Active and passive tobacco smoke exposure: a comparison of maternal and child hair cotinine levels.

The objective of this study was to compare tobacco smoke exposure in mothers and their healthy children less than 3 years old using hair cotinine (HC) levels as an objective long-term measure of exposure. Hair samples were obtained from mother/child pairs recruited from the Columbus Children's Hospital Primary Care Center, and were analyzed by radioimmunoassay to compare HC levels. Mothers were both self-reported smokers and nonsmokers. Contributing and confounding variables were assessed based on questionnaires completed by participants. Exclusion criteria for children were prematurity and presence of chronic cardiopulmonary disease. Hair samples and questionnaires were obtained from 104 mother/child pairs. Child and maternal HC levels were correlated for both self-reported maternal smokers (R2 = .13, p < .013) and self-reported maternal nonsmokers (R2 = .54, p < 001). Child HC levels were higher than maternal HC levels (1.18 ng/mg vs. .78 ng/mg, p < .001). Children of nonsmokers had higher HC levels than their mothers (.77 ng/mg vs. .35 ng/mg, p < .001), while HC levels of smokers and their children were no different (1.91 ng/mg vs. 1.92 ng/mg, p = .978). The relationship between child and maternal HC did not differ by child age, gender, or race. In conclusion, environmental tobacco smoke exposure in young children as reflected by HC is higher than expected based on prior studies of biomarkers and passive tobacco smoke exposure in adult nonsmokers.