Children ages 2 to 14 who are exposed to secondhand smoke show signs of cardiovascular injury, meaning they may be at increased risk of heart disease, HealthDay News reported March 13.

Researchers took hair samples from 125 children and checked them for nicotine exposure, then took blood samples to look for a cellular marker for cardiovascular health called EPC. They found that toddlers tended to have the greatest levels of nicotine exposure -- six times that of older children -- as well as greater indicators of cardiovascular risk.

"Toddlers are smokers by default," said study co-author John Bauer, director of the Center for Cardiovascular Medicine at Nationwide Children's Hospital and Research Institute in Columbus, Ohio. "Forty percent of toddlers in our study had nicotine content that in adults would suggest that they were active smokers. But, an active smoker has a filter on cigarettes. The toxicity from smoke that is inhaled in the atmosphere is worse because there's no filter."

"Toddlers are like fish in a fish bowl," added Bauer. "They're strapped pretty closely to their parental units, which exposes them to more smoke than adolescents who live in the same set of circumstances." Researchers also noted that toddlers breath more rapidly, thus inhaling more smoke than older children.

The findings were presented at the American Heart Association's recent Cardiovascular Disease Epidemiology and Prevention meeting in Colorado Springs, Colo.