Regular secondhand smoking by the children of 13 can affect arteries, according to the Finnish researchers. The study showed that the damage caused by secondhand tobacco smoke starts in childhood and causes considerable harm by teen years. The artery wall thickens by inhaling secondhand tobacco, which can result in heart attack.

"Although previous research has found that passive smoke may be harmful for blood vessels among adults, we did not know until this study that these specific effects also happen among children and adolescents", said Dr. Katariina Kallio of the University of Turku in Finland.

The research was based on 494 children aged 8 to 13. They measured levels of cotinine, which is a byproduct of nicotine, found in the blood after someone breathes in tobacco smoke

Children were divided into groups with high, intermediate and low cotinine levels. To measure the thickness of the aorta and of the carotid artery in the neck, Ultrasound was used. Artery walls look thicker in an ultrasound if they are spoiled by the process of atherosclerosis.

"These findings suggest that children should not face exposure to tobacco smoke at all. Even a little exposure to tobacco smoke may be harmful for blood vessels", said Dr. Katariina Kallio.