects with detectable cotinine decreased significantly in spring compared to winter, a finding not observed in "active smokers". In conclusion, we have demonstrated that passive smoking produces most effect in winter, and is linked to the amount and style of the parents' smoking, mainly related to smoking in presence of children. Conversely, salivary cotinine detected in spring appears to be derived mainly from active smoking.