URINARY COTININE IN CHILDREN AND ADULTS DURING AND AFTER SEMIEXPERIMENTAL EXPOSURE TO ENVIRONMENTAL TOBACCO-SMOKE

Urinary cotinine (U-cotinine) as a biomarker of environmental tobacco smoke exposure was evaluated in 14 children (age 4-11 y) and in 7 adul ts who were exposed to environmental tobacco smoke at an air nicotine level of 110 mg/m3 for 2 h in a bus. Nicotine in air and U-cotinine we re measured by gas chromatography/mass spectrometry before, during, an d after the experiment. U-cotinine rose rapidly to a maximum after a m edian of 6 h following the end of exposure; remained at an apparent pl ateau for half a day; and then decreased exponentially, with a mean ha lf-time of 19 h (95% confidence interval 18-20 h; no significant diffe rence between children and adults). The maximum U-cotinine was higher in the children (mean = 22 mg/l) than in the adults (13 mg/l; p = .005 ); decreased with age among the children (r = -.74; p = .002); and inc reased as the estimated inhaled nicotine dose increased. Therefore, th e findings of the present study showed that young children had higher U-cotinine than adults at the same experimental environmental tobacco smoke exposure, probably because they had a higher relative nicotine d ose because of a higher relative ventilation rate, and possibly also b ecause of metabolic differences; the elimination rate did not differ, The long half-time makes U-cotinine a good biomarker of environmental tobacco smoke exposure; the time of sampling is not very critical. Dil ution-adjusted concentrations should be employed, and in children, pre ferably by density correction. A certain urinary cotinine level indica tes a lower environmental tobacco smoke exposure in a; small child tha n in an adult.