A University of Minnesota Cancer Center study shows that infants inhale the cancer-causing chemicals found in secondhand smoke, providing further evidence that parents should not smoke around their children.
"There is no other 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," said Stephen Hecht, Ph.D., University of Minnesota Cancer Center tobacco researcher and lead investigator of this study.
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.
Hecht and his colleagues examined urine samples from 144 infants, all younger than one year. They found detectable levels of cancer-causing NNAL (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol) in the urine of 47 percent of the infants exposed to cigarette smoking by family members. NNAL is a chemical produced in the human body as it processes NNK, a carcinogenic chemical specific to tobacco.
"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," Hecht said. "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.
In this study, infants with detectable levels of NNAL lived with family members that 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 in their urine, family members reported smoking an average of 27 cigarettes per week.
"In all probability, these infants also had NNAL in their urine, but our detection methods were not sensitive enough to pick it up," Hecht said. "Most importantly, 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 noted 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. If the mother doesn't quit then, it is unlikely she will quit any time soon after the baby is born," he said. "The same holds true for the father of the child."
This study 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 this current study.
Hecht conducted this study in collaboration with 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 University of Minnesota Cancer Center and its Transdisciplinary Tobacco Use Research Center.
