Researchers say they've discovered significant levels of a known carcinogen in the urine of infants as young as three months, who have been exposed to second-hand smoke from their parents' cigarettes.

The new study, published in the May issue of Cancer Epidemiology, Biomarkers and Prevention, shows that researchers found levels of NNAL in 47 per cent of 144 babies aged three months to a year, who were exposed to their parents' smoking.

"The take home message is, 'Don't smoke around your kids,'" Stephen S. Hecht, the study's lead author and chair of cancer prevention at the University of Minnesota, said in a written statement.

"The level of NNAL detected in the urine of these infants was higher than in most other field studies of environmental tobacco smoke in children and adults," said Hecht.

NNAL is a cancer-causing compound produced in the human body as it processes NNK, a chemical specific to cigarette smoke.

NNAL has been shown to cause cancer of the lung, pancreas, liver and nasal cavities in laboratory animals.

Although a direct link to human malignancies has not been definitively proven, the International Agency for Research on Cancer considers this compound carcinogenic to humans, Hecht said.

Experts say that the study confirms tobacco-related toxins make their way from the lungs into other tissues of the body where they could have harmful effects.

When NNAL was detected in the urine of babies, family members smoked an average of 76 cigarettes per week in the presence of the infants.

The levels were typically between 1 per cent and 5 per cent of those found in smokers, although one child in the study had NNAL levels comparable to a smoker's.

Where NNAL levels were not observed, the average number of cigarettes smoked by family members was reported at 27 per week.

In questionnaires given to the mothers, 82 per cent reported being daily smokers and 72 per cent said they lived in households that included other tobacco users.

But Hecht warned that the detection test had limitations.

"With more sensitive analytical equipment, the NNAL from urine of babies in lower frequency cigarette smoking households would most likely be detectable," Hecht said.

Dr. Gideon Koren, a pediatrician and pharmacologist at Toronto's Hospital for Sick Children, said research at his centre more than a decade ago showed nicotine and cotinine are found in the hair of newborns whose mothers smoked during pregnancy.

"This is another marker," Koren told The Canadian Press of NNAL in urine. "Cigarette smoke has 1,400 different poisons and chemicals, some of them carcinogenic. And it all makes sense.

"If you are smoking near your kids or even in another room, it will go around through aeration. It's a real risk for children."

Scientists say there is no hard evidence that infants exposed to second-hand smoke will develop childhood cancer or malignancies in adulthood.

But there is proof in the medical literature that workers such as bartenders who are exposed to tobacco smoke over a long period of time will develop lung cancer.

"There's no reason to believe that will not be the case for small children, but convincing research is not yet out there," said Koren, noting that sudden infant death syndrome, respiratory infections and asthma are more prevalent among children living with smokers.

Koren pointed out that infants and children are captive to their parents' smoke.

They are particularly vulnerable to second-hand smoke because their rate of respiration is 40 times a minute on average, compared to about 12 in adults.

"Babies breathe a lot more rapidly than adults do, and what's more, they're also growing quickly and so they're absorbing lots more into the body and they're more fragile in terms of development and so on," Francis Thompson of the Non-Smokers' Rights Association said, appearing on CTV Newsnet.

"So it's not surprising that the impact of second-hand smoke on babies is likely to be larger," he said.

Koren questioned why parents are permitted to smoke in front of their children when they can't smoke at work.

"Just think about it: try to smoke at work anywhere in Canada today and you are against the law," Koren told CP. "The same individual can go home and smoke in the face of a two-month-old and he's not against the law.

"How come we cannot smoke near our fellow workers, but we can do it to our children?"

Thompson believes parents are putting their children at risk not because they don't care, but because they are grappling with addiction.

"I you're addicted to tobacco, you've been hearing for years it's very, very bad for you, the smoker, and you've been trying hard to live with that... you've probably been trying to quit fairly often and haven't succeeded," he said.

'It's very hard to accept when you're addicted to it that it can also be harming those around you. It creates a lot of anxiety, and people react to anxiety in different ways and one way they react to anxiety is just to try to ignore the issue."

Source: The Canadian Press