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A pacifier behind an ashtray and lit cigarette.

U researchers have found that cancer-causing chemicals from cigarette smoke can find their way into the lungs, bloodstreams, and urine of infants exposed to cigarette smoke.

Another reason to quit

A University study finds a tobacco-specific carcinogen in the urine of infants who inhale cigarette smoke

May 22, 2006

If you smoke and you've been meaning to quit, here's one more reason. A new study by the University Cancer Center has shown that cancer-causing chemicals from cigarette smoke find their way into the lungs, bloodstreams, and urine of infants exposed to cigarette smoke. Studying 144 infants of parents who smoked, the researchers detected NNAL, a cancer-causing chemical, in the urine of 47 percent. NNAL is produced as the body processes NNK, a carcinogen specific to tobacco. Some infants' NNAL levels were similar to levels found in adult smokers. Lead researcher Stephen Hecht says the chemicals clearly came from secondhand smoke. "There is no way that the observed high levels of cancer-causing chemicals associated with tobacco smoke could get into an infant's system other than by breathing in cigarette smoke," he says. "The level of NNAL detected in the urine of these infants was higher than in most other field studies of environmental tobacco in children and adults. Some of the infants had levels of NNAL similar to levels found in adult smokers." NNAL is an accepted biomarker for measuring the uptake of the tobacco-specific carcinogen NNK. It is found only in the urine of people exposed to tobacco smoke. As for the babies in whom NNAL was not found, Hecht says they probably also had NNAL in their urine, but too little for the researchers' detection methods to pick up The infants with detectable levels of NNAL lived with family members who reported smoking an average of 76 cigarettes per week in their home or car while the infants were present. In infants with undetectable levels of NNAL, family members reported smoking an average of 27 cigarettes per week. "Most importantly," says Hecht, "an infant one year in age or less is very close to the mother and father, so if the parent is smoking, it only makes sense that the infant is breathing in the smoke." Hecht further notes that smoking around an infant is typically the beginning of long-term exposure for that child to secondhand smoke. "Parents have the greatest impetus to quit smoking when they learn they are going to have a baby," he says. If the parents don't quit then, they are unlikely to quit any time soon after the baby is born. "These exposures could contribute to cancer risk later in life, although further biomarker studies would be necessary to investigate that relationship," the researchers conclude. "A broad range of potentially effective interventions to decrease exposure exists. These include efforts to encourage women to quit before or during pregnancy and to avoid postpartum relapse; to encourage smoking cessation among household members; and to establish no-smoking policies for the home and car. Evidence that nicotine is present in dust and surfaces of houses in which smoking takes places indicates that the complete elimination of smoking in homes is preferable to an emphasis on not smoking in the presence of children." This work expands on a previous study by Hecht and his colleagues that found newborn infants born to mothers who smoked took in the NNAL carcinogen directly from their mothers through their placenta. A comparison of results showed that the first urine from newborns whose mothers smoked during pregnancy contained as much as one-third more NNAL than infants in the current study. Collaborating with Hecht were Steven G. Carmella, Ky-Ahn Le, Sharon E. Murphy, Angela J.Boettcher, Chap Le, Joseph Koopmeiners, Larry An, and Deborah J. Hennrikus, all with the Cancer Center and its Transdisciplinary Tobacco Use Research Center. The results are published in the May issue of Cancer Epidemiology, Biomarkers and Prevention, a journal of the American Association for Cancer Research. The study was funded by a grant from the National Institute of Drug Abuse.

This story was adapted from a news release from the Academic Health Center and Cancer Center.