In another study on the effects of second-hand smoke, Japanese researchers sought to determine if short-term exposure to environmental tobacco smoke affected free-radical production in young, healthy nonsmokers.

Increasing evidence shows that second-hand smoke breaks down the antioxidant defenses, which is associated with impairment of the endothelial-dependent function of arterial walls. Endothelial dysfunction is an early feature of atherosclerosis, the disease process that underlies heart disease and stroke, and is an important marker of vascular damage.

Free-radicals, which are unstable molecules produced during a process called oxidation, can damage cells in the body. This damage is often called oxidative stress. It is significantly higher in children exposed to second-hand smoke.

To measure oxidation injury, the Austrian researchers examined levels of a biological compound called 8-epi-PGF2alpha in the blood and urine of 158 children (71 boys, 87 girls) ages 3 to 15. The compound is formed when free radicals attack arachidonic acid, a chemical whose normal function includes blood vessel dilation, blood clot prevention and inflammation reaction.

"It is a very potent blood vessel constrictor and may help create blood vessel spasm and set the stage for blood clot formation," says senior researcher Helmut F. Sinzinger, M.D., of the University of Vienna in Austria.

Children were grouped according to the smoking levels of their parents, whether both parents were smoking at home, and according to the number of cigarettes smoked each day. Researchers compared results to those from a nonsmoking control group.

Blood and urinary 8-epi-PGF2alpha levels were elevated if children were exposed to second-hand smoke by smoking parents. "Even if exposed to the second-hand smoke from less than 20 cigarettes a day by one smoking parent, levels were elevated in plasma by 35 to 50 percent and in urine by 20 to 30 percent," Sinzinger says.

Increasing the number of cigarettes smoked in the home correlated to higher levels of 8-epi-PGF2alpha, regardless of the child's age or gender. Researchers found that if parents were together smoking more than 40 cigarettes a day, blood 8-epi-PGF2alpha was as much as 130 percent higher than that of the control group and urinary 8-epi-PGF2alpha was about 65 percent higher than in the control group. Further, smoking by the mother had a significantly more pronounced influence.

"We speculate that mothers may have closer contact with their children at home," Sinzinger says. It's too early to speculate on measures other than recommending parents not smoke when their children are present.

"It is well known that atherosclerotic lesions on vascular tissue are strongly correlated to risk factors that include cigarette smoking," Sinzinger says. "Considering that in the United States and Western Europe nearly half of all children are exposed to second-hand smoke in some way, these findings could be of great importance. Later vascular disease might be triggered early in childhood by exposure to second-hand smoke."

In the Japanese study, researchers recruited 12 non-smoking men, average age 30, with no history of cardiovascular disease, high blood pressure or diabetes. They tested their levels of 8-epi-PGF2alpha and used ultrasound to measure endothelial function in subjects' brachial artery before and after a 30-minute exposure to environmental tobacco smoke. Flow-mediated dilation (FMD) is an inexpensive and safe way to evaluate endothelial function. It measures changes in the amount of blood flow through a particular blood vessel.

The endothelium is the inner lining of blood vessels. This thin layer of cells helps vessels expand and contract in response to different amounts of blood flow. If these cells are damaged, the blood vessels will be "stiff" and less able to handle the body's changing blood flow needs.

After exposure to tobacco smoke, the men’s blood levels of 8-epi-PGF2alpha significantly increased from an average of 20 picograms per milliliter (pg/mL) to 36 pg/mL. Their FMD decreased from 7.8 percent to 3.9 percent.

"These findings may add relevance to the idea that everyone should be protected from even short-term exposure to second-hand smoke," says lead researcher Toru Kato, M.D., Ph.D., of the division of cardiology at Saitama Medical Center, Saitama Medical School in Japan.

Co-authors of the Japanese study are Shunichi Sato, M.D.; Toshihiko Nishioka; Mikio Yuhara; Yoshiro Inoue; Hiroyuki Ito; Yoshiaki Maruyama; Shugo Tanaka; and Nobuo Yoshimoto, M.D., Ph.D.

Co-authors of the Austrian study are Anthony Oguogho, M.D., and Heidemarie Pilz, M.D.