Active and passive tobacco exposure.

Both passive and active exposure to tobacco smoke have adverse cardiovascular consequences for children and adolescents. Smoking as a habit begins in mid-adolescence and is perpetuated by the highly addictive nature of nicotine. Smoking has been associated with decreased life expectancy from all causes and early atherogenesis. The physiologic effects of active, and possibly passive smoke exposure include endothelial injury, increased oxidizability of LDL cholesterol, lower HDL cholesterol, impaired exercise performance, and altered oxygen delivery. Physician roles have been limited to research into the harmful nature of tobacco in the past, but new roles in advocacy against tobacco companies and the treatment of nicotine addiction are evolving.