A new international study of more than 20,000 children confirms that exposure to cigarette smoke before and after birth impairs their lung function, and that parental smoking remains a serious public health issue.

The effects of smoking during pregnancy last up to age 12, while exposure to cigarette smoking after birth further worsens lung function, Dr. Manfred A. Neuberger of the Medical University in Vienna, one of the study’s authors, told Reuters Health.

It is difficult to tell, Neuberger noted, whether the impairment of lung function resulting from prenatal and early life exposure is permanent, given that many individuals with parents and siblings who smoke will have started smoking themselves by their teen years.

The researchers analyzed results from a subset of children who had participated in the Pollution and the Young Study, including a total of 22,712 children from eight countries. The findings appear in the American Journal of Respiratory and Critical Care Medicine.

Children whose mothers smoked during pregnancy were 31 percent to 40 percent more likely to have poor lung function than children born to non-smokers, the researchers found. Early-life exposure independently increased risk of poor lung function to a lesser degree, by 24 percent to 27 percent.

Sixty percent of the children in the study had been exposed to cigarette smoke before birth or in early life, the researchers found. “Considering the high number of exposed children, this indicates that both environmental tobacco smoke exposure and smoking during pregnancy remain a severe public health problem,” Neuberger and his team conclude.

The findings are a “stark reminder” that legal efforts to reduce exposure to cigarette smoke in workplaces aren’t protecting the group of people at greatest risk from passive smoking, young children, Drs. Mark D. Eisner of the University of California, San Francisco and Francesco Forastiere of the Rome E Health Authority in Italy write in an editorial accompanying the study.

“Children are primarily exposed to tobacco smoke in the home, where legal restrictions do not apply,” they note.

SOURCE: American Journal of Respiratory and Critical Care Medicine, June 2006.