A University Cancer Center study suggests that exposing infants to secondhand smoke could contribute to cancer risks later in life.

Researchers studied the urine of 144 infants exposed to cigarette smoke by family members and found cancer-causing chemicals called NNAL in almost half of the infants. NNAL is a metabolite of a carcinogen found in tobacco smoke.

“The greater the reported number of cigarettes the baby was exposed to, the higher the levels of the carcinogens,” said Deborah Hennrikus, associate professor in the division of epidemiology and community health in the school of public health.

She said more carcinogens were found in infants than in other studies of adults and older children exposed to secondhand smoke.

“Babies are kind of a captive audience,” she said. “They’re at home and they’re with their mother a lot of the time, so if the mother is smoking around them, there is no avoiding it.”

The higher exposure may also be caused by infants breathing faster than adults, Hennrikus said. Infants also breathe more through their mouth, which doesn’t filter the air as much.

“I think people don’t quite realize the extent of damage that they can do to children by smoking around them,” she said.

Stephen Hecht, a researcher at the Cancer Center and the lead investigator of the study, has also done previous research that found newborns born to smoking mothers took in carcinogens directly from their mothers through the placenta.

“There are many documented (negative) effects of smoking during pregnancy,” Hecht said. “There’s no way that smoking can be good for your baby.”

According to the American Cancer Society, more than 10 percent of pregnant women smoke throughout their pregnancies.

Smoking during pregnancy has been linked to low birth weight in babies.

The society also reported that infants of women who smoke during pregnancy are two to three times more likely to die from sudden infant death syndrome.

Matthew Flory, Minnesota health promotions director for the American Cancer Society, said Hecht’s research “suggests that there may be another reason to quit smoking which is that you don’t want to pass on cancer risk to your children.”

Hennrikus said many pregnant women quit smoking during their pregnancy, but most relapse after the child is born.

“Stopping smoking at any time during the pregnancy is a good idea,” Hennrikus said. “The more you smoke, the more dangerous it is for the fetus – it’s just really a bad thing to do.”

Though it may seem like common sense, women continue to smoke during pregnancy and around their children, said Sharon Murphy, associate professor in the department of biochemistry, molecular biology and biophysics. She said this type of research helps to document the obvious.

“To actually have some numbers just makes it much more concrete,” Murphy said. “If we could show significant exposure in the children, then that’s going to be useful feedback to encourage (mothers) to eventually quit.”

Hecht said legislation and awareness of the effects of secondhand smoke has reduced the prevalence of smoking. He said states that have taken aggressive initiatives, such as Massachusetts, have seen a decrease in smoking.

The Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report shows further evidence of this. From 1990 to 2002, the percentage of mothers who smoked during pregnancy in Massachusetts dropped 68 percent.

Flory said the University’s research makes it clear that there’s not only a risk to the mother, but also a risk for the child as well.

“You have a certain incentive for yourself, and probably a double incentive for your child,” he said.

Hecht plans to continue researching the effects of secondhand smoke.

“I think it’s important to keep this issue in the public eye,” he said. “Legislation and attention to secondhand smoke has an effect on smoking overall, and that’s one reason we keep doing these studies.”