By LEE BOWMAN
Scripps Howard News Service
May 12, 2006
The study found "substantial uptake" of nicotine and the chemical NNAL in 67 of 144 infants, or 47 percent, and the levels were directly related to how much their parents smoked around them in the home or car. NNAL is a byproduct of a toxin in tobacco that's known to cause lung cancer.
"The take-home message is: Don't smoke around your kids," said Stephen Hecht, a cancer-prevention researcher at the University of Minnesota Cancer Center who led the study, published Friday in the journal Cancer Epidemiology, Biomarkers and Prevention.
Hecht and his team collected urine samples from the infants, ages 3 to 12 months, and interviewed parents about smoking habits. Eighty-two percent of the babies' mothers were daily smokers and 72 percent had other family members, including fathers, who smoked.
Parents or other family members of babies who had detectable levels of NNAL smoked an average of 76 cigarettes a week in the home or car with the infants present. Children with undetectable levels of the chemical had family members who smoked an average of 27 cigarettes near the babies each week. Nearly all the babies had detectable levels of nicotine, as well as cotinine, the byproduct that's left as the body metabolizes nicotine.
However, Hecht said that the difference likely reflects the limits the equipment used by the researchers. "With more sensitive analytical equipment, the NNAL from urine of babies in lower-frequency smoking households would most likely be detectable."
The infants' NNAL levels were higher than those seen in studies of adults exposed to secondhand smoke in the home.
"That's probably because infants are, at most times, closer to the source of the smoke," Hecht said. "Infants don't generally go that far from their parents, except when they're sleeping." He noted that while most of the exposure came directly from smoke in the air, it's also possible that the infants got some of the toxin by being close to clothes, bedding, rugs and upholstery permeated by cigarette smoke.
An earlier study by Hecht's team found that the first urine samples drawn from newborns whose mothers smoked during pregnancy had as much as one-third more NNAL as the top levels found in the babies in the current study. That's because the newborns got the chemical directly from their mothers through the placenta rather than breathing it in through secondhand smoke.
Although it's not clear from research so far how much the cancer-causing chemical affects a child's risk for cancer later in life, Hecht said the study makes it clear there's a potential that the chemical is being taken in by babies during their early years when they're growing rapidly.
"This begins a pattern of exposure that's likely to extend for the first 18 years of a child's life," Hecht said. "The findings certainly support the concept that persistent exposure to environmental tobacco smoke in childhood could be related to cancer later in life."
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